Article: 219481 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <9Amhf.24745$Zv5.22006@newssvr25.news.prodigy.net> Message-ID: Date: Fri, 25 Nov 2005 05:26:52 GMT Dave Heil wrote: > Cecil Moore wrote: >> I made the mistake at RS of asking for a Molex connector. > > They actually have a few of 'em, Cecil. Our area stores keep them in > metal drawers now rather than hanging them on the wall. Oh, they had them hanging on the wall but said they didn't have any. When I found them, they asked, "How do you know that's a Molex connector?" :-) Adopted from the IC-22S 30 years ago, I still use the 4-pin version for low current 12 volt power in my shack and in my pickup. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219482 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Fri, 25 Nov 2005 00:46:57 -0800 Message-ID: <11odjs54affpl83@corp.supernews.com> References: Most authors explain how a wave is generated, then resort to reciprocity to explain the reception process. But a clear and simple direct explanation appears in Bailey, _TV and Other Receiving Antennas_ (pp. 141-2), of what happens when an electromagnetic wave strikes a conductor: "The second, and equally important effect [the first being reflection of much of the incident energy] is that some energy /does/ enter the outer skin of the conductor. That part of the energy, which is not reflected, must enter the conductor. The conditions at the surface of the conductor, as we have already seen, give rise to a small resultant electric vector and a large resultant magnetic vector. The presence of these at the conductor is direct evidence that power is entering the conductor. The small electric vector acts on the internal electrons of the conductor and impresses a direction force, tending to drive the electrons along the skin of the conductor in the direction of the electric vector. But from experience we know that /no/ electrons can ever be caused to move without gradually establishing their own magnetic field, and this usually takes /time/. The motion of electrons (which is electric current by definition) never takes place without the magnetic field. How, then, is the electric vector from the electromagnetic wave going to put these electrons in motion? It can only do so because the electromagnetic wave /also supplies a magnetic vector/ as well as an electric vector. And the value of this magnetic vector is exactly proportioned to supply just the right amount of magnetic field energy which the electrons require for immediate motion. Thus the electrons do not have to establish their own magnetic field, since this field is supplied by the electromagnetic wave. Hence, electromagnetic wave energy entering the conductor establishes immediate motion of electrons /along/ the conductor, the direction of motion at any instant corresponding to the direction of the electric vector. If the electric vector changes direction, the electrons will follow suit." Other posters have correctly pointed out that an antenna doesn't and can't receive a signal solely due to the E field; a time-changing E field can't exist without an accompanying time-changing H field. Roy Lewallen, W7EL Paul Taylor wrote: > Hi, > > I am looking for an explanation of how an antenna receives a signal due > to the E-field of an electromagnetic wave. > > I have looked in some books, and can understand transmission, but the > books I have looked in don't explain reception. > > I have found an explanation of how the H-field induces a signal in a loop > antenna: a changing magnetic flux will induce a current. > > But what about the E-field and a dipole antenna? I guess that the E-field > causes electrons to move in the antenna wire, because in a solid > conductor, electrons will move until the E-field inside the solid is > cancelled out? > > I have googled but having difficulty finding a good explanation. Any > pointers? > > Thanks & regards, > > Paul. > Article: 219483 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: Radio Shack and my education Date: Fri, 25 Nov 2005 09:55:12 -0800 Message-ID: <11oek0b8to2mm42@corp.supernews.com> References: <43865eea$0$32203$39cecf19@news.twtelecom.net> It's interesting you mention that, Tom. I just got my Extra last month. Now, I admit I am not an electronics expert. I had to study really hard before I felt I could take the test. What was funny was actually taking the test. There were a total of six people testing. Myself and five others. Two going for Technician, two going for General, and two going for Extra (myself and one other guy I didn't know). So, I'm pounding away on the calculator and the other Extra finishes before anyone. He must have only taken ten minutes, if that. He had to of memorized the answers. Actually there were a total of three people who had to have memorized the questions. No way they could have finished so fast. Actually, I was the only one who brought a calculator, so that tells you something. What was really interesting to me was that the other Extra had now passed all the writtens, but had never passed the 5 WPM code test. So, no HF priveleges until he does that. I was licensed fifteen years ago and got up through Advanced and took the code tests. But I moved out of state and never got around to taking the Extra. Now, it's all changed and there are only three tests. Anyway, interesting experience. Rod KI7CQ Article: 219484 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: Radio Shack and my education Date: 25 Nov 2005 18:10:47 GMT Message-ID: References: <11ocbjrd4j4ar74@corp.supernews.com> <6Trhf.46856$Hs.45544@tornado.socal.rr.com> <438737BB.D753827A@shaw.ca> On Fri, 25 Nov 2005 16:11:28 GMT, Irv Finkleman wrote: > Phil Wheeler wrote: >> Michael wrote: >> > My son took and electronics course at Benson High School in Portland Oregon. >> > The teacher was totally clueless and just made things up as he went along. >> >> Ah yes. I attended Bensen Tech (so it was called then) in the Fall of >> 1953. We were taught to check light sockets for electricity be removing >> the bulb and putting our fingers in them. Harmless fun :-) > > I couldn't wait to be old enough to go to tech so I tried the light > socket test at home at age 7. Thus begun my lifetime love of communications > and electronics! The results of the experiments proved so valid that I never > again had the need to revalidate! I built my first light bulb at the age of 8 -- I used a test tube >from a chemistry set of mine and about 10" of bare copper wire that I found in my dad's ham shack (the original W3DHJ). Hell, it sure looked a lot like a light bulb! Then I poked it into the wall outlet in my bedroom. BIG TIME mistake! I was an Army Brat and we were living in conscripted housing in Bremerhaven, Germany at the time.... Thus began my lifetime love of of all things electronical. (-: I suppose this OT thread should be in rec.radio.amateur.homebrew. :-) Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 219485 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Subject: Re: Radio Shack and my education Message-ID: Date: Fri, 25 Nov 2005 19:01:54 GMT "Rod Maupin" wrote in message news:11oek0b8to2mm42@corp.supernews.com... > It's interesting you mention that, Tom. > > I just got my Extra last month. Now, I admit I am not an electronics > expert. I had to study really hard before I felt I could take the test. > What was funny was actually taking the test. > > There were a total of six people testing. Myself and five others. Two > going for Technician, two going for General, and two going for Extra (myself > and one other guy I didn't know). So, I'm pounding away on the calculator > and the other Extra finishes before anyone. He must have only taken ten > minutes, if that. He had to of memorized the answers. Actually there were > a total of three people who had to have memorized the questions. No way > they could have finished so fast. Actually, I was the only one who brought > a calculator, so that tells you something. > > What was really interesting to me was that the other Extra had now passed > all the writtens, but had never passed the 5 WPM code test. So, no HF > priveleges until he does that. > > I was licensed fifteen years ago and got up through Advanced and took the > code tests. But I moved out of state and never got around to taking the > Extra. Now, it's all changed and there are only three tests. > > Anyway, interesting experience. > > Rod KI7CQ > Instead of studying electronics you should have been studying the qusetion and answer book. When the questions are the same as in the book , it is no use learning anything for a test. I had the tech license for about 25 years. Just did not want to take time for the code and did not care anything for the lowbands anyway. The job I had gave me some free time on the night shift so I finally decided to take in some code tapes and learn the code on company time. Went to Advanced and about a year later the Extra. I never did get a chance to look at the Q&A book. I did not need a calculator fo rthe tests. The answers are usualy broad enough you can almost guess at them and a quick check with a pencil and paper will do. I have not seen the new Extra exam but the old one was very easy compaired to the old Advanced exam. By the way, in 1972 when I took the First Class Phone license there were no calculators or Q&A books with the exect Q&As. Article: 219486 of rec.radio.amateur.antenna From: Paul Taylor Subject: Re: Antenna reception theory Date: Fri, 25 Nov 2005 19:08:54 +0000 Message-ID: References: Hi, Thanks for the replies. I also found a sentence in Joseph Carr's book, Practical Antenna Handbook second edition. On page 297: 'Large loop antennas are sensitive primarily to the electric field of the electromagnetic radio wave, but small loop antenna are primarily sensitive to the magnetic field of an EM wave.' I understand that the receiver antenna works in a reciprocal way to transmit, but if there are other descriptions out there concentrating on how antennas work at the receiving end, I would be interested to know. Regards, Paul. -- Remove _rem_ before replying by email. Article: 219487 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <438663b1$0$3759$39cecf19@news.twtelecom.net> Subject: Re: Happy Thanksgiving Date: Fri, 25 Nov 2005 14:24:42 -0500 Message-ID: <2902a$438764ff$97d56a33$4854@ALLTEL.NET> Exactly what we had for dinner... Turduken is the best eating there is! "Tom Ring" wrote in message news:438663b1$0$3759$39cecf19@news.twtelecom.net... > Fred W4JLE wrote: > > > A happy Thanksgiving to all... May your day be a joyous one with friends and > > family. > > > > 73 Fred W4JLE / NNN0AAG > > > > > > Mmmmmmmmm, Turducken.... > > tom > K0TAR > Article: 219488 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Message-ID: Date: Fri, 25 Nov 2005 19:35:07 GMT Cecil Moore wrote: > Rod Maupin wrote: > >> So, I'm pounding away on the calculator and the other Extra finishes >> before anyone. He must have only taken ten minutes, if that. He had >> to of memorized the answers. > > > Rod, I finished that trivial Extra exam in 10 minutes and > I can assure you, with a EE degree and MENSA membership, > I didn't memorize the answers. But it does happen. Back in the 20 WPM days, maybe ten years ago, one ham I know .. who was a former Navy telegraph op .. passed the written part by memorizing every Q&A. And it showed: He was a technical know-nothing. Nice guy, though. Phil Article: 219490 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: Radio Shack and my education Date: Fri, 25 Nov 2005 11:41:47 -0800 Message-ID: <11oeq7qtm6m523f@corp.supernews.com> References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Well, that's impressive to me. I didn't know anything about electronics until I became a ham. I still don't know much. I know how to set up a station and how to put out a clean signal. But I don't know enough to build anything. Which is a shame. Seems like there are a lot of fun projects out there. Rod KI7CQ Article: 219491 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <11oeq7qtm6m523f@corp.supernews.com> Message-ID: Date: Fri, 25 Nov 2005 19:50:52 GMT Rod Maupin wrote: > Well, that's impressive to me. > > I didn't know anything about electronics until I became a ham. I still > don't know much. I know how to set up a station and how to put out a clean > signal. But I don't know enough to build anything. Which is a shame. > Seems like there are a lot of fun projects out there. > > Rod KI7CQ > There are. You should checkout the Elecraft website: Fun! Article: 219492 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <11ocbjrd4j4ar74@corp.supernews.com> <6Trhf.46856$Hs.45544@tornado.socal.rr.com> <438737BB.D753827A@shaw.ca> Message-ID: Date: Fri, 25 Nov 2005 21:45:07 GMT Amos Keag wrote: > Allodoxaphobia wrote: > > SNIPPED > >> >> >> I built my first light bulb at the age of 8 -- I used a test tube >> from a chemistry set of mine and about 10" of bare copper wire that >> I found in my dad's ham shack (the original W3DHJ). Hell, it sure >> looked a lot like a light bulb! Then I poked it into the wall outlet >> in my bedroom. BIG TIME mistake! I was an Army Brat and we were >> living in conscripted housing in Bremerhaven, Germany at the time.... >> Thus began my lifetime love of of all things electronical. >> >> (-: I suppose this OT thread should be in rec.radio.amateur.homebrew. >> :-) >> >> Jonesy > > > OR: rec.radio.amateur.need.insurance > Funny! Phil W7OX Article: 219493 of rec.radio.amateur.antenna From: "Old Ed" References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Subject: Re: Radio Shack and my education Message-ID: Date: Sat, 26 Nov 2005 01:01:05 GMT "Cecil Moore" wrote in message news:afJhf.20616$7h7.15873@newssvr21.news.prodigy.com... > Rod Maupin wrote: > > So, I'm pounding away on the calculator > > and the other Extra finishes before anyone. He must have only taken ten > > minutes, if that. He had to of memorized the answers. > > Rod, I finished that trivial Extra exam in 10 minutes and > I can assure you, with a EE degree and MENSA membership, > I didn't memorize the answers. > -- > 73, Cecil http://www.qsl.net/w5dxp Cecil, I'm glad you passed your Extra exam without difficulty. But I have to point out that there are many exam questions not covered in EE (e.g., band breaks and OSCAR schemes); and NONE of the exam questions are covered in MENSA. Thus at least some memory work is needed. I have three EE degrees (and could readily "qualify" for MENSA); but I nevertheless studied quite diligently for the Extra exam (2001). I was gratified to get 100%, but I readily admit taking more than 10 minutes. 73, Ed, W6LOL Article: 219494 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Subject: Re: Radio Shack and my education Message-ID: <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> Date: Sat, 26 Nov 2005 02:43:08 GMT > > Instead of studying electronics you should have been studying the qusetion > > and answer book. When the questions are the same as in the book , it is no > > use learning anything for a test. > > Where do you get that, Ralph? That license isn't the final goal. It's > the beginning. If all a person wants to do is pass some test, I suppose > they could memorize Q and A. - although I might postulate that > memorizing over 800 questions for the Extra might be harder than simply > learning the material. > > Getting the license is the first goal. You have to memorize the rules to answer many of the questions. Might as well memorize the other parts too. You get your license and you can start to learn about ham radio. Sometimes the questions can be deceiving and what may be a correct answer may not be the "best" answer. As far as getting good answers about most anything at RAdio Shack or many other stores , what do you expect from someone making the wages they pay ? You do not get a salesman and electronics engineer for those wages. Try going into any store, say Wal-Mart and pick out an area and ask some specific questions about the products and see what they have to say. Chances are you will get the same dumb look and maybe a dumb answer. Article: 219495 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> Message-ID: Date: Sat, 26 Nov 2005 03:40:55 GMT Old Ed wrote: > But I have to point out that there are many exam questions not > covered in EE (e.g., band breaks and OSCAR schemes); Dang, Ed, I just developed the OSCAR schemes from first principles. ;-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219496 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: SWR again. Date: Fri, 25 Nov 2005 23:34:44 -0500 Message-ID: <11ofpdpioimdg06@corp.supernews.com> References: This is getting a bit far from antennas, but the way to know the uncertainty in knowing time is to have multiple clocks. NBS (whatever it now calls itself) has a bunch of clocks that are compared to each other. When I was young (and WWV was back East) the uncertainty indicated from multiple clocks was a few parts in ten to the eighth power. Today, that uncertainty is a few parts in ten to the 13th power! It takes multiple clocks to know the uncertainty. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net "Michael Coslo" wrote in message news:dm2gb7$1f72$1@f04n12.cac.psu.edu... > > > A man with a watch knows the time. > > A man with two watches is never sure...... > > > > - Mike KB3EIA - > Article: 219497 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Radio Shack and my education Date: Fri, 25 Nov 2005 20:34:10 -0800 Message-ID: <11ofpe5kh28mk09@corp.supernews.com> References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> Ralph Mowery wrote: > . . . > As far as getting good answers about most anything at RAdio Shack or many > other stores , what do you expect from someone making the wages they pay ? > You do not get a salesman and electronics engineer for those wages. Try > going into any store, say Wal-Mart and pick out an area and ask some > specific questions about the products and see what they have to say. > Chances are you will get the same dumb look and maybe a dumb answer. One of the reasons this is the only choice we have is that in times past, there were stores which did pay the employees enough to get people who understood the products. People would go in, get their questions answered, then go to the Wal-Marts and Radio Shacks to buy the item because it was cheaper there. We've gotten what we created and what we collectively deserve. Roy Lewallen, W7EL Article: 219498 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> <11ofpe5kh28mk09@corp.supernews.com> Message-ID: Date: Sat, 26 Nov 2005 04:43:06 GMT Roy Lewallen wrote: > Ralph Mowery wrote: > >> . . . >> As far as getting good answers about most anything at RAdio Shack or many >> other stores , what do you expect from someone making the wages they >> pay ? >> You do not get a salesman and electronics engineer for those wages. Try >> going into any store, say Wal-Mart and pick out an area and ask some >> specific questions about the products and see what they have to say. >> Chances are you will get the same dumb look and maybe a dumb answer. > > > One of the reasons this is the only choice we have is that in times > past, there were stores which did pay the employees enough to get people > who understood the products. People would go in, get their questions > answered, then go to the Wal-Marts and Radio Shacks to buy the item > because it was cheaper there. We've gotten what we created and what we > collectively deserve. > Thanks for the reminder, Roy. But that has been a long while. Phil w7ox Article: 219499 of rec.radio.amateur.antenna From: "Denton" Subject: Re: can I make this 20 meter antenna work on 30 also? Date: Fri, 25 Nov 2005 21:51:08 -0800 Message-ID: <11oftujtfb44t98@corp.supernews.com> References: <1132981239.429441.291730@g47g2000cwa.googlegroups.com> Here is one little trick I tried a couple of years ago, when I had an elevated 20 meter vertical with the feed point about 10 feet in the air with 4 16 ft radials. I fed it at the base with a 4 to 1 balun, mounted in reverse. I then ran 450 ohm twin lead to the shack with a Johnson Matchbox to tune the feeders..it worked 40 thru 10 meters (some loss on 40 but it did work there ok). If you try this..you need to do something to keep the twin lead from swinging in the wind..or the impendence will change quite a bit. wrote in message news:1132981239.429441.291730@g47g2000cwa.googlegroups.com... > All, > > I'm finally putting together a vertical antenna that I hope will work > on 20 meters. > > Soil is sandstone with occasional bits of granite, impossible to drill > into, it has to be > chiseled out with a hand pickaxe. I won't begin to tell you the agony > involved in > chipping out a 2 1/2 foot cubic hole into this stuff, but I managed to > do it. > > But in any case forget about soil conductivity, and forget about ground > rods! There > is a single ground rod courtesy of the electrical company... probably > not at good > depth for RF but it is the only game in town. > > Construction: > > The ground half of the antenna starts with 5 foot of 1 inch diameter > iron pipe, > sunk halfway into hole filled with concrete. 2 1/2 half feet of iron > pipe are exposed > above the dirt. This is connected to 10 foot of 3/4 inch copper pipe. > > > At the 12 foot level I am mounting 4 radials, 8 foot 1 1/2 inches in > length, of 1/2 inch > diameter copper pipe. I am also mounting 4 copper guy wires, same > length, that are > intended to also work as additional radials. > > The radiative half of the antenna starts with 10 foot of 3/4 copper > pipe, topped with > a 9 foot carbon fiber fishing pole. A thin copper wire of about 6 foot > 3 inches in length > will be run up the fishing pole, for a total length of 16 foot 3 > inches. I will be mounting > rope guy wires on the botttom of the radiative half. > > The ground half and radiative half are connected together with a PVC > coupler, and make > contact with each other inside the coupler via a thick styrofoam > spacer. > > Question: > > This antenna is designed to hopefully work on 20 meters. If I run a > wire of 14 feet 4 1/2 inches up the fishing pole instead of the 6 foot > 3 inches, and if I use guy wires of 12 foot 2 1/4 inches, leaving the > radial lengths unchanged: will I get a vertical that I can work on > both 30 and 20 meters? > > Thanks in advance, > > The Eternal Squire > Article: 219500 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> Message-ID: Date: Sat, 26 Nov 2005 14:44:36 GMT Mike Coslo wrote: > Ralph Mowery wrote: > >>>> Instead of studying electronics you should have been studying the >> >> >> qusetion >> >>>> and answer book. When the questions are the same as in the book , >>>> it is >> >> >> no >> >>>> use learning anything for a test. >>> >>> >>> Where do you get that, Ralph? That license isn't the final goal. It's >>> the beginning. If all a person wants to do is pass some test, I suppose >>> they could memorize Q and A. - although I might postulate that >>> memorizing over 800 questions for the Extra might be harder than simply >>> learning the material. >>> >>> >> >> >> Getting the license is the first goal. You have to memorize the rules to >> answer many of the questions. Might as well memorize the other parts >> too. >> You get your license and you can start to learn about ham radio. > > > Hmmm, I suspect that someone who wanted to learn about ham radio > would start that process during the preparations for the test. Those who > would want to memorize entire question pools probably won't be too > interested in actually learning anything both before or afterward the > memorization. As well as not too bright. > I've seen it done both ways. And I've seen "rote learners" blossom in their knowledge and breadth of the hobby after getting licensed that way. Also the opposite. Since it is a hobby, what works for the individual seems to be all that is important. Phil w7ox Article: 219501 of rec.radio.amateur.antenna Date: Sat, 26 Nov 2005 09:09:20 -0600 From: Tom Ring Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> <11ofpe5kh28mk09@corp.supernews.com> Message-ID: <43887aa0$0$32199$39cecf19@news.twtelecom.net> Roy Lewallen wrote: > > One of the reasons this is the only choice we have is that in times > past, there were stores which did pay the employees enough to get people > who understood the products. People would go in, get their questions > answered, then go to the Wal-Marts and Radio Shacks to buy the item > because it was cheaper there. We've gotten what we created and what we > collectively deserve. > > Roy Lewallen, W7EL Support your local hardware store, support your local ham store.... I have paid a slight price penalty plus state and local tax to buy from my local ham store for almost 20 years. I can also sometimes get break when I have a rig that needs fixing 3 days before a contest or trip to FL and the service wait sign says "3 weeks". Buy local if you want good service from people you know and who know you. Tom K0TAR Article: 219502 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> Message-ID: Date: Sat, 26 Nov 2005 15:14:27 GMT Phil Wheeler wrote: > I've seen it done both ways. And I've seen "rote learners" blossom in > their knowledge and breadth of the hobby after getting licensed that > way. Also the opposite. At 14 years of age in 1952, I had little choice except to mostly memorize the 90 or so general class questions and answers in The License Manual. Being an amateur radio operator is what motivated me through a EE degree and a long career in electrical engineering. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219503 of rec.radio.amateur.antenna From: "RB" Subject: is voltage balun right choice? Message-ID: Date: Sat, 26 Nov 2005 09:33:02 -0600 I've recently put up a 140' dipole fed with ladderline. My tuner is separate from my rig, and is an unbalanced unit. So, I use a balun on the tuner output to hook the ladderline to. I've been told that I should have a voltage balun in this application. I was surprised to hear this, as I expected to hear use a current balun. Is the voltage balun the right one for this application? Article: 219504 of rec.radio.amateur.antenna From: ehramm@dk3uz.ampr.org (Edmund H. Ramm) Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> <11ofpe5kh28mk09@corp.supernews.com> Message-ID: Date: Sat, 26 Nov 2005 13:58:49 GMT In <11ofpe5kh28mk09@corp.supernews.com> Roy Lewallen writes: > [...] > One of the reasons this is the only choice we have is that in times > past, there were stores which did pay the employees enough to get people > who understood the products. People would go in, get their questions > answered, then go to the Wal-Marts and Radio Shacks to buy the item > because it was cheaper there. We've gotten what we created and what we > collectively deserve. Full ACK. This el-cheapo mentality hurts economy. 73, Eddi ._._. -- e-mail: dk3uz AT darc DOT de | AMPRNET: dk3uz@db0hht.ampr.org If replying to a Usenet article, please use above e-mail address. Linux/m68k, the best U**x ever to hit an Atari! Article: 219505 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: is voltage balun right choice? References: Message-ID: Date: Sat, 26 Nov 2005 15:55:55 GMT RB wrote: > I've recently put up a 140' dipole fed with ladderline. My tuner is > separate from my rig, and is an unbalanced unit. So, I use a balun on the > tuner output to hook the ladderline to. > > I've been told that I should have a voltage balun in this application. I > was surprised to hear this, as I expected to hear use a current balun. > > Is the voltage balun the right one for this application? Only if you want your feedline currents to be unbalanced. Your antenna is a lot like the one described on my web page below that uses a 1:1 choke-current-balun and needs no conventional tuner, the most efficient configuration I could come up with. As can be seen from the current maximum point graph on my web page, ~100 feet is a good compromise length for the ladder-line for such an antenna. A lot of hams will tell you to throw up a random length of ladder-line and feed it through a 4:1 voltage balun. That's usually not good advice and often results in a poor balun function on one or more bands. If one doesn't know approximately what impedance is being seen by the balun, one cannot predict if it will function or not. The free version of EZNEC can predict the approximate impedance seen by the balun. www.eznec.com -- 73, Cecil http://www.qsl.net/w5dxp/notuner.htm Article: 219506 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> <11ofpe5kh28mk09@corp.supernews.com> Message-ID: Date: Sat, 26 Nov 2005 15:57:31 GMT Edmund H. Ramm wrote: > Full ACK. This el-cheapo mentality hurts economy. Some TV or cable station is advertising a program called: "Is Walmart good or bad for the country?" -- 73, Cecil http://www.qsl.net/w5dxp Article: 219507 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> Message-ID: Date: Sat, 26 Nov 2005 17:25:04 GMT Cecil Moore wrote: > Phil Wheeler wrote: > >> I've seen it done both ways. And I've seen "rote learners" blossom in >> their knowledge and breadth of the hobby after getting licensed that >> way. Also the opposite. > > > At 14 years of age in 1952, I had little choice except to > mostly memorize the 90 or so general class questions > and answers in The License Manual. Being an amateur radio > operator is what motivated me through a EE degree and a long > career in electrical engineering. Similar to my history. General Class at 16 in 1953. That motivated me to get (eventually) three degrees in EE. Extra Class came 40+ years later when I finally wrenched my code speed up to a reliable 20 WPM .. not that it would matter now :) 73, Phil w7ox Article: 219508 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oek0b8to2mm42@corp.supernews.com> <0ZPhf.5587$wf.1166@newsread3.news.atl.earthlink.net> <11ofpe5kh28mk09@corp.supernews.com> Message-ID: Date: Sat, 26 Nov 2005 17:26:08 GMT Edmund H. Ramm wrote: > In <11ofpe5kh28mk09@corp.supernews.com> Roy Lewallen writes: > > >>[...] >>One of the reasons this is the only choice we have is that in times >>past, there were stores which did pay the employees enough to get people >>who understood the products. People would go in, get their questions >>answered, then go to the Wal-Marts and Radio Shacks to buy the item >>because it was cheaper there. We've gotten what we created and what we >>collectively deserve. > > > Full ACK. This el-cheapo mentality hurts economy. > Yeah .. like buying rigs made in some other country :) Article: 219509 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: 30/20 vertical? References: <1133023175.424981.104610@g43g2000cwa.googlegroups.com> Message-ID: <%w2if.33945$6e1.9744@newssvr14.news.prodigy.com> Date: Sat, 26 Nov 2005 19:17:15 GMT eternalsquire@comcast.net wrote: > If I add another 4 radials cut an eight wavelength for 30m, will it be > easier to operate on 30? Doesn't much matter if they are buried radials. I'm wondering if a short vertical with long elevated radials would result in an "off-center-fed" vertical. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219510 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: is voltage balun right choice? Date: Sat, 26 Nov 2005 20:17:16 +0000 (UTC) Message-ID: References: Cec, As an aside, there appears to be a little confusion about the various uses of baluns which arises from their uncertain perhaps misleading descriptions. Because of the way balun winding-wires are run, they are often described as transmission line transformers. There are -- Voltage Baluns, Current Baluns and Choke baluns. As I see it, Voltage Baluns have a definite voltage/impedance/turns ratio and are true impedance transformers. They may be used as either balanced-to-unbalanced windings, or be balanced-to-balanced, or be unbalanced-to-unbalanced. Balanced windings may be centre-tapped. One winding may be common to both primary and secondary windings. Choke Baluns consist of a pair of wires wound together around a ferrite core. The two wires may be of coaxial form or may consist of a twisted pair or just a pair of wires laid alongside each other. The two wires together form a transmission line of calculable impedance and loss. But a Choke Balun hss no impedance or voltage ratio. It is incorrect to refer to it as having an impedance ratio such as 1-to-1. A Choke Balun does indeed behave as an impedance transformer from one end of its line to the other. But the transformation ratio is indeterminate. The ratio depends on frequency and line length as with any other transmission line. The effects of inserting a Choke Balun between an unbalanced tuner and a balanced transmission line to the antenna can be beneficial insofar as tuner settings are concerned. But in general, the length of line on a choke balun should not exceed 1/8th or 1/10th of a wavelength at the highest frequency of use. This is not too difficult to achieve in the HF range of 1.8 or 3.5 to 30 MHz. But I do not understand what is meant by a Current Balun. Perhaps Roy, who is very good at it, could define what is a Current Balun if there is such a thing. And while he is about it, Voltage and Choke Baluns. He may choose to give them different names. But his views can only be beneficial to the mislading waffle which surounds them. ---- Reg. Article: 219511 of rec.radio.amateur.antenna From: "Fred W4JLE" References: Subject: Re: is voltage balun right choice? Date: Sat, 26 Nov 2005 16:42:59 -0500 Message-ID: No, a current balun is the desired beasty in this case. "RB" wrote in message news:sd%hf.36598$6y4.31271@bignews3.bellsouth.net... > I've recently put up a 140' dipole fed with ladderline. My tuner is > separate from my rig, and is an unbalanced unit. So, I use a balun on the > tuner output to hook the ladderline to. > > I've been told that I should have a voltage balun in this application. I > was surprised to hear this, as I expected to hear use a current balun. > > Is the voltage balun the right one for this application? > > Article: 219512 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: is voltage balun right choice? Date: Sat, 26 Nov 2005 22:55:12 +0000 (UTC) Message-ID: References: A choke (or current) balun is the correct choice. The input impedance of the transmission line to the antenna varies all over the shop from one band to another. So there is no definite impedance to which the transmitter is to be matched. A voltage balun is designed to match between two definite known impedances of a given ratio, for example 4-to-1, 300-to-75 ohms, values which never exist at your particular place in the system. A choke or current balun is not intended to match one impedance to another. It is intended only to allow, without loss, the transition >from a balanced line to an unbalanced tuner or transmitter. Because the choke balun is in fact a short length of transmission line wound on a ferrite core, an impedance transformation does occur between one end and the other. But what the antenna line input impedance is transformed to doesn't matter. It is just another impedance for the tuner to handle and, as likely as not, the tuner will handle it just as well. Just a change in L and C settings. ---- Reg, G4FGQ. Article: 219513 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: is voltage balun right choice? References: Message-ID: Date: Sat, 26 Nov 2005 23:22:51 GMT Reg Edwards wrote: > A choke or current balun is not intended to match one impedance to > another. Reg, there are 4:1 current baluns. See Figs A3-3,4 in Roy's Balun article. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219514 of rec.radio.amateur.antenna From: Cecil Moore Subject: WorldRadio Magazine Article Message-ID: Date: Sat, 26 Nov 2005 23:32:55 GMT Part 1 of my WorldRadio Oct. 2005 energy analysis article is now available on my web page in Microsoft Word .doc format. -- 73, Cecil http://www.qsl.net/w5dxp/energy.doc Article: 219515 of rec.radio.amateur.antenna Message-ID: <4lan53-g8n.ln1@mail.specsol.com> From: jimp@specsol.spam.sux.com Subject: Re: SWR again. References: Date: Sun, 27 Nov 2005 00:20:01 GMT Reg Edwards wrote: > ******* Copied from uk.radio.amateur newsgroup. ******** > > Reg spoke of the SWR meter as a resistance bridge. It is possible to > build a > > meter that is a bridge > =================================== > The so-called SWR meter is ALWAYS a resistance bridge (although it may > be described in other terms). Utter nonsense. There are numerous ways to measure SWR without using a bridge of any kind. A bridge implementation is mearly a simple and cheap way to do it and hence the most likely to be found in use by a hobbiest. -- Jim Pennino Remove .spam.sux to reply. Article: 219516 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: is voltage balun right choice? Date: Sun, 27 Nov 2005 00:34:02 +0000 (UTC) Message-ID: References: Cec, a choke balun has an indeterminate ratio. A choke balun which the man asked about, is, as you say, a current balun. I don't doubt that there are some forms of current baluns which have a definite ratio. But they have more than two wires. They can be used to transform one admittance or susceptance to another. ;o) One thing for sure - they are all transmission line transformers - for the want of a better name! In some ways they are remarkable components. They should have been invented 100 years before alongside ordinary L,C, R & G. But they had to wait for the invention of ferrites which I understand did not occur until the early 1940's in wartime Holland. But I would not be surprised if somebody comes along with the idea that the invention was in Bell Labs in the 1930's. Even before the Smith Chart which was an adaption of similar charts in use in the late Victorian Age. In the 1950's I met an American engineer who told me that in 1945 there were Americans looking round bombed-out German radio factories and by chance came across some tiny top hats with narrow brims and with 3 fine wires sticking out of one end. "What on Earth are these" they asked. I could go on. It's the Devil which makes me say such things. ;o) ---- Reg. Article: 219517 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Sun, 27 Nov 2005 01:06:23 +0000 (UTC) Message-ID: References: <4lan53-g8n.ln1@mail.specsol.com> > > > Reg spoke of the SWR meter as a resistance bridge. It is possible to > > build a > > > meter that is a bridge > > =================================== > > > The so-called SWR meter is ALWAYS a resistance bridge (although it may > > be described in other terms). > > Utter nonsense. > > There are numerous ways to measure SWR without using a bridge of any > kind. > > A bridge implementation is mearly a simple and cheap way to do it and > hence the most likely to be found in use by a hobbiest. > ===================================== I'm sorry to say you are all banging your heads against a brick wall. The so-called SWR meter does NOT measure SWR. For starters, there is no transmission line on which to measure anything. Can you find one? It is NOT the one which goes between tuner and antenna. To measure SWR on THAT line the meter has to be located in the air at the antenna end of the line and has to be read using an astronomical telescope mounted on a tripod. But it would still give the wrong answers. Go and think about it some more. ---- Reg, G4FGQ Article: 219518 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: is voltage balun right choice? Date: Sat, 26 Nov 2005 17:44:48 -0800 Message-ID: <11oi3sj7sagavf4@corp.supernews.com> References: You might find it instructive to take a look at http://eznec.com/Amateur/Articles/Baluns.pdf. Roy Lewallen, W7EL RB wrote: > I've recently put up a 140' dipole fed with ladderline. My tuner is > separate from my rig, and is an unbalanced unit. So, I use a balun on the > tuner output to hook the ladderline to. > > I've been told that I should have a voltage balun in this application. I > was surprised to hear this, as I expected to hear use a current balun. > > Is the voltage balun the right one for this application? > > Article: 219519 of rec.radio.amateur.antenna Message-ID: <40gn53-lf7.ln1@mail.specsol.com> From: jimp@specsol.spam.sux.com Subject: Re: SWR again. References: <4lan53-g8n.ln1@mail.specsol.com> Date: Sun, 27 Nov 2005 01:55:01 GMT Reg Edwards wrote: > > > > Reg spoke of the SWR meter as a resistance bridge. It is > possible to > > > build a > > > > meter that is a bridge > > > =================================== > > > > > The so-called SWR meter is ALWAYS a resistance bridge (although it > may > > > be described in other terms). > > > > Utter nonsense. > > > > There are numerous ways to measure SWR without using a bridge of any > > kind. > > > > A bridge implementation is mearly a simple and cheap way to do it > and > > hence the most likely to be found in use by a hobbiest. > > > ===================================== > I'm sorry to say you are all banging your heads against a brick wall. It feels that way when trying to discuss SWR with you. > The so-called SWR meter does NOT measure SWR. Depends on what you call a SWR meter and what you mean by measure, but this has already been hashed to bits. > For starters, there is no transmission line on which to measure > anything. Can you find one? It is NOT the one which goes between > tuner and antenna. It depends on how you implement the hardware to measure SWR, but you are so obsessed with bridge circuits you have little chance of understanding there is more in the world. What do tuners have to do with anything? Tuners are irrelevant to the original post. Are you deliberately trying to confuse the issue or do tuners confuse you? > To measure SWR on THAT line the meter has to be located in the air at > the antenna end of the line and has to be read using an astronomical > telescope mounted on a tripod. But it would still give the wrong > answers. > Go and think about it some more. I did in EE class about 30 years ago and numerous times since. Guess what, the physics hasn't changed. You are so obsessed on this issue that the small nugget of information you have to offer is swamped by the enormous amount of arm waving and babble. > ---- > Reg, G4FGQ -- Jim Pennino Remove .spam.sux to reply. Article: 219520 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Sun, 27 Nov 2005 02:59:42 +0000 (UTC) Message-ID: References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> > You are so obsessed on this issue that the small nugget of information > you have to offer is swamped by the enormous amount of arm waving > and babble. > ================================== I'm afraid your reduction to personalities is a positive indication to bystanders you have lost the argument and have accepted defeat. No hard feelings! Have a good day! ---- Reg, G4FGQ Article: 219521 of rec.radio.amateur.antenna From: "Dick, AA5VU" Subject: Got Lucky on Six meters w/Fan Dipole Message-ID: Date: Sun, 27 Nov 2005 03:06:26 GMT I picked up a new (to me) TS-570S(G) so I can start working six meters. I do not have a dedicated six meter antenna so I decided to try my Fan dipole. It was a 40/80 W9INN dipole that I modified for 18 MHz and 10 MHz by adding two sets of wires. I tried it on 50.125 and rig loves it. I can get full power with whisper of SWR that the TS-570S can easily handle. The SWR on 51 and 52 MHz is not that good; however, the auto-tuner makes the 570 smile. I am not really concerned as I plan operate mostly at 50 MHz. Something tells me the 18 MHz wires are semi-resonant at 50 MHz and I got lucky. 73, Dick AA5VU Article: 219522 of rec.radio.amateur.antenna From: Butch Magee Subject: Re: Radio Shack and my education Date: Sat, 26 Nov 2005 21:08:54 -0600 Message-ID: <11oi8q6p45q8fde@corp.supernews.com> References: <43865eea$0$32203$39cecf19@news.twtelecom.net> Whut is wrong with memorizing the test questions? I did that all through school, from pre-kindergarten to the present. Thats why I know so much stuff..........well, I sorta know a bunch of stuff. Buttt, I R Retired now and I don't have to know anything anymore. Now, aint that some shit. Ole' Butch said that.. Tom Ring wrote: > Owen Duffy wrote: > >> On 23 Nov 2005 20:29:37 GMT, Allodoxaphobia >> wrote: >> >> >> >>> Too much ruckus has been focused on the 'No Code License' issue. >>> The ruckus should, instead, be focused on the 'No Clue License'. >> >> >> >> I never mentioned the no-code licence... we got over that over a year >> ago down under. >> >> I suggest it is not a matter of the no-clue licence, but the no-clue >> licensee, who could be licensed in any grade. >> >> Owen >> (Spelling correct for country of origin!) >> -- > > > Correct. I have personally met more extras without a clue than > generals, and that's not percentage-wise. Your personal mileage may > vary, but a lot of extras seem to be really code oriented or contest > oriented, and did nothing but memorize the technical questions answers > (US) to pass. > > I do not maean to disparage anyone who got their license by legitimate > means. > > Wasn't there a scandal around that sort of thing a while ago. The name > West comes to mind, but I truthfully don't remember anything more than > that. > > tom > K0TAR Article: 219523 of rec.radio.amateur.antenna Date: Sat, 26 Nov 2005 21:14:02 -0600 From: Tom Ring Subject: Re: SWR again. References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> Message-ID: <4389248a$0$3756$39cecf19@news.twtelecom.net> Reg Edwards wrote: >>You are so obsessed on this issue that the small nugget of > > information > >>you have to offer is swamped by the enormous amount of arm waving >>and babble. >> > > ================================== > > I'm afraid your reduction to personalities is a positive indication to > bystanders you have lost the argument and have accepted defeat. > > No hard feelings! Have a good day! > ---- > Reg, G4FGQ > > Reg As someone who has watched from the sidelines for quite a while, I think you need to consult a psychiatrist, You really are obsessed over this. I am not kidding, no shit. You seem normal in most of your responses, but when it comes to SWR meters you really do seem to lose it. tom K0TAR Article: 219524 of rec.radio.amateur.antenna Date: Sat, 26 Nov 2005 21:18:21 -0600 From: Tom Ring Subject: Re: Radio Shack and my education References: <43865eea$0$32203$39cecf19@news.twtelecom.net> <11oi8q6p45q8fde@corp.supernews.com> Message-ID: <4389258d$0$3756$39cecf19@news.twtelecom.net> Well, I guess he summed it up quite succinctly. tom K0TAR Butch Magee wrote: > Whut is wrong with memorizing the test questions? I did that all > through school, from pre-kindergarten to the present. Thats why I know > so much stuff..........well, I sorta know a bunch of stuff. Buttt, I R > Retired now and I don't have to know anything anymore. Now, aint that > some shit. > Ole' Butch said that.. > > > Tom Ring wrote: > >> Owen Duffy wrote: >> >>> On 23 Nov 2005 20:29:37 GMT, Allodoxaphobia >>> wrote: >>> >>> >>> >>>> Too much ruckus has been focused on the 'No Code License' issue. >>>> The ruckus should, instead, be focused on the 'No Clue License'. >>> >>> >>> >>> >>> I never mentioned the no-code licence... we got over that over a year >>> ago down under. >>> >>> I suggest it is not a matter of the no-clue licence, but the no-clue >>> licensee, who could be licensed in any grade. >>> >>> Owen >>> (Spelling correct for country of origin!) >>> -- >> >> >> >> Correct. I have personally met more extras without a clue than >> generals, and that's not percentage-wise. Your personal mileage may >> vary, but a lot of extras seem to be really code oriented or contest >> oriented, and did nothing but memorize the technical questions answers >> (US) to pass. >> >> I do not maean to disparage anyone who got their license by legitimate >> means. >> >> Wasn't there a scandal around that sort of thing a while ago. The >> name West comes to mind, but I truthfully don't remember anything more >> than that. >> >> tom >> K0TAR Article: 219525 of rec.radio.amateur.antenna From: Butch Magee Subject: Re: WorldRadio Magazine Article Date: Sat, 26 Nov 2005 21:25:50 -0600 Message-ID: <11oi9pv3me11fe4@corp.supernews.com> References: Cecil Moore wrote: > Part 1 of my WorldRadio Oct. 2005 energy analysis article is > now available on my web page in Microsoft Word .doc format. Yo, I can''t get to you're web site. Must be because I memorized everything coming up. Yep, ats where I mussed up. Butch Article: 219526 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Got Lucky on Six meters w/Fan Dipole References: Message-ID: <2R9if.24834$q%.23288@newssvr12.news.prodigy.com> Date: Sun, 27 Nov 2005 03:36:30 GMT Dick, AA5VU wrote: > Something tells me the 18 MHz wires are semi-resonant at 50 MHz > and I got lucky. If the 40m dipole is still intact, 50/7.14 = 7 -- 73, Cecil http://www.qsl.net/w5dxp Article: 219527 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Sun, 27 Nov 2005 04:39:17 +0000 (UTC) Message-ID: References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> <4389248a$0$3756$39cecf19@news.twtelecom.net> "Tom Ring" wrote > As someone who has watched from the sidelines for quite a while, I think > you need to consult a psychiatrist, You really are obsessed over this. > I am not kidding, no shit. > > You seem normal in most of your responses, but when it comes to SWR > meters you really do seem to lose it. ---------------------------------------------------------------------- ----- Doctor Tom, Hasn't it occurred to you that if most of my responses are normal then there's no reason to suppose my response to so- called SWR meters should be otherwise. If ever I should feel the need to consult a psychiatrist then I would make arrangements to see one. I would ignore the unqualified opinions of quacks and old-wives on this newsgroup who have allowed themselves to be brainwashed just by the mis-naming of an indicating instrument. My only reason for continuing with the subject is to provide some education to novices although it seems some of the 'experts' are also in need of it. If YOU wish to continue with the subject then please say which of my very few earlier technical statements you think are incorrect, and why you think so. If the discussion should drift towards my personal character then it will be taken as an indication you have lost the argument and have nothing further to say. Otherwise go QRT ---- Reg, G4FGQ Article: 219528 of rec.radio.amateur.antenna From: "Charlie" Subject: Re: SWR again. Date: Sat, 26 Nov 2005 22:59:11 -0600 Message-ID: <11oif98lke3rk15@news.supernews.com> References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> <4389248a$0$3756$39cecf19@news.twtelecom.net> I wonder how many band openings both of you have missed while participating in this cyber pissing contest? -- Charlie "Reg Edwards" wrote in message news:dmbd9l$34e$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > > "Tom Ring" wrote >> As someone who has watched from the sidelines for quite a while, I > think >> you need to consult a psychiatrist, You really are obsessed over > this. >> I am not kidding, no shit. >> >> You seem normal in most of your responses, but when it comes to SWR >> meters you really do seem to lose it. > ---------------------------------------------------------------------- > ----- > > Doctor Tom, > > Hasn't it occurred to you that if most of my responses are normal then > there's no reason to suppose my response to so- called SWR meters > should be otherwise. > > If ever I should feel the need to consult a psychiatrist then I would > make arrangements to see one. I would ignore the unqualified opinions > of quacks and old-wives on this newsgroup who have allowed themselves > to be brainwashed just by the mis-naming of an indicating instrument. > > My only reason for continuing with the subject is to provide some > education to novices although it seems some of the 'experts' are also > in need of it. > > If YOU wish to continue with the subject then please say which of my > very few earlier technical statements you think are incorrect, and why > you think so. > > If the discussion should drift towards my personal character then it > will be taken as an indication you have lost the argument and have > nothing further to say. > > Otherwise go QRT > ---- > Reg, G4FGQ > > Article: 219529 of rec.radio.amateur.antenna From: "RB" References: <11oi3sj7sagavf4@corp.supernews.com> Subject: Re: is voltage balun right choice? Message-ID: Date: Sun, 27 Nov 2005 01:29:29 -0600 Good replies. Thanks. So: does the commonly available choke balun (round cylinder with coax connectors on each end, and ferrite beads inside the cylinder) allow us to put unbalanced feed in one end, and get balanced feed on the other? Or, are they ununs? Article: 219530 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: is voltage balun right choice? Date: Sun, 27 Nov 2005 02:55:25 -0800 Message-ID: <11oj4514qm9bne4@corp.supernews.com> References: <11oi3sj7sagavf4@corp.supernews.com> A properly operating choke (current) balun will cause the currents in the two conductors to be balanced (equal and opposite) at both ports. So I guess you could call it a balbal if you want. Why would anyone want a device that causes the currents at both ports to be unbalanced? Roy Lewallen, W7EL RB wrote: > Good replies. Thanks. > > So: does the commonly available choke balun (round cylinder with coax > connectors on each end, and ferrite beads inside the cylinder) allow us to > put unbalanced feed in one end, and get balanced feed on the other? > > Or, are they ununs? > > Article: 219531 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: is voltage balun right choice? References: <11oi3sj7sagavf4@corp.supernews.com> Message-ID: Date: Sun, 27 Nov 2005 14:59:54 GMT RB wrote: > So: does the commonly available choke balun (round cylinder with coax > connectors on each end, and ferrite beads inside the cylinder) allow us to > put unbalanced feed in one end, and get balanced feed on the other? > Or, are they ununs? Since they function by choking RF on the outside braid, they can function as either baluns or ununs. If RF is choked and not flowing on the outside braid, then differential currents are forced to flow in the two remaining conductors be they parallel wires or the inside wire and braid of the coax. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219532 of rec.radio.amateur.antenna Date: Sun, 27 Nov 2005 09:03:09 -0600 From: Tom Ring Subject: Re: SWR again. References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> <4389248a$0$3756$39cecf19@news.twtelecom.net> <11oif98lke3rk15@news.supernews.com> Message-ID: <4389cabd$0$3756$39cecf19@news.twtelecom.net> Charlie wrote: > I wonder how many band openings both of you have missed while participating > in this cyber pissing contest? > Let's see, I have made one comment on the subject of Reg and SWR measurement. Ever. So probably none. And all I said was that he seemed to be obsessive. I never said anything about the validity of his arguments, so I cerainly was not involved in a pissing contest. I think it's all quite amusing actually. tom K0TAR Article: 219533 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Station ground/2nd floor References: Message-ID: Date: Sun, 27 Nov 2005 17:27:04 GMT Mark, Sounds like a 'balanced' antenna to me, why a ground other than for electrical purposes (not RF)? - 'Doc Article: 219534 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Got Lucky on Six meters w/Fan Dipole References: <2R9if.24834$q%.23288@newssvr12.news.prodigy.com> Message-ID: Date: Sun, 27 Nov 2005 18:45:12 GMT Scott wrote: > Maybe it's warm where you are, but antenna modification season has ended > here in Wisconsin (for the most part!) Here in East Texas close to Texas A&M, the expected high is 84 degrees today with lots of sun and wind. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219535 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> Message-ID: <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> Date: Sun, 27 Nov 2005 18:49:30 GMT Mark Sheffield wrote: > I'm not quite balanced in the feed, as I'm using coax out to the > dipole feedpoint, but probably close enough. A W2DU choke would probably eliminate the need for an RF ground and also be good engineering practice. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219536 of rec.radio.amateur.antenna From: "John, N9JG" References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> Subject: Re: Station ground/2nd floor Message-ID: <_Tnif.606420$xm3.396820@attbi_s21> Date: Sun, 27 Nov 2005 19:35:22 GMT I have a 2nd floor shack too, and the antenna is a ground mounted vertical (Butternut HF6V). I use a W2DU choke to connect my coax feedline to the vertical and a 2nd W2DU choke between my Orion and Drake L-4B. Finally, I found that the only way to prevent feedback on SSB was to NOT connect my system to the #8 ground wire that runs out the window sill and down to a ground rod. "Cecil Moore" wrote in message news:_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com... > Mark Sheffield wrote: >> I'm not quite balanced in the feed, as I'm using coax out to the >> dipole feedpoint, but probably close enough. > > A W2DU choke would probably eliminate the need for > an RF ground and also be good engineering practice. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 219537 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <11oi3sj7sagavf4@corp.supernews.com> Subject: Re: is voltage balun right choice? Date: Sun, 27 Nov 2005 14:50:26 -0500 Message-ID: A choke balun allows you to go from unbalanced to balanced. If you check Walter Maxwells site and review Chapter 21 (IIRC) of reflections. He gives a test setup that will aid in understanding. "RB" wrote in message news:Tddif.89036$ty1.39736@bignews1.bellsouth.net... > Good replies. Thanks. > > So: does the commonly available choke balun (round cylinder with coax > connectors on each end, and ferrite beads inside the cylinder) allow us to > put unbalanced feed in one end, and get balanced feed on the other? > > Or, are they ununs? > > Article: 219538 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> Message-ID: Date: Sun, 27 Nov 2005 20:03:27 GMT John, N9JG wrote: > Finally, I > found that the only way to prevent feedback on SSB was to NOT connect my > system to the #8 ground wire that runs out the window sill and down to a > ground rod. Yep, everyone should realize that a ground wire is N*1/4 wavelength at certain frequencies, and at those frequencies, is an RF transformer that locates the standing-wave voltage maximum points at the transmitter. (ouch!) That's what artificial grounds do - change that *electrical* length to N*1/2 wavelength. For anyone insisting on an RF ground for an upper floor, an artificial ground is probably the way to go. I, myself, prefer balanced antennas and feedlines. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219539 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <2R9if.24834$q%.23288@newssvr12.news.prodigy.com> Subject: Re: Got Lucky on Six meters w/Fan Dipole Date: Sun, 27 Nov 2005 15:21:39 -0500 Message-ID: <70f23$438a1555$97d56a33$23027@ALLTEL.NET> We are having a real cold snap here in South Carolina, it only reached 73 today. "Cecil Moore" wrote in message news:Y8nif.19155$BZ5.18183@newssvr13.news.prodigy.com... > Scott wrote: > > Maybe it's warm where you are, but antenna modification season has ended > > here in Wisconsin (for the most part!) > > Here in East Texas close to Texas A&M, the expected high > is 84 degrees today with lots of sun and wind. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 219540 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1133101079.399556.132760@z14g2000cwz.googlegroups.com> Subject: Re: Source for good trap boots for tri-bander??? Date: Sun, 27 Nov 2005 15:23:52 -0500 Message-ID: <4464e$438a15da$97d56a33$23125@ALLTEL.NET> Check with your local motorcycle shop. They have boots for the the front shock absorbers that I have used in the past. "Dave - KB8NNU" wrote in message news:1133101079.399556.132760@z14g2000cwz.googlegroups.com... > Howdy all....I am in the process of rebuilding an older tribander that > I have and need some input. I want to replace all of the trap boots, > but don't know where to get such a thing. I'm not sure what kind of > antenna it is. I originally thought it was a TA-33 jr...??? The traps > have a diameter of 1.5'' and the anntenna diameter is .75''. Any help > would greatly be appreciated. > > Thanks, > > Dave - KB8NNU > Article: 219541 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Sun, 27 Nov 2005 20:27:48 +0000 (UTC) Message-ID: References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> <4389248a$0$3756$39cecf19@news.twtelecom.net> <11oif98lke3rk15@news.supernews.com> <4389cabd$0$3756$39cecf19@news.twtelecom.net> > I think it's all quite amusing actually. > > tom > K0TAR =================================== So do I. ---- Reg, G4FGQ Article: 219542 of rec.radio.amateur.antenna From: "Jerry" References: <2R9if.24834$q%.23288@newssvr12.news.prodigy.com> Subject: Re: Got Lucky on Six meters w/Fan Dipole Message-ID: Date: Sun, 27 Nov 2005 16:13:28 -0500 "Cecil Moore" wrote in message news:Y8nif.19155$BZ5.18183@newssvr13.news.prodigy.com... > Scott wrote: >> Maybe it's warm where you are, but antenna modification season has ended >> here in Wisconsin (for the most part!) > > Here in East Texas close to Texas A&M, the expected high > is 84 degrees today with lots of sun and wind. > -- > 73, Cecil http://www.qsl.net/w5dxp Ya like to rub it in, eh? ;) Jerry (Here, 40's with a chilly rain. :( ) Article: 219543 of rec.radio.amateur.antenna From: Korbin Dallas Subject: Re: Radio Shack and my education Message-ID: References: <43866294$0$3756$39cecf19@news.twtelecom.net> Date: Sun, 27 Nov 2005 21:30:34 GMT On Thu, 24 Nov 2005 19:01:57 -0600, Tom Ring wrote: > And from what I've seen, nothing has changed, Bose is still selling > millions of dollars of crap. > > tom > K0TAR Man ain't that the truth. I have never understood this Bose thing, the speakers are some of the worst ones on the market and they are flying out the doors all day long. Its all marketing BS like the Wizbang cables to hook things up. -- Korbin Dallas The name was changed to protect the guilty. Article: 219544 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <43866294$0$3756$39cecf19@news.twtelecom.net> Message-ID: <43qif.25182$Zv5.24376@newssvr25.news.prodigy.net> Date: Sun, 27 Nov 2005 22:03:44 GMT Korbin Dallas wrote: > I have never understood this Bose thing, the speakers are some of the > worst ones on the market and they are flying out the doors all day long. > Its all marketing BS like the Wizbang cables to hook things up. Sharper Image does the same thing. Their room air filter has got to be close to the worst-case design I have ever seen. The guy in their commercial who says, "I have tried every air purifier on the market and ..." is an UNETHICAL LYING SOB!!!! 'Course, most TV commercials are made by unethical liars. I doubt that many of the alleged cancer sufferers actually have cancer. They look more like professional models to me. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219545 of rec.radio.amateur.antenna From: Wayne Watson Subject: Antennas-History (What's Going On?) Message-ID: Date: Sun, 27 Nov 2005 22:05:08 GMT I hardly know where to start with this topic. If one picks up some of the fairly popular (available?) books on the matter, the authors invariably start throwing different types of antennas at the reader, yagi, helical, dipole, folded dipole, parabolic, loop, dish, microwave, quads, etc. For example, I'm looking at an older book on the topic I bought some 20 years ago, The Radio Amateur Handbook by Orr and Cowan. The book is basically for builders. Many such books are. What about the underlying methodology behind this? More generally, here's my question. I would guess that in the beginning (late 1800s) the simple dipole was it. As years passed, the complexity of antennas has increased. What was the driving force for these changes? For example, how did the inventor of the Yagi (Yagi-Uda) ever dream up the idea for the antenna? Was it the application of theory or did he just get lucky? In fact, is there some underlying theory that drives the design of antennas? For example, the computation of radiation patterns. I'm sure these days the computer would be an aid, but what theory and application drove the development of varied designs before 1960? When did Maxwell's equations seriously get used for this? What suggested a tin can could become an antenna? How did anyone think up the idea of a microwave antenna? I would think that in the case of antennas that are used for different parts of the EM spectrum a driving force would be the consideration of the wave itself. For example, it would seem unlikely an x-ray antenna (I believe there is such a thing on one of the space satellites used in astronomy) would be anything like one used to receive TV. Certainly the 'antenna' to collect visible light is different than that for AM radio. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219546 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antennas-History (What's Going On?) References: Message-ID: Date: Sun, 27 Nov 2005 22:13:42 GMT Wayne Watson wrote: > For example, it would seem unlikely an x-ray antenna (I believe > there is such a thing on one of the space satellites used in astronomy) > would be anything like one used to receive TV. Certainly the 'antenna' to > collect visible light is different than that for AM radio. Is it easier to pick up a twig than to pick up a tree? Methinks you need a better understanding of wavelength. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219547 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <43866294$0$3756$39cecf19@news.twtelecom.net> <43qif.25182$Zv5.24376@newssvr25.news.prodigy.net> Subject: Re: Radio Shack and my education Date: Sun, 27 Nov 2005 17:18:21 -0500 Message-ID: Come on Cecil, next you will be telling me there is no Santa Clause... "Cecil Moore" wrote in message news:43qif.25182$Zv5.24376@newssvr25.news.prodigy.net... > Korbin Dallas wrote: > > I have never understood this Bose thing, the speakers are some of the > > worst ones on the market and they are flying out the doors all day long. > > Its all marketing BS like the Wizbang cables to hook things up. > > Sharper Image does the same thing. Their room air filter has got > to be close to the worst-case design I have ever seen. The guy > in their commercial who says, "I have tried every air purifier > on the market and ..." is an UNETHICAL LYING SOB!!!! 'Course, most > TV commercials are made by unethical liars. I doubt that many > of the alleged cancer sufferers actually have cancer. They look > more like professional models to me. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 219548 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> <1133129531.934671.87410@o13g2000cwo.googlegroups.com> Message-ID: Date: Sun, 27 Nov 2005 22:21:45 GMT jgboyles@aol.com wrote: > Cecil, Don't you mean that when a ground wire is N*1/4 wavelength at > a particular frequency it locates the voltage mininum (current maximum) > at the transmitter, and the voltage maximum well away from the > transmitter. Nope, Mother Earth dictates the boundary conditions. A well-designed ground system positions the current maximum point at the ground system, i.e. minimum impedance to ground. The voltage maximum point would, therefore, be located at the transmitter, not a desirable condition. Of course, if you are not actually connected/ coupled to Mother Earth, your milage may vary. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219549 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Radio Shack and my education References: <43866294$0$3756$39cecf19@news.twtelecom.net> <43qif.25182$Zv5.24376@newssvr25.news.prodigy.net> Message-ID: <8qqif.25193$Zv5.10176@newssvr25.news.prodigy.net> Date: Sun, 27 Nov 2005 22:28:20 GMT Fred W4JLE wrote: > Come on Cecil, next you will be telling me there is no Santa Clause... It's hard to argue that there's no Santa Claus when one can observe a real live Santa Claus in every mall. What's seems harder to argue is the existence of a God whom nobody alive has ever sensed with any of their allegedly God-given senses. :-) (The Devil made me say that.) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219550 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> <438A3123.AC0E860D@shaw.ca> Message-ID: Date: Sun, 27 Nov 2005 22:35:26 GMT Irv Finkleman wrote: > Why not run two ground wires in parallel -- one twice as long as the > other? When one is Hi-Z the other will be Lo-Z and vice versa. That will help on some frequencies but it is akin to trying to erect a 1/2WL fan dipole for all frequencies - can't be done. Sooner or later, you will run into a frequency where length #1 is N*1/4WL and length #2 is (N+1)1/4WL. "It's not nice to fool Mother Nature." -- 73, Cecil http://www.qsl.net/w5dxp Article: 219551 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> <1133129531.934671.87410@o13g2000cwo.googlegroups.com> <1133131540.142286.97990@f14g2000cwb.googlegroups.com> Message-ID: Date: Sun, 27 Nov 2005 22:57:12 GMT jgboyles@aol.com wrote: > That is where an artifical ground can help by locating > the voltage minimum at the transmitter. Yes, that's true. An artifical ground equalizes the voltage at the ground point AND at the transmitter so both are voltage minimum (current maximum) points. That's exactly what an antenna tuner does when feeding a resonant 1/2WL dipole fed with ladder-line through an antenna tuner. I hope I didn't misunderstand what you were trying to say. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219552 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: Antennas-History (What's Going On?) References: Message-ID: Date: Sun, 27 Nov 2005 23:01:51 GMT Cecil Moore wrote: > Wayne Watson wrote: > >> For example, it would seem unlikely an x-ray antenna (I believe >> there is such a thing on one of the space satellites used in astronomy) >> would be anything like one used to receive TV. Certainly the 'antenna' to >> collect visible light is different than that for AM radio. > > > Is it easier to pick up a twig than to pick up a tree? > Methinks you need a better understanding of wavelength. Why not provide it then? -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219553 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antennas-History (What's Going On?) Date: Sun, 27 Nov 2005 15:20:20 -0800 Message-ID: <11okfpommc4nd0b@corp.supernews.com> References: Wayne Watson wrote: > I hardly know where to start with this topic. If one picks up some of > the fairly popular (available?) books on the matter, the authors > invariably start throwing different types of antennas at the reader, > yagi, helical, dipole, folded dipole, parabolic, loop, dish, > microwave, quads, etc. For example, I'm looking at an older book on > the topic I bought some 20 years ago, The Radio Amateur Handbook by > Orr and Cowan. The book is basically for builders. Many such books > are. What about the underlying methodology behind this? More > generally, here's my question. > > I would guess that in the beginning (late 1800s) the simple dipole > was it. As years passed, the complexity of antennas has increased. > What was the driving force for these changes? Since the beginning of radio, antenna design has been driven mostly by specific needs, to name just a very few examples: -- By broadcasters to increase their coverage areas -- By military users: to increase portability and range to decrease detectable emissions in some directions to allow broadband performance for frequency hopping -- By satellite system designers to concentrate limited energy in particular regions. -- By cell phone companies to provide coverage to well-defined regions The list is endless. Take a trip to your local library and get an index to the I.R.E. (now the IEEE) Transactions on Antennas and Propagation. You'll see that many advances were made in the '20s and '30s in AM broadcast antennas, in the '40s and '50s in aircraft antennas, in the '60s and '70s in satellite antennas. Much of today's development work involves compact antennas for the wireless networks now proliferating. Antennas provide a limitless pool of tradeoffs involving size, cost, ruggedness, and a large handful of performance characteristics such as directionality, gain, and bandwidth. This pretty much guarantees that new designs will continue to be created. > For example, how did the inventor of the Yagi (Yagi-Uda) ever dream > up the idea for the antenna? Was it the application of theory or did > he just get lucky? How is any creative design accomplished? How did Armstrong come up with the idea for FM, Watt for the steam engine? I've spent most of my career doing circuit design, and it requires a deep knowledge of theory, but also involves a creative synthesis not unlike what an artist has in deciding what to paint or an architect in deciding what form a building will take. > In fact, is there some underlying theory that drives the design of > antennas? For example, the computation of radiation patterns. You're confusing design and analysis. Design is driven primarily by a need for a particular set of performance parameters. Analysis is done by computation. Analysis is an important part of the design process, in that a design, once created, is analyzed to see if and how well it meets design goals. The design is then often modified and re-analyzed many times until the goal is reached, the design abandoned, or the goal redefined. And yes, indeed, there's solid theory underlying antenna operation. > I'm sure these days the computer would be an aid, but what theory and > application drove the development of varied designs before 1960? Hopefully what I've said above has answered this. A lot more physical modeling and experimentation were required before computers were available, but design was still driven by need, and theory hasn't changed significantly for many decades. There's no magic computer program that you can put some numbers into and out comes the optimum aircraft design, or bridge, or car, or house. Antennas are no different. Computers can be used to optimize a particular class of antenna (e.g., Yagi or patch) for a particular set of performance criteria, just as they can be used to fine-tune an aircraft or bridge once the basic structure is designed. But not to design an antenna from nothing. > When did Maxwell's equations seriously get used for this? They were used long ago as the basis of equations more directly applicable to antenna analysis, and those equations are still used by modern computer programs. In that sense, Maxwell's equations are still being used, although not directly. > What suggested a tin can could become an antenna? It's obvious to anyone who understands the most basic of principles. Any conductor can act as an antenna. A tin can is a conductor. > How did anyone think up the idea of a microwave antenna? Actually, some of the first experiments with radio waves by Heinrich Hertz were done in the microwave region, so some of the very first antennas were microwave antennas. As for modern microwave antennas, once you have microwave energy (which first became available at high power levels with the invention of the cavity magnetron in 1940), the need for an antenna becomes obvious. > I would think that in the case of antennas that are used for > different parts of the EM spectrum a driving force would be the > consideration of the wave itself. For example, it would seem unlikely > an x-ray antenna (I believe there is such a thing on one of the > space satellites used in astronomy) would be anything like one used > to receive TV. Certainly the 'antenna' to collect visible light is > different than that for AM radio. All antennas obey the same fundamental physical laws. But you're correct that the wavelength of the signal to be transmitted or received plays a big role in determining which antenna designs are practical and optimum. That's just one of the many factors that have to be considered when designing an antenna. All bridges obey the same physical laws, but the optimum design for a bridge crossing a creek is quite different from one crossing the Golden Gate. In fact, if you change "antenna" to "bridge" in your questions, you'll probably find most of the answers to be pretty obvious. Roy Lewallen, W7EL Article: 219554 of rec.radio.amateur.antenna From: "Dick, AA5VU" Subject: Re: Got Lucky on Six meters w/Fan Dipole References: <2R9if.24834$q%.23288@newssvr12.news.prodigy.com> Message-ID: Date: Sun, 27 Nov 2005 23:47:54 GMT In article , Cecil Moore wrote: > > Maybe it's warm where you are, but antenna modification season has ended > > here in Wisconsin (for the most part!) > > Here in East Texas close to Texas A&M, the expected high > is 84 degrees today with lots of sun and wind. Winter was cancelled in 2004 due to lack of participation and I think we are in for the same this year. Like Cecil, the high in the Capital was about 86 yesterday. Article: 219555 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antennas-History (What's Going On?) References: Message-ID: <_Grif.19209$BZ5.11403@newssvr13.news.prodigy.com> Date: Sun, 27 Nov 2005 23:54:34 GMT W. Watson wrote: > W. Watson wrote: >>> Wayne Watson wrote: > Let me try to make it easier on you. Are you bipolar? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219556 of rec.radio.amateur.antenna Message-ID: <438A539F.B05A771D@shaw.ca> From: Irv Finkleman Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> <438A3123.AC0E860D@shaw.ca> Date: Mon, 28 Nov 2005 00:47:26 GMT Cecil Moore wrote: > > Irv Finkleman wrote: > > Why not run two ground wires in parallel -- one twice as long as the > > other? When one is Hi-Z the other will be Lo-Z and vice versa. > > That will help on some frequencies but it is akin to trying to > erect a 1/2WL fan dipole for all frequencies - can't be done. Sooner > or later, you will run into a frequency where length #1 is N*1/4WL > and length #2 is (N+1)1/4WL. "It's not nice to fool Mother Nature." > -- > 73, Cecil http://www.qsl.net/w5dxp OK then, I'll use 3 wires and take my chances! :-) Irv -- -------------------------------------- Diagnosed Type II Diabetes March 5 2001 Beating it with diet and exercise! 297/215/210 (to be revised lower) 58"/43"(!)/44" (already lower too!) -------------------------------------- Visit my HomePage at http://members.shaw.ca/finkirv/index.html Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm -------------------- Irv Finkleman, Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP Calgary, Alberta, Canada Article: 219557 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: SWR again. References: <4lan53-g8n.ln1@mail.specsol.com> <40gn53-lf7.ln1@mail.specsol.com> <4389248a$0$3756$39cecf19@news.twtelecom.net> <11oif98lke3rk15@news.supernews.com> <4389cabd$0$3756$39cecf19@news.twtelecom.net> Message-ID: Date: Mon, 28 Nov 2005 02:02:13 GMT Reg Edwards wrote: >>I think it's all quite amusing actually. >> >>tom >>K0TAR > > =================================== > > So do I. > ---- > Reg, G4FGQ > > It ceased to be amusing 500 posts ago, but Reg has a point, however strained. 73, Tom Donaly, KA6RUH Article: 219558 of rec.radio.amateur.antenna From: "W4WNT" References: <1133023175.424981.104610@g43g2000cwa.googlegroups.com> Subject: Re: 30/20 vertical? Message-ID: Date: Mon, 28 Nov 2005 02:02:58 GMT You did not say what your vertical radiator material is. Make it out of wire (support it with PVC tubing), then you can put up 2 vertical radiators, one for 20m, the other for 30m fed by the same coax. I guess this would be a "Fan Vertical". Its based on a W6SAI design published in 1990. I've done it with 10/15/20m radiators and it works well with elevated radials made >from TV rotator wire. Good luck, Bill, W4WNT wrote in message news:1133023175.424981.104610@g43g2000cwa.googlegroups.com... > Hi, > > For 20m I am planning a quarter wavelength vertical radiator with 4 > eighth wavelength radials, mounted 12 feet high. > > If I add another 4 radials cut an eight wavelength for 30m, will it be > easier to operate on 30? > > Thanks, > > The Eternal Squire > Article: 219559 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <43866294$0$3756$39cecf19@news.twtelecom.net> <43qif.25182$Zv5.24376@newssvr25.news.prodigy.net> <8qqif.25193$Zv5.10176@newssvr25.news.prodigy.net> Subject: Re: Radio Shack and my education Date: Sun, 27 Nov 2005 22:56:42 -0500 Message-ID: <3f67$438a7ffd$97d56a33$32124@ALLTEL.NET> He has been sensed by the heart when a child is delivered from an illness, a mother gives birth to a newborn child, and in the smile of someone you have given a kindness. Just remember, he will always believe in you... "Cecil Moore" wrote in message news:8qqif.25193$Zv5.10176@newssvr25.news.prodigy.net... > Fred W4JLE wrote: > > Come on Cecil, next you will be telling me there is no Santa Clause... > > It's hard to argue that there's no Santa Claus when one can > observe a real live Santa Claus in every mall. What's seems > harder to argue is the existence of a God whom nobody alive > has ever sensed with any of their allegedly God-given senses. > :-) (The Devil made me say that.) > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 219560 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: Antennas-History (What's Going On?) References: <11okfpommc4nd0b@corp.supernews.com> Message-ID: <%nCif.2054$Hk1.1653@newsread1.news.pas.earthlink.net> Date: Mon, 28 Nov 2005 12:05:15 GMT Roy Lewallen wrote: > Wayne Watson wrote: > >> I hardly know where to start with this topic. If one picks up some of >> the fairly popular (available?) books on the matter, the authors >> invariably start throwing different types of antennas at the reader, >> yagi, helical, dipole, folded dipole, parabolic, loop, dish, >> microwave, quads, etc. For example, I'm looking at an older book on >> the topic I bought some 20 years ago, The Radio Amateur Handbook by >> Orr and Cowan. The book is basically for builders. Many such books >> are. What about the underlying methodology behind this? More >> generally, here's my question. >> >> I would guess that in the beginning (late 1800s) the simple dipole was >> it. As years passed, the complexity of antennas has increased. What >> was the driving force for these changes? > > > > Since the beginning of radio, antenna design has been driven mostly by > specific needs, to name just a very few examples: > > -- By broadcasters to increase their coverage areas > -- By military users: > to increase portability and range > to decrease detectable emissions in some directions > to allow broadband performance for frequency hopping > -- By satellite system designers to concentrate limited energy in > particular regions. > -- By cell phone companies to provide coverage to well-defined regions > > The list is endless. > > Take a trip to your local library and get an index to the I.R.E. (now > the IEEE) Transactions on Antennas and Propagation. You'll see that many > advances were made in the '20s and '30s in AM broadcast antennas, in the > '40s and '50s in aircraft antennas, in the '60s and '70s in satellite > antennas. Much of today's development work involves compact antennas for > the wireless networks now proliferating. > > Antennas provide a limitless pool of tradeoffs involving size, cost, > ruggedness, and a large handful of performance characteristics such as > directionality, gain, and bandwidth. This pretty much guarantees that > new designs will continue to be created. > >> For example, how did the inventor of the Yagi (Yagi-Uda) ever dream up >> the idea for the antenna? Was it the application of theory or did he >> just get lucky? > > > How is any creative design accomplished? How did Armstrong come up with > the idea for FM, Watt for the steam engine? I've spent most of my career > doing circuit design, and it requires a deep knowledge of theory, but > also involves a creative synthesis not unlike what an artist has in > deciding what to paint or an architect in deciding what form a building > will take. > >> In fact, is there some underlying theory that drives the design of >> antennas? For example, the computation of radiation patterns. > > > You're confusing design and analysis. Design is driven primarily by a > need for a particular set of performance parameters. Analysis is done by > computation. Analysis is an important part of the design process, in > that a design, once created, is analyzed to see if and how well it meets > design goals. The design is then often modified and re-analyzed many > times until the goal is reached, the design abandoned, or the goal > redefined. And yes, indeed, there's solid theory underlying antenna > operation. > >> I'm sure these days the computer would be an aid, but what theory and >> application drove the development of varied designs before 1960? > > > Hopefully what I've said above has answered this. A lot more physical > modeling and experimentation were required before computers were > available, but design was still driven by need, and theory hasn't > changed significantly for many decades. > > There's no magic computer program that you can put some numbers into and > out comes the optimum aircraft design, or bridge, or car, or house. > Antennas are no different. Computers can be used to optimize a > particular class of antenna (e.g., Yagi or patch) for a particular set > of performance criteria, just as they can be used to fine-tune an > aircraft or bridge once the basic structure is designed. But not to > design an antenna from nothing. > >> When did Maxwell's equations seriously get used for this? > > > They were used long ago as the basis of equations more directly > applicable to antenna analysis, and those equations are still used by > modern computer programs. In that sense, Maxwell's equations are still > being used, although not directly. > >> What suggested a tin can could become an antenna? > > > It's obvious to anyone who understands the most basic of principles. Any > conductor can act as an antenna. A tin can is a conductor. > >> How did anyone think up the idea of a microwave antenna? > > > Actually, some of the first experiments with radio waves by Heinrich > Hertz were done in the microwave region, so some of the very first > antennas were microwave antennas. As for modern microwave antennas, once > you have microwave energy (which first became available at high power > levels with the invention of the cavity magnetron in 1940), the > need for an antenna becomes obvious. > >> I would think that in the case of antennas that are used for different >> parts of the EM spectrum a driving force would be the consideration of >> the wave itself. For example, it would seem unlikely >> an x-ray antenna (I believe there is such a thing on one of the space >> satellites used in astronomy) would be anything like one used to >> receive TV. Certainly the 'antenna' to collect visible light is >> different than that for AM radio. > > > All antennas obey the same fundamental physical laws. But you're correct > that the wavelength of the signal to be transmitted or > received plays a big role in determining which antenna designs are > practical and optimum. That's just one of the many factors that have to > be considered when designing an antenna. All bridges obey the same > physical laws, but the optimum design for a bridge crossing a creek is > quite different from one crossing the Golden Gate. > > In fact, if you change "antenna" to "bridge" in your questions, you'll > probably find most of the answers to be pretty obvious. > > Roy Lewallen, W7EL Thanks. Well said. Makes sense to me. I have a very modest understanding of how antennas work, but from my simplistic view I just find it a bit odd that if one thinks of an EM wave shape and content (electric and magnetic) to all sorts of radiation that to observe much of this radiation different devices are required. From my underdeveloped perspective, I'd probably trying to design everything with some wild combinations of dipoles. Maybe I'm thinking of (hoping for) some grand unified radio or telescope (and methodology) that sucks up any EM wave one can throw at it. One size fits all. Apparently, we've got a long way to go on that. :-) -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219561 of rec.radio.amateur.antenna From: K7JEB Subject: Re: Antennas-History (What's Going On?) Message-ID: References: <11okfpommc4nd0b@corp.supernews.com> <%nCif.2054$Hk1.1653@newsread1.news.pas.earthlink.net> Date: Mon, 28 Nov 2005 07:20:05 -0700 On Mon, 28 Nov 2005 12:05:15 GMT, "W. Watson" wrote: > ...Maybe I'm thinking of (hoping for) some grand > unified radio or telescope (and methodology) that > sucks up any EM wave one can throw at it. One size > fits all. Apparently, we've got a long way to go > on that. :-) The methodology (and perhaps the viewpoint) you are looking for is... Optics. >From an Optics viewpoint, you're born with two antennas in your head (that you are using to read this). >From an Optics viewpoint, a hole in a piece of cardboard is an antenna (an aperture). >From an Optics viewpoint, radio antennas (monopoles, dipoles, yagis, Sterba curtains) are just minor peculiarities one encounters when wavelength becomes "human-sized". >From an Optics viewpoint, we've been at this for an awfully long time. Maxwell's equations and quantum mechanics are just frosting on a very large cake. A great deal of Physics has been devoted to studying electromagnetic radiation over the centuries. Unfortunately, the study of Optics is not for the faint of heart. It leads directly into the heart of the Physical Universe and things tend to get very messy, and very mathematical. However, even from the periphery, the insights are rewarding. Every time you pick up a camera, you think "antenna". Every time you see an incandescent lamp, you think "antennas" (jillions of them). Every time you see a satellite dish, you think "telescope". And so on... Jim, K7JEB Article: 219562 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Mon, 28 Nov 2005 14:33:31 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> "Saandy wrote > you can't measure SWR. ========================================= I am pleased you agree with me. ========================================= > You can CALCULATE the SWR using the formula. ========================================= But of what use is the SWR it after you have calculated it? To what transmission line does it apply? Where is it? What are the locations of max-volts and min-volts? It does NOT apply to the line between transmitter and antenna. I suggest it exists only in your imagination. ;o) It is the name of "SWR Meter" which leads to confusion, misunderstandings and arguments. The name says the instrument does something which it does not do. With the help of old-wives, novices are led astray and are stuck with incorrect ideas about standing-waves for the rest of the lives. Just change the name to TLI (Transmitter Loading Indicator) which is what it is and does very well. The true meaning and associations of SWR will then emerge and all will be flooded with the light of reason. ---- Reg, G4FGQ. Article: 219563 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antennas-History (What's Going On?) References: <11okfpommc4nd0b@corp.supernews.com> <%nCif.2054$Hk1.1653@newsread1.news.pas.earthlink.net> Message-ID: Date: Mon, 28 Nov 2005 15:20:15 GMT K7JEB wrote: > From an Optics viewpoint, we've been at this for an > awfully long time. Maxwell's equations and quantum > mechanics are just frosting on a very large cake. A > great deal of Physics has been devoted to studying > electromagnetic radiation over the centuries. In particular: An understanding of how RF reflections can be eliminated by a 1/4WL series matching section can be had from understanding how a 1/4WL layer of thin-film on glass can eliminate coherent light reflections from the surface of the thin-film. The irradiance equations which predict the power distribution of light waves undergoing interference can be used to understand RF energy flow in a transmission line with reflections. Staring at oneself in a mirror should convince any skeptical RF engineer that reflected energy actually makes a round trip to the reflection point and back and doesn't flow directly from the image-source to the eye (or to the circulator load resistor). :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219564 of rec.radio.amateur.antenna From: dt@dt.prohosting.com (David B. Thomas) Subject: Re: vert dipole vs vert Date: 28 Nov 2005 09:31:35 -0700 Message-ID: References: >>>>> "ml" == ml writes: ml> i was trying to figure loosly in real world case what the ml> difference would be (generally speaking) between say a ml> verticle all band commercial antenna on my roof (of my tall ml> apt building) i'd naturally install it's radial kit ml> vs ml> a equal all band (yeah i know it'd be tall) virticle dipole ml> (tweeked w/a tuner sgc at feedpoint The commercial vertical probably uses traps or other means to act like a quarter wave ground plane on all bands. This would be roughly equivalent, performance-wise, to a separate vertical dipole cut for each band. The issue with using the tuner is that a tall dipole used on a high frequency will throw a lot of energy up at high angles. On 15 and 10 meters, you'd probably rather have a nice low angle pattern. Then again, when those bands are open, you can usually afford to have an inefficient antenna as propagation tends to be excellent. So, if you're looking to put up something fast and cheap, the dipole and tuner idea can certainly work. If you do that, try to keep the feed line perpendicular as long as you can before it drops down. David N5IZU -- M.C. Escher had to walk to school, uphill both ways. Article: 219565 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antennas-History (What's Going On?) Date: Mon, 28 Nov 2005 10:55:40 -0600 Message-ID: <7955-438B368C-194@storefull-3256.bay.webtv.net> References: Wayne Watson wrote: "What about the underlying methodology behind this?" Please refer to the 3rd. edition of "Antennas for All Applications", by John D. Kraus with a host of other professors, for answers to nearly all your questions. Kraus organizes antennas by types. The dipole is the simplest complete antenna. But, the first practical antenna was patented by Marconi. He was interested in communications over the ocean, so only 1/2 of a dipole is needed. The return circuit is provided by the ocean. Sea water is nearly lossless. Marconi imagined the antenna as a capacitor plate.. Then he discovered the antenna worked about as well with just the connectng wires inplace, without the plate. As the 19th century turned into the 20th century, Marconi spanned the Atlantic with signals from his antennas. Best regards, Richard Harrison, KB5WZI Article: 219566 of rec.radio.amateur.antenna From: "Christopher O'Callaghan" Subject: Send spam this way Date: Mon, 28 Nov 2005 17:36:02 -0000 Message-ID: sallowswayne@aol.com send all the spam you want to this address..I can then forward this to piss of my enemy..... Article: 219567 of rec.radio.amateur.antenna From: "Caveat Lector" References: Subject: Re: Antennas-History (What's Going On?) Message-ID: Date: Mon, 28 Nov 2005 09:50:10 -0800 I think many antenna designs arose as a matter of "necessity is the mother of invention" For example here is a Yagi antenna quote from URL: http://ieee.cincinnati.fuse.net/newsletters/200405.pdf At Tohoku, Yagi initiated a research program in radio-electronics drawing on what he had learned from Barkhausen, Fleming, and Pierce. Other members of the faculty and advanced students, including Okabe and Shintaro Uda, became participants in a collective research effort. A perceived need for better communication between islands and with ships led them to focus on short wave communication with directive antennas. The Yagi group received financial support for the research from a private foundation in Sendai. In February 1926, Yagi and Uda published their first report on the wave projector antenna in a Japanese publication. For the Cubical Quad see URL: http://www.antennex.com/preview/Jan501/quad1.htm Clarence Moore, the station engineer at HCJB in Quito, and some colleagues took along with them a stack of antenna and engineering texts and a Bible on a Sabbatical in 1942. Their urgent goal was to come up with an antenna that wouldn't consume itself by corona discharge when fed with high power, as was happening to their Yagi, at the high Andean altitude of their station. A full wave loop solved the problem. Some remarkable antenna designs today because of the need to fit an antenna on a cell phone. For direction finding, loops, interferometers, etc were needed ETC -- CL -- I doubt, therefore I might be ! "Wayne Watson" wrote in message news:o4qif.1890$Hk1.1683@newsread1.news.pas.earthlink.net... >I hardly know where to start with this topic. If one picks up some of the > fairly popular (available?) books on the matter, the authors invariably > start throwing different types of antennas at the reader, yagi, helical, > dipole, folded dipole, parabolic, loop, dish, microwave, quads, etc. For > example, I'm looking at an older book on the topic I bought some 20 years > ago, The Radio Amateur Handbook by Orr and Cowan. The book is basically > for > builders. Many such books are. What about the underlying methodology > behind > this? More generally, here's my question. > > I would guess that in the beginning (late 1800s) the simple dipole was it. > As years passed, the complexity of antennas has increased. What was the > driving force for these changes? For example, how did the inventor of the > Yagi (Yagi-Uda) ever dream up the idea for the antenna? Was it the > application of theory or did he just get lucky? In fact, is there some > underlying theory that drives the design of antennas? For example, the > computation of radiation patterns. I'm sure these days the computer would > be > an aid, but what theory and application drove the development of varied > designs before 1960? When did Maxwell's equations seriously get used for > this? What suggested a tin can could become an antenna? How did anyone > think > up the idea of a microwave antenna? > > I would think that in the case of antennas that are used for different > parts > of the EM spectrum a driving force would be the consideration of the wave > itself. For example, it would seem unlikely an x-ray antenna (I believe > there is such a thing on one of the space satellites used in astronomy) > would be anything like one used to receive TV. Certainly the 'antenna' to > collect visible light is different than that for AM radio. > > -- > Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) > (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) > Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet > > Traveling in remote places in the winter. What's the best > tool to carry with you? An axe. > -- Survivorman, Discovery (SCI) Channel > > Web Page: > > > Article: 219568 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Subject: Re: SWR again. Message-ID: Date: Mon, 28 Nov 2005 17:54:35 GMT "Reg Edwards" wrote in message news:dmf4fr$4cu$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > > "Saandy wrote > >> you can't measure SWR. > ========================================= > > I am pleased you agree with me. > > ========================================= >> You can CALCULATE the SWR using the formula. > ========================================= > > But of what use is the SWR it after you have calculated it? > > To what transmission line does it apply? Where is it? What are the > locations of max-volts and min-volts? It does NOT apply to the line > between transmitter and antenna. I suggest it exists only in your > imagination. ;o) > > It is the name of "SWR Meter" which leads to confusion, > misunderstandings and arguments. The name says the instrument does > something which it does not do. With the help of old-wives, novices > are led astray and are stuck with incorrect ideas about standing-waves > for the rest of the lives. > > Just change the name to TLI (Transmitter Loading Indicator) which is > what it is and does very well. The true meaning and associations of > SWR will then emerge and all will be flooded with the light of reason. > ---- > Reg, G4FGQ. Hi Reg I recognize that you know far more about VSWR and measuring complex load impedances than I do. I'm writing this to represent the "other side" of an arguement that states that VSWR *cant* be measured. I claim that VSWR *can* be measured and that VSWR can be used to identify the impedance terminating the transmission line. Jerry Article: 219569 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Message-ID: <6lIif.25353$Zv5.17910@newssvr25.news.prodigy.net> Date: Mon, 28 Nov 2005 18:51:46 GMT Jerry Martes wrote: > I claim that VSWR *can* be measured and that > VSWR can be used to identify the impedance terminating the transmission > line. The tuner SWR meter only indicates the SWR on the 50 ohm coax between the transmitter and the tuner. However, I have an SWR meter on the antenna side of my tuner and it does indeed indicate the SWR on my transmission line. XMTR--SWR meter#1--tuner--SWR meter#2--50 ohm coax to a G5RV SWR meter#2 does indeed indicate the SWR on the coax feed to my G5RV. It obviously does not indicate the SWR at the antenna. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219570 of rec.radio.amateur.antenna From: Bruce in Alaska Subject: Re: Station ground/2nd floor References: <4asjo1hv946ve2l5u17c1j8bmcruubei6t@4ax.com> <_cnif.19157$BZ5.14535@newssvr13.news.prodigy.com> <_Tnif.606420$xm3.396820@attbi_s21> <438A3123.AC0E860D@shaw.ca> <438A539F.B05A771D@shaw.ca> Message-ID: Date: Mon, 28 Nov 2005 18:55:08 GMT In article <438A539F.B05A771D@shaw.ca>, Irv Finkleman wrote: > Cecil Moore wrote: > > > > Irv Finkleman wrote: > > > Why not run two ground wires in parallel -- one twice as long as the > > > other? When one is Hi-Z the other will be Lo-Z and vice versa. > > > > That will help on some frequencies but it is akin to trying to > > erect a 1/2WL fan dipole for all frequencies - can't be done. Sooner > > or later, you will run into a frequency where length #1 is N*1/4WL > > and length #2 is (N+1)1/4WL. "It's not nice to fool Mother Nature." > > -- > > 73, Cecil http://www.qsl.net/w5dxp > > OK then, I'll use 3 wires and take my chances! :-) > > Irv If you are on in a building that has prestressed concrete floors, and coloums, try using the ReBar in the concrete as your RF Ground. When I built my house on a concrete slab, before the pour I brought up a steel strap bonded to the rebar and steel mesh in the radio room. it was a very effective RF Ground clear down to 500Khz. Bruce in alaska -- add a <2> before @ Article: 219571 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Date: Mon, 28 Nov 2005 19:36:28 GMT On Mon, 28 Nov 2005 17:54:35 GMT, "Jerry Martes" wrote: >that VSWR *cant* be measured. I claim that VSWR *can* be measured and that >VSWR can be used to identify the impedance terminating the transmission >line. Jerry, unless you redefine the term "impedance", you cannot generally measure impedance with a typical reflectometer style SWR meter. Impedance is a complex quantity (ie with real and imaginary parts). There are an infinite number of different impedances (being combinations of the real and imaginary parts) that could cause a given SWR on a given line in most cases. (The exception is the case when VSWR=1, you do know the impedance, it is the nominal Zo for which the instrument was calibrated.) Whilst you can work out the SWR that will result from a specific impedance on a specific Zo line, you cannot do the inverse, you don't have enough information. Owen -- Article: 219572 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Mon, 28 Nov 2005 20:10:13 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> "Jerry Martes" wrote > I'm writing this to represent the "other side" of an arguement that states > that VSWR *cant* be measured. I claim that VSWR *can* be measured and that > VSWR can be used to identify the impedance terminating the transmission > line. ======================================== The only way to measure SWR on a transmission line is to run a voltmeter along it. At least TWO measurements are needed. Not ONE. And line length is involved. The voltmeter readings will indeed tell you what the SWR is. But nothing else. It will be possible to calculate from the readings and the distance between max and min what the velocity of propagation is. But it is essential to add extra critical information before anything else can be deduced. Without this EXTRA information knowledge of the SWR (if it can be obtained) is useless. The so-called SWR meter does not and cannot provide this information. To calculate the terminating impedances from the SWR it is neccsary also to know the line impedance, its velocity and the exact locations of the max-volts and min-volts relative to the ends. The meter will not tell you. And the foregoing is on a line which exists only in one's imagination. I am sorry to repeat, the indications of the SWR meter apply only to the input impedance of the line from the transmitter to the antenna. The meter, in itself, tells you nothing about what is happening to conditions along the line. It certainly tells you nothing about the antenna's input impedance which is of primary interest. IF, BY SOME MEANS, YOU CAN MEASURE SWR, then there is much more information needed before the performance of the system can be predicted. The funny thing is - the performance of the system can be deduced >from the extra information without reference to the SWR. The whole business is laughable. Just change the name of the meter and all will become clear. ---- Reg, G4FGQ. Article: 219573 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Message-ID: Date: Mon, 28 Nov 2005 20:45:37 GMT Owen Duffy wrote: > wrote: >>that VSWR *cant* be measured. I claim that VSWR *can* be measured and that >>VSWR can be used to identify the impedance terminating the transmission >>line. > > Jerry, unless you redefine the term "impedance", you cannot generally > measure impedance with a typical reflectometer style SWR meter. Here's how I do it, Owen. I modified my SWR meter to tell me if the voltage sample is leading or lagging the current sample and if the voltage sample is greater or less than the current sample. Given the SWR is ratioed to 50 ohms, that's all I need. I adjust the length of my feedline until I find a current maximum point and the rest is easy. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219574 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Message-ID: <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> Date: Mon, 28 Nov 2005 20:49:07 GMT Reg Edwards wrote: > The only way to measure SWR on a transmission line is to run a > voltmeter along it. Reg, what about Rho = SQRT(P-/P+) and SWR=(1+Rho)/(1-Rho)? -- 73, Cecil http://www.qsl.net/w5dxp Article: 219575 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Mon, 28 Nov 2005 21:05:42 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <6lIif.25353$Zv5.17910@newssvr25.news.prodigy.net> "Cecil Moore" wrote > The tuner SWR meter only indicates the SWR on the 50 ohm coax > between the transmitter and the tuner. However, I have an SWR > meter on the antenna side of my tuner and it does indeed indicate > the SWR on my transmission line. > > XMTR--SWR meter#1--tuner--SWR meter#2--50 ohm coax to a G5RV > > SWR meter#2 does indeed indicate the SWR on the coax feed to > my G5RV. It obviously does not indicate the SWR at the antenna. ====================================== Cec, you are not telling the whole truth. The meter tells you nothing about the important main G5RV transmission line. ie., the SWR on the ladder line between the end of the coax and the antenna. Neither can it tell you what the antenna input impedance is. There are other ways of finding the input impedance of the G5RV antenna and its effect on line SWR if you should ever be sufficiently interested. You could use a computer program. ;o) ---- Reg. Article: 219576 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Date: Mon, 28 Nov 2005 21:14:32 GMT On Mon, 28 Nov 2005 20:45:37 GMT, Cecil Moore wrote: >Owen Duffy wrote: > >> wrote: >>>that VSWR *cant* be measured. I claim that VSWR *can* be measured and that >>>VSWR can be used to identify the impedance terminating the transmission >>>line. >> >> Jerry, unless you redefine the term "impedance", you cannot generally >> measure impedance with a typical reflectometer style SWR meter. > >Here's how I do it, Owen. I modified my SWR meter to tell me >if the voltage sample is leading or lagging the current sample >and if the voltage sample is greater or less than the current >sample. Given the SWR is ratioed to 50 ohms, that's all I need. >I adjust the length of my feedline until I find a current maximum >point and the rest is easy. Nice try Cecil. Note Jerry's statement: "VSWR can be used to identify the impedance terminating the transmission line". Your method, impractical as it is, means you have found a point where the impedance at the instrument terminals is purely resistive, and a minimum, and you are correct that you could calculate the value of that resistance. That measurement does not tell you the "impedance terminating the transmission line" unless the line is of zero length. You could make another measurement with another instrument (line length using a ruler) and using other knowledge, calculate the "impedance terminating the transmission line". In a practical situation, there is a risk that there is current flowing on the outer of a coaxial line or unbalance current in the case of an open wire line. In that case, changing the feedline length may affect the load impedance at the end of the line, so your proposed method may alter the very thing you are "measuring". Knowledge of the SWR AND the position of the standing wave pattern wrt the load AND the loss characteristics of the line is enough information to determine the "impedance terminating the transmission line"... but a typical reflectometer SWR meter does not measure all of those things. Owen -- Article: 219577 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Date: Mon, 28 Nov 2005 21:17:38 GMT On Mon, 28 Nov 2005 21:14:32 GMT, Owen Duffy wrote: >Knowledge of the SWR AND the position of the standing wave pattern wrt >the load AND the loss characteristics of the line is enough >information to determine the "impedance terminating the transmission >line"... but a typical reflectometer SWR meter does not measure all of >those things. Sorry, that should read: Knowledge of the SWR AND the position of the standing wave pattern wrt the load AND the transmission characteristics of the line is enough information to determine the "impedance terminating the transmission line"... but a typical reflectometer SWR meter does not measure all of those things. Owen -- Article: 219578 of rec.radio.amateur.antenna From: Over The Hill Subject: Re: Antennas-History (What's Going On?) References: <11okfpommc4nd0b@corp.supernews.com> Message-ID: Date: Mon, 28 Nov 2005 17:37:39 -0330 Roy Lewallen wrote: > How is any creative design accomplished? How did Armstrong come up with > the idea for FM, Watt for the steam engine? I've spent most of my career > doing circuit design, and it requires a deep knowledge of theory, but > also involves a creative synthesis not unlike what an artist has in > deciding what to paint or an architect in deciding what form a building > will take. Probably as well put as I've ever seen it and absolutely true. Look at antennas such as Log Periodic, Slot, Turnstile. The design Initially required more creative juices than engineering know-how. The engineering came after they were visually created in the mind. I know that to be a fact with the slot antenna. Some of the best engineers I have known, are those who visualize the function and then confirm it through calculation and measurement. In my opinion, these people are more like artists than engineers. For example, many people can put paint to canvas technically however, only an artist can use the paint to create what appears to be a living thing. The same holds true for engineers. The capable ones have the knowledge base. However, the really really good ones have something extra which is learned from books. Those are the special ones, the inventors. -- Over The Hill _____________________________________________________________________________ The question of whether computers can think is like the question of whether submarines can swim. ***Edsgar Dijkstra*** Article: 219579 of rec.radio.amateur.antenna From: Over The Hill Subject: Re: Antennas-History (What's Going On?) References: <11okfpommc4nd0b@corp.supernews.com> Message-ID: Date: Mon, 28 Nov 2005 17:42:07 -0330 Over The Hill wrote: > However, the really really good ones have something > extra which is learned from books. Those are the special ones, the > inventors. Sorry, should read: > However, the really really good ones have something > extra which is *not* learned from books. Those are the special ones, the > inventors. -- Over The Hill _____________________________________________________________________________ The question of whether computers can think is like the question of whether submarines can swim. ***Edsgar Dijkstra*** Article: 219580 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Mon, 28 Nov 2005 21:29:23 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> > Reg, what about Rho = SQRT(P-/P+) and SWR=(1+Rho)/(1-Rho)? ================================== Cec, That's a calculation, merely arithmetic, not a measurement. It applies only to a long line lossless line which does not exist but Zo must be 50 ohms. And nobody has the foggiest idea where max-volts and min-volts are located. And so the calculated information is useless except for trolling on newsgroups. ;o) ---- Reg. Article: 219581 of rec.radio.amateur.antenna From: Over The Hill Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> Message-ID: Date: Mon, 28 Nov 2005 17:54:57 -0330 Cecil Moore wrote: > Reg Edwards wrote: > >> The only way to measure SWR on a transmission line is to run a >> voltmeter along it. > > > Reg, what about Rho = SQRT(P-/P+) and SWR=(1+Rho)/(1-Rho)? If you know the forward and reflected power, VSWR can be calculated as follows: VSWR=(1+sqrt Pr/Pi) / (1-sqrt Pr/Pi) I believe. -- Over The Hill _____________________________________________________________________________ The question of whether computers can think is like the question of whether submarines can swim. ***Edsgar Dijkstra*** Article: 219582 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Mon, 28 Nov 2005 11:15:44 -0800 Message-ID: References: <11odjs54affpl83@corp.supernews.com> Roy Lewallen wrote: > Most authors explain how a wave is generated, then resort to reciprocity > to explain the reception process. But a clear and simple direct > explanation appears in Bailey, _TV and Other Receiving Antennas_ (pp. > 141-2), of what happens when an electromagnetic wave strikes a conductor: > > "The second, and equally important effect [the first being reflection of > much of the incident energy] is that some energy /does/ enter the outer > skin of the conductor. That part of the energy, which is not reflected, > must enter the conductor. The conditions at the surface of the > conductor, as we have already seen, give rise to a small resultant > electric vector and a large resultant magnetic vector. The presence of > these at the conductor is direct evidence that power is entering the > conductor. The small electric vector acts on the internal electrons of > the conductor and impresses a direction force, tending to drive the > electrons along the skin of the conductor in the direction of the > electric vector. But from experience we know that /no/ electrons can > ever be caused to move without gradually establishing their own magnetic > field, and this usually takes /time/. The motion of electrons (which is > electric current by definition) never takes place without the magnetic > field. How, then, is the electric vector from the electromagnetic wave > going to put these electrons in motion? It can only do so because the > electromagnetic wave /also supplies a magnetic vector/ as well as an > electric vector. And the value of this magnetic vector is exactly > proportioned to supply just the right amount of magnetic field energy > which the electrons require for immediate motion. Thus the electrons do > not have to establish their own magnetic field, since this field is > supplied by the electromagnetic wave. Hence, electromagnetic wave energy > entering the conductor establishes immediate motion of electrons /along/ > the conductor, the direction of motion at any instant corresponding to > the direction of the electric vector. If the electric vector changes > direction, the electrons will follow suit." Hi Roy - It's certainly true that a moving charge generates a magnetic field, so perhaps I'm reading it wrong. But it appears to me that Mr. Bailey is arguing here that an electron cannot be compelled to move simply by the application of an electric field. Do you think that is what he is saying? Do you agree? > Other posters have correctly pointed out that an antenna doesn't and > can't receive a signal solely due to the E field; Given the statement below, I would be interested to know how anyone could have tested the claim. ;-) > a time-changing E > field can't exist without an accompanying time-changing H field. > Roy Lewallen, W7EL Jim Kelley, AC6XG > Paul Taylor wrote: > >> Hi, >> >> I am looking for an explanation of how an antenna receives a signal due >> to the E-field of an electromagnetic wave. >> I have looked in some books, and can understand transmission, but the >> books I have looked in don't explain reception. >> I have found an explanation of how the H-field induces a signal in a loop >> antenna: a changing magnetic flux will induce a current. >> But what about the E-field and a dipole antenna? I guess that the E-field >> causes electrons to move in the antenna wire, because in a solid >> conductor, electrons will move until the E-field inside the solid is >> cancelled out? >> >> I have googled but having difficulty finding a good explanation. Any >> pointers? >> >> Thanks & regards, >> >> Paul. >> Article: 219583 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Mon, 28 Nov 2005 11:52:53 -0800 Message-ID: References: Reg Edwards wrote: > It is impossible for an E-field to exist without an H-field. Must have been before electrostatics was invented. :-) ac6xg Article: 219584 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Mon, 28 Nov 2005 14:31:36 -0800 Message-ID: <11on1ad29qr1841@corp.supernews.com> References: <11odjs54affpl83@corp.supernews.com> Jim Kelley wrote: > > Hi Roy - > > It's certainly true that a moving charge generates a magnetic field, so > perhaps I'm reading it wrong. But it appears to me that Mr. Bailey is > arguing here that an electron cannot be compelled to move simply by the > application of an electric field. Do you think that is what he is > saying? Do you agree? No, I don't believe he's saying that. He says, >> The small electric vector acts on the internal electrons of >> the conductor and impresses a direction force, tending to drive the >> electrons along the skin of the conductor in the direction of the >> electric vector. . . Roy Lewallen, W7EL Article: 219585 of rec.radio.amateur.antenna From: Over The Hill Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> Message-ID: <%nLif.2366$wf2.263110@news20.bellglobal.com> Date: Mon, 28 Nov 2005 18:49:39 -0330 Reg Edwards wrote: >>Reg, what about Rho = SQRT(P-/P+) and SWR=(1+Rho)/(1-Rho)? > > ================================== > Cec, That's a calculation, merely arithmetic, not a measurement. > > It applies only to a long line lossless line which does not exist but > Zo must be 50 ohms. And nobody has the foggiest idea where max-volts > and min-volts are located. And so the calculated information is > useless except for trolling on newsgroups. ;o) > ---- > Reg. Here are several VSWR measurement techniques. They are real they are valid and I used them for years. VSWR is a *very* important parameter, especially when dealing with high power systems. http://people.deas.harvard.edu/~jones/es151/lab_assign/lab_assign_3_98.pdf -- Over The Hill _____________________________________________________________________________ The question of whether computers can think is like the question of whether submarines can swim. ***Edsgar Dijkstra*** Article: 219586 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Mon, 28 Nov 2005 12:15:30 -0800 Message-ID: References: <11odjs54affpl83@corp.supernews.com> <11on1ad29qr1841@corp.supernews.com> Roy Lewallen wrote: > Jim Kelley wrote: > >> >> Hi Roy - >> >> It's certainly true that a moving charge generates a magnetic field, >> so perhaps I'm reading it wrong. But it appears to me that Mr. Bailey >> is arguing here that an electron cannot be compelled to move simply by >> the application of an electric field. Do you think that is what he is >> saying? Do you agree? > > > No, I don't believe he's saying that. He says, > > >> The small electric vector acts on the internal electrons of > >> the conductor and impresses a direction force, tending to drive the > >> electrons along the skin of the conductor in the direction of the > >> electric vector. . . Yes. But then he goes on to say, > How, then, is the electric vector from the electromagnetic wave going to put these electrons in motion? That's what I was referring to. Do you understand why he would pose this question if he believed he had already given the answer in the paragraph you quoted? He shoulda quit while he was ahead maybe? ;-) Thanks, Jim Kelley, AC6XG Article: 219587 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Message-ID: Date: Mon, 28 Nov 2005 23:52:40 GMT Owen Duffy wrote: > Your method, impractical as it is, ... "My method" was in widespread use before I was born. I learned it from my Elmer in the early 50's. He was always looking for that "magic" current maximum point to feed from his link coupled tank circuit. > ... means you have found a point where > the impedance at the instrument terminals is purely resistive, and a > minimum, and you are correct that you could calculate the value of > that resistance. That measurement does not tell you the "impedance > terminating the transmission line" unless the line is of zero length. A transmission line transforms the impedance in a predictable manner given the transmission line specifications. One can backtrack the SWR spiral on a Smith Chart to get a reasonable estimate for the antenna impedance. The impedances for my dipole calculated in such a manner are pretty close to the ones predicted by EZNEC. > In that case, changing the feedline length > may affect the load impedance at the end of the line, ... The load impedance is what it is, virtually unaffected by feedline length. > ... so your proposed > method may alter the very thing you are "measuring". Virtually every time one makes a measurement, one alters the very thing that one is measuring. That's just a fact of life and not a valid reason to give up trying to make measurements. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219588 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> Message-ID: <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Date: Tue, 29 Nov 2005 00:18:13 GMT Reg Edwards wrote: >>Reg, what about Rho = SQRT(P-/P+) and SWR=(1+Rho)/(1-Rho)? > > It applies only to a long line lossless line which does not exist but > Zo must be 50 ohms. Let's say we have the following system configuration with a 1:1 choke at '+': 100W XMTR---50 ohm coax---+---300 ohm twinlead---... Pfor1=100w--> Pfor2--> <--Pref1=0w <--Pref2 What's the forward power on the 300 ohm twinlead? What's the reflected power on the 300 ohm twinlead? What's the SWR on the 300 ohm twinlead? -- 73, Cecil http://www.qsl.net/w5dxp Article: 219589 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Subject: Re: SWR again. Message-ID: Date: Tue, 29 Nov 2005 01:28:24 GMT "Reg Edwards" wrote in message news:dmfo75$pf1$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > > "Jerry Martes" wrote >> I'm writing this to represent the "other side" of an arguement > that states >> that VSWR *cant* be measured. I claim that VSWR *can* be measured > and that >> VSWR can be used to identify the impedance terminating the > transmission >> line. > ======================================== > > The only way to measure SWR on a transmission line is to run a > voltmeter along it. At least TWO measurements are needed. Not ONE. > And line length is involved. > > The voltmeter readings will indeed tell you what the SWR is. But > nothing else. It will be possible to calculate from the readings and > the distance between max and min what the velocity of propagation is. > > But it is essential to add extra critical information before anything > else can be deduced. Without this EXTRA information knowledge of the > SWR (if it can be obtained) is useless. The so-called SWR meter does > not and cannot provide this information. > > To calculate the terminating impedances from the SWR it is neccsary > also to know the line impedance, its velocity and the exact locations > of the max-volts and min-volts relative to the ends. The meter will > not tell you. > > And the foregoing is on a line which exists only in one's imagination. > > I am sorry to repeat, the indications of the SWR meter apply only to > the input impedance of the line from the transmitter to the antenna. > The meter, in itself, tells you nothing about what is happening to > conditions along the line. It certainly tells you nothing about the > antenna's input impedance which is of primary interest. > > IF, BY SOME MEANS, YOU CAN MEASURE SWR, then there is much more > information needed before the performance of the system can be > predicted. > > The funny thing is - the performance of the system can be deduced > from the extra information without reference to the SWR. The whole > business is laughable. > > Just change the name of the meter and all will become clear. > ---- > Reg, G4FGQ. Hi Reg I have no understanding of why you find it important to state things that are not true about VSWR. VSWR *can* be measured. It is clear to me that you know that the Complex Impedance terminating a transmission line can determined by measuring the VSWR. Sure, it requires the position of the voltage mins (or maxs) be identified, with the load and then with a short ckt., and a Smith chart to be used for quick/easy identification of the load impedance. But, is that so much calculation that you find it necessary to state " IF, BY SOME MEANS, YOU CAN MEASURE SWR, then there is much more > information needed before the performance of the system can be > predicted". The load impedance isnt "predicted". It is actually *determined* with an accuracy associated with the precision of the test equipment. I consider measuring VSWR on a transmission line to be an excellent method of determining load impedance. Jerry Jerry Article: 219590 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Date: Tue, 29 Nov 2005 01:56:35 GMT On Mon, 28 Nov 2005 23:52:40 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> that resistance. That measurement does not tell you the "impedance >> terminating the transmission line" unless the line is of zero length. > >A transmission line transforms the impedance in a predictable >manner given the transmission line specifications. One can >backtrack the SWR spiral on a Smith Chart to get a reasonable >estimate for the antenna impedance. The impedances for my dipole To do that, you need to determine the position of the standing wave pattern with respect to the load, and a typical reflectometer style SWR meter does not do that. You could put a ruler to the line, but you are using another instrument to make a another measurement that the reflectometer could not make. It is misleading to suggest that a reflectometer style SWR meter alone is useful for determining the impede dance of a load connected to the meter by a length of transmission line, save possibly the case when VSWR=1 and the line is low loss and Zo is the same as the calibration Z of the SWR meter. Owen -- Article: 219591 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Message-ID: Date: Tue, 29 Nov 2005 02:47:51 GMT Owen Duffy wrote: > To do that, you need to determine the position of the standing wave > pattern with respect to the load, and a typical reflectometer style > SWR meter does not do that. Yes it does, if one has the ability to vary the length of the feedline until a current maximum point (minimum SWR) is known to be located at the balun/choke. I do it everytime I get on the air. That's how I tune my antenna system and I don't use any conventional tuner at all. > It is misleading to suggest that a reflectometer style SWR meter alone > is useful for determining the impedance of a load connected to the > meter by a length of transmission line, save possibly the case when > VSWR=1 and the line is low loss and Zo is the same as the calibration > Z of the SWR meter. Not misleading at all. I do it all the time. I know the exact length, velocity factor, and Z0 of my feedline. I know an SWR current maximum point is located at my choke. I know if it is greater than, less than, or equal to 50 ohms. It is a rather simple-minded process to accurately estimate the antenna feedpoint impedance given everything I know. You should try it sometime. Even if I didn't know if the current maximum impedance was lower than or higher than 50 ohms, there would only be two possible antenna impedances. EZNEC has a perfect track record in predicting which of those two antenna impedances actually exists. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219592 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Date: Tue, 29 Nov 2005 02:58:08 GMT Have it your way Cecil... Owen -- Article: 219593 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Tue, 29 Nov 2005 03:38:39 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Cecil, there's no need to rack your brains for hours trying to deduce the antenna input impedance from the input impedance of the transmission line. There's a computer program which will tell you the exact answer in milliseconds. Download program ZL_Zin from website below. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 219594 of rec.radio.amateur.antenna From: "Tom Donaly" Subject: Re: Antenna reception theory References: Message-ID: Date: Tue, 29 Nov 2005 04:09:43 GMT Jim Kelley wrote: > Reg Edwards wrote: > >> It is impossible for an E-field to exist without an H-field. > > > Must have been before electrostatics was invented. :-) > > ac6xg > > How do you make an electrostatic radio wave? 73, Tom Donaly, KA6RUH Article: 219595 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Tue, 29 Nov 2005 04:38:24 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Cec, The meter indicates SWR on the 50-ohm coax between meter and transmitter. It HAS to be 50-ohm coax. Any other impedance and you get the wrong answer. Without measurement of Zo = 50 ohms it can only be assumed. You then include in the calculation the measurement or assumption of the Zo of the 50-ohm coax, and the measurement or assumption of Zo of the twin-line, and the forward and reverse powers, and the SWR on the twin line can be deduced or assumed. But if you think you are measuring SWR on anything you are cheating and fooling yourself. In your particular case an assumptiom of Zo = 450 ohms for the twinline would be very much in error because both you and I know you have measured Zo to be 380 ohms. I can tell you what the SWR is on YOUR feedline without getting out of this armchair. I don't need to know your meter readings. ;o) ---- Reg. Article: 219596 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Tue, 29 Nov 2005 07:01:24 GMT "Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53) --- on the heady topic of "Re: Antenna reception theory" JK> From: Jim Kelley JK> Xref: core-easynews rec.radio.amateur.antenna:220506 JK> Reg Edwards wrote: > It is impossible for an E-field to exist without an H-field. JK> Must have been before electrostatics was invented. :-) Yes, but you are changing the topic into static fields. We were discussing changing electric fields, not statics but dynamics! A*s*i*m*o*v ... "Hey, I'm just this guy, see?" --Zaphod Beeblebrox Article: 219597 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Tue, 29 Nov 2005 07:19:47 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> "Jerry Martes" wrote > I have no understanding of why you find it important to state things that > are not true about VSWR. =================================== Jerry, It is important because the SWR meter is EDUCATIONAL. It is more than a pair of red and green LED's on our automatic tuners. All along I have stated that the name of the so-called SWR meter should be changed. Other more technical statements have been made to convince they whose state of mind prevents agreement. Remarkably few people disagree with my technical statements but offer no reasons for disagreement or prove me to be incorrect. SWR meters are by far the most prevelent topic on amateur radio newsgroups. It appears time and time again in contexts which demonstrate it to be a source of misunderstandings, arguments and general confusion. I maintain that the instrument's name is the root cause of the problems. It does not do what its name says it does. This inevitably leads people, not just novices and CB-ers, into incorrect channels of thought which become deeply ingrained. It unnecessarily introduces SWR into discussions which actually have nothing to do with SWR. And worst of all, when operating equipment, it causes people to have problems which either don't exist or are different to what people imagine they are. Mis-education is the keyword. Re-naming should begin in amateur radio handbooks and similar publications. Editors should be the first to be educated. SWR meters are seldom mentioned as such in professional text books. They are given other more correct names. Terman manages very well wthout them. But there's nothing wrong with his bibles. (Yes, I know they probably hadn't been invented in his day.) Perhaps when our Chinese friends enter the amateur radio market, manufacturers' wisdom will allow the light of reason to shine through. But they will have to get a move on. I can foresee the time when automatic tuners are universal and the only meter on black boxes will be the S-meter. I don't doubt that you thoroughly understand how the so-called SWR meter works. But even the present discussion is enough to demonstrate that a simple change is needed. In the end it all reduces to economics and survival of the fittest argument. ---- Reg, G4FGQ Article: 219598 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Tue, 29 Nov 2005 07:31:21 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Gerry, The load is the antenna - about which the SWR meter knows absolutely nothing. All the the meter has to work with is the input impedance of the tuner or the transmission line. Line input Z = R+jX and to aggravate matters the meter discards all information about X. ---- Reg. Article: 219599 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Tue, 29 Nov 2005 07:46:54 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Cecil, I note you have changed the name from "SWR Meter" to "Forward & Reverse Power Meter", a procedure I have been recommending for years. Congratulations! Although I am not altogether happy with your choice of new name. ---- Reg. Article: 219600 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 00:43:24 -0800 Message-ID: <11oo55f1oquge13@corp.supernews.com> References: <11odjs54affpl83@corp.supernews.com> <11on1ad29qr1841@corp.supernews.com> Jim Kelley wrote: > > Roy Lewallen wrote: > >> Jim Kelley wrote: >> >>> >>> Hi Roy - >>> >>> It's certainly true that a moving charge generates a magnetic field, >>> so perhaps I'm reading it wrong. But it appears to me that Mr. >>> Bailey is arguing here that an electron cannot be compelled to move >>> simply by the application of an electric field. Do you think that is >>> what he is saying? Do you agree? >> >> >> >> No, I don't believe he's saying that. He says, >> >> >> The small electric vector acts on the internal electrons of >> >> the conductor and impresses a direction force, tending to drive the >> >> electrons along the skin of the conductor in the direction of the >> >> electric vector. . . > > > Yes. But then he goes on to say, > >> How, then, is the electric vector from the electromagnetic wave going >> to put these electrons in motion? > > > That's what I was referring to. Do you understand why he would pose > this question if he believed he had already given the answer in the > paragraph you quoted? He shoulda quit while he was ahead maybe? ;-) Well, it's obvious that an electric field can move an electron. The Lorentz force law tells us how much force results from a given E field, and we can get the resulting acceleration from Newtonian physics. An everyday example is an oscilloscope deflection system which uses an electric field to deflect electrons. (Actually, modern digital scopes typically use raster displays with magnetic deflection -- but many of still have older analog types with electric field deflection.) But if the antenna conductor were perfect, no E field at all could exist at the wire surface regardless of the amplitude of the E field of the oncoming wave. The wave's E field therefore couldn't directly influence the electrons in the (perfect) conductor. Only the H field of the wave, then, can induce a current in the perfect conductor. The direct influence of the E field on an imperfect conductor would be highly dependent on the conductivity of the wire, and I'd guess it would be very small compared to the influence of the H field from a typical oncoming wave on an electron in a good conductor. Maybe that's what he was saying. Roy Lewallen, W7EL Article: 219601 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: C. Crane's Twin Ferrite Antenna Message-ID: <51ooo1d1k89d5tif3s29h1uqe41e2uranc@4ax.com> References: Date: Tue, 29 Nov 2005 14:07:16 GMT On Tue, 29 Nov 2005 11:36:09 GMT, "W. Watson" wrote: > excerpted... > >I'll continue to experiment, but so far not so good. Comments? You've already got an 8" ferrite bar antenna in the C.Crane radio; perhaps the twin-doozie deal just doesn't add that much. bob k5qwg Article: 219602 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Message-ID: Date: Tue, 29 Nov 2005 14:14:15 GMT Owen Duffy wrote: > Have it your way Cecil... I hope you now see the advantage of being able to vary the length of the ladder-line until a current maximum point is located at the choke-balun. Knowing the impedance is purely resistive and relatively low allows me to read it with my MFJ-259B. That resistive point is on the ladder-line SWR circle on the Smith Chart. An arc of the SWR circle is the known length of the feedline which gives me the feedpoint impedance of the antenna (and can be adjusted for losses). -- 73, Cecil http://www.qsl.net/w5dxp Article: 219603 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antennas-History (What's Going On?) References: <7955-438B368C-194@storefull-3256.bay.webtv.net> Message-ID: Date: Tue, 29 Nov 2005 14:28:05 GMT Richard Clark wrote: > wrote: >>A book by that title was not found on Amazon. You're not thinking of the >>latest edition of his "Antennas" are you? "for all applications" is part of a subtitle. > Amazon is a poor start. Try a real book vendor: > http://www.alibris.com/search/search.cfm?qwork=349517&wtit=%22Antennas%20for%20All%20Applications&ptit=Antennas%20for%20All%20Applications&pauth=Kraus%2C%20John%20Daniel%2C%20and%20Leet%2C%20Kenneth%20J&pisbn=&pqty=3&pqtynew=3&pbest=84%2E18&pbestnew=84%2E18&matches=3&qsort=r&cm_re=works*listing*title > where there are three available. You may not like the price, however. Prices ($31) are good here: http://dogbert.abebooks.com/servlet/SearchResults?y=11&isbn=0072321032&x=44 -- 73, Cecil http://www.qsl.net/w5dxp Article: 219604 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Message-ID: Date: Tue, 29 Nov 2005 15:02:15 GMT Reg Edwards wrote: > You then include in the calculation the measurement or assumption of > the Zo of the 50-ohm coax, and the measurement or assumption of Zo of > the twin-line, and the forward and reverse powers, and the SWR on the > twin line can be deduced or assumed. Actually, nowadays I use my MFJ-259B to read the resistance at the choke-balun where I have adjusted the ladder-line length to guarantee the existence of a current maximum point. It's actually easier to do than to write about it. An assumption that Z0=50 ohms is not necessary. > But if you think you are measuring SWR on anything you are cheating > and fooling yourself. I actually have an SWR meter calibrated for balanced 380 ohms but it's in a box somewhere in my garage. I found my indirect measurements to be entirely accurate enough. In general, if one can isolate the problem to 10% of the Smith Chart, one can solve any problem by tweaking. Speaking of indirect measurements - let's say the feedline Z0 is 380 ohms with a VF of 0.9 and a length of 90 ft. The measured resistance at the current maximum point is 30 ohms on 7.15 MHz. The SWR on the ladder-line is 380/30 = 12.7:1. The feedline is 0.727 wavelengths long. Plot the point 30/380 = 0.079 + j0 on a Smith Chart. Draw an SWR circle through that point. Backtrack from that point around the circle for 0.727 wavelengths and there's your antenna feedpoint impedance (neglecting losses). Losses can be taken into account by using SWR spirals instead of SWR circles. And of course, all of this is done by a computer program after just a few seconds of data entry. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219605 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Tue, 29 Nov 2005 15:03:44 GMT Asimov wrote: > Yes, but you are changing the topic into static fields. We were > discussing changing electric fields, not statics but dynamics! When is someone going to come up with a context-free language? -- 73, Cecil http://www.qsl.net/w5dxp Article: 219606 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Message-ID: <78_if.19423$BZ5.11218@newssvr13.news.prodigy.com> Date: Tue, 29 Nov 2005 15:06:43 GMT Reg Edwards wrote: > Line input Z = R+jX and to aggravate matters the meter discards all > information about X. All the more reason to feed the line at a current maximum point where X is known to be zero. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219607 of rec.radio.amateur.antenna From: "Jeff Dieterle" Subject: Am Antenna Help Date: Tue, 29 Nov 2005 10:15:37 -0500 Message-ID: <11oos4qo1fo1dd2@corp.supernews.com> I'm inside an office inside an old brick and steel factory and can get very little AM reception, only a few of the stations located in the same city. I ran RG6-U coax to the roof of the factory (appx.100ft) and considered buying a loop antenna but at this groups suggestion connected the coax to a long wire. The stations I'm interested in are Indianapolis 1070kc and Chicago 670kc & 1000kc. I installed 200ft of #12ga insulated wire that is orientated in line with these 2 cities and 6' above the roof at the terminations and 3-4' in the center. I grounded the coax shield at the roof and in my office and I'm using a GE Superadio III on batteries. I can get these stations fine in the daytime with a reasonable amount of static but at night the static increases severely. Is there anything else I can do to make this a better antenna. Thanks in Advance Jeff Article: 219608 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Message-ID: Date: Tue, 29 Nov 2005 15:16:32 GMT Reg Edwards wrote: > Cecil, I note you have changed the name from "SWR Meter" to "Forward & > Reverse Power Meter", a procedure I have been recommending for years. > Congratulations! I think that was probably used to describe the Bird which, to the best of my knowledge, has no SWR scale on the meter face. Now my Autek WM-1 actually has an "SWR meter" on the front panel in addition to the "watt meter". I don't use a tuner and it computes the actual SWR on the RG-213 going to my G5RV. I achieve an SWR very close to 1:1 on the RG-213 on all HF bands by varying the length of the balanced series section. 36 feet of ladder-line works for 40m and 17m, my two favorite bands. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219609 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: <1l_if.19425$BZ5.1171@newssvr13.news.prodigy.com> Date: Tue, 29 Nov 2005 15:20:29 GMT W. Watson wrote: > Putting a new PSU in a PC about a month ago > increased the noise in AM radios 70-100' from the PC to an almost > unacceptable level. Why do you think that's a radio problem? :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219610 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 10:31:40 -0600 Message-ID: <28496-438C826C-805@storefull-3257.bay.webtv.net> References: <11oo55f1oquge13@corp.supernews.com> Roy, W7EL wrote: "But, if the antenna conductor were perfect, no E field at all could exist at the wire surface regardless of the magnitude of the E field of the oncoming wave." If we have a non-varying E field, a perfect conductor in the field would have the same voltage everywhere due to the short-circuit connecting all points. But, an electromagnetic wave sweeping the wire has an alternating electric field. Its phase is uniform (the same) across the wavefront because all points are equidistant from the source. A wire parallel to the E vector would simultaneously experience the same E field force throughout its length. "No E field at all could exist at the wire surface regardless of the magnitude of the E field of the oncoming wave," Why must the wire be perfect? Best regards, Richard Harrison, KB5WZI Article: 219611 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Subject: Re: SWR again. Message-ID: Date: Tue, 29 Nov 2005 17:54:45 GMT "Reg Edwards" wrote in message news:dmgvej$104$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > > "Jerry Martes" wrote >> I have no understanding of why you find it important to state things > that >> are not true about VSWR. > > =================================== > Jerry, > > It is important because the SWR meter is EDUCATIONAL. It is more than > a pair of red and green LED's on our automatic tuners. > > All along I have stated that the name of the so-called SWR meter > should be changed. Other more technical statements have been made to > convince they whose state of mind prevents agreement. > > Remarkably few people disagree with my technical statements but offer > no reasons for disagreement or prove me to be incorrect. > > SWR meters are by far the most prevelent topic on amateur radio > newsgroups. It appears time and time again in contexts which > demonstrate it to be a source of misunderstandings, arguments and > general confusion. > > I maintain that the instrument's name is the root cause of the > problems. It does not do what its name says it does. This inevitably > leads people, not just novices and CB-ers, into incorrect channels of > thought which become deeply ingrained. It unnecessarily introduces > SWR into discussions which actually have nothing to do with SWR. And > worst of all, when operating equipment, it causes people to have > problems which either don't exist or are different to what people > imagine they are. Mis-education is the keyword. > > Re-naming should begin in amateur radio handbooks and similar > publications. Editors should be the first to be educated. > > SWR meters are seldom mentioned as such in professional text books. > They are given other more correct names. Terman manages very well > wthout them. But there's nothing wrong with his bibles. (Yes, I know > they probably hadn't been invented in his day.) > > Perhaps when our Chinese friends enter the amateur radio market, > manufacturers' wisdom will allow the light of reason to shine through. > But they will have to get a move on. I can foresee the time when > automatic tuners are universal and the only meter on black boxes will > be the S-meter. > > I don't doubt that you thoroughly understand how the so-called SWR > meter works. But even the present discussion is enough to demonstrate > that a simple change is needed. In the end it all reduces to > economics and survival of the fittest argument. > ---- > Reg, G4FGQ Naw Reg, I dont have the slightest idea how a "VSWR meter" works. I was too quick with my response about the worth of VSWR. I thought the discussion was aimed toward the VSWR itself. I've got to re-read that story about Silence is Golden and put it to practice. Jerry Article: 219612 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 10:01:23 -0800 Message-ID: References: Tom Donaly wrote: > Jim Kelley wrote: > >> Reg Edwards wrote: >> >>> It is impossible for an E-field to exist without an H-field. >> >> >> >> Must have been before electrostatics was invented. :-) >> >> ac6xg >> >> > > How do you make an electrostatic radio wave? > 73, > Tom Donaly, KA6RUH Certainly you're aware that radio waves don't have a monopoly on E fields, Tom. 73, jk Article: 219613 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 10:09:37 -0800 Message-ID: References: <11odjs54affpl83@corp.supernews.com> <11on1ad29qr1841@corp.supernews.com> <11oo55f1oquge13@corp.supernews.com> Roy Lewallen wrote: > Well, it's obvious that an electric field can move an electron. The > Lorentz force law tells us how much force results from a given E field, > and we can get the resulting acceleration from Newtonian physics. An > everyday example is an oscilloscope deflection system which uses an > electric field to deflect electrons. (Actually, modern digital scopes > typically use raster displays with magnetic deflection -- but many of > still have older analog types with electric field deflection.) Yes, I thought that much was obvious as well. > But if the antenna conductor were perfect, no E field at all could exist > at the wire surface regardless of the amplitude of the E field of the > oncoming wave. The wave's E field therefore couldn't directly influence > the electrons in the (perfect) conductor. Only the H field of the wave, > then, can induce a current in the perfect conductor. The direct > influence of the E field on an imperfect conductor would be highly > dependent on the conductivity of the wire, and I'd guess it would be > very small compared to the influence of the H field from a typical > oncoming wave on an electron in a good conductor. Maybe that's what he > was saying. > > Roy Lewallen, W7EL It could be what he was saying. But conductors are are called conductors for a reason, and it's not necessarily because they conduct magnetic fields well. 73, ac6xg Article: 219614 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Tue, 29 Nov 2005 18:17:01 GMT Jim Kelley wrote: > Certainly you're aware that radio waves don't have a monopoly on E > fields, Tom. But they should have a monopoly on threads in this newsgroup. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 219615 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 10:26:08 -0800 Message-ID: References: Asimov wrote: > "Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53) > --- on the heady topic of "Re: Antenna reception theory" > > JK> From: Jim Kelley > JK> Xref: core-easynews rec.radio.amateur.antenna:220506 > > JK> Reg Edwards wrote: > > > It is impossible for an E-field to exist without an H-field. > > JK> Must have been before electrostatics was invented. :-) > > > Yes, but you are changing the topic into static fields. We were > discussing changing electric fields, not statics but dynamics! But do you agree that it's not impossible for an E field to exist without an H field? ac6xg Article: 219616 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Tue, 29 Nov 2005 18:37:09 GMT Jim Kelley wrote: > But do you agree that it's not impossible for an E field to exist > without an H field? Depends upon the context. I suspect he was talking within the context of RF EM waves? Is it possible for an RF E-field to exist without an RF H-field? -- 73, Cecil http://www.qsl.net/w5dxp Article: 219617 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: Am Antenna Help Date: 29 Nov 2005 19:04:47 GMT Message-ID: References: <11oos4qo1fo1dd2@corp.supernews.com> On Tue, 29 Nov 2005 10:15:37 -0500, Jeff Dieterle wrote: > I'm inside an office inside an old brick and steel factory and can get very > little AM reception, only a few of the stations located in the same city. I > ran RG6-U coax to the roof of the factory (appx.100ft) and considered buying > a loop antenna but at this groups suggestion connected the coax to a long > wire. The stations I'm interested in are Indianapolis 1070kc and Chicago > 670kc & 1000kc. I installed 200ft of #12ga insulated wire that is orientated > in line with these 2 cities and ..... ^^^^^^^ ??????? In-line? The wire should be broadside to the desired path of propagation. > ... I can get these stations fine > in the daytime with a reasonable amount of static but at night the static > increases severely. Is there anything else I can do to make this a better > antenna. You never mention how far away you are from "... Indianapolis 1070kc and Chicago 670kc & 1000kc." That'll have a LARGE bearing on the day/night reception question. Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 219618 of rec.radio.amateur.antenna From: Allodoxaphobia Subject: Re: C. Crane's Twin Ferrite Antenna Date: 29 Nov 2005 19:09:32 GMT Message-ID: References: On Tue, 29 Nov 2005 11:36:09 GMT, W. Watson wrote: > I bought this antenna on a 30 day trial, and just got it about 12 hours ago. > So far I'm not at all impressed. I live about 150 miles from an AM station, > at 810, in the SF/SJ Bay Area, which has a marginal signal, but usually > listenable. Putting a new PSU in a PC about a month ago increased the noise > in AM radios 70-100' from the PC to an almost unacceptable level. I had > hoped the antenna would boost the signal enough to knock down the noise. The 'noise' is _also_ a signal -- just one that nobody wants to receive. The "C. Crane's Twin Ferrite Antenna" happily 'improves' the reception of the noise -- in addition to the signal(s) you desire. Let me guess: That PSU was "Made in China". Jonesy -- Marvin L Jones | jonz | W3DHJ | linux Pueblo, Colorado | @ | Jonesy | OS/2 __ 38.24N 104.55W | config.com | DM78rf | SK Article: 219619 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 14:22:42 -0500 Message-ID: References: Tom Donaly wrote: > Jim Kelley wrote: > >> Reg Edwards wrote: >> >>> It is impossible for an E-field to exist without an H-field. >> >> >> >> Must have been before electrostatics was invented. :-) >> >> ac6xg >> >> > > How do you make an electrostatic radio wave? Wave to it first? - 73 de Mike KB3EIA - Article: 219620 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: C. Crane's Twin Ferrite Antenna Date: Tue, 29 Nov 2005 14:27:29 -0500 Message-ID: References: W. Watson wrote: > I bought this antenna on a 30 day trial, and just got it about 12 hours > ago. So far I'm not at all impressed. I live about 150 miles from an AM > station, at 810, in the SF/SJ Bay Area, which has a marginal signal, but > usually listenable. Putting a new PSU in a PC about a month ago > increased the noise in AM radios 70-100' from the PC to an almost > unacceptable level. I had hoped the antenna would boost the signal > enough to knock down the noise. There are times when I can get a good > signal from the station, but certainly less frequently than before. Any rf noise put out by the computer ps is going to be picked up by your antenna as well as the radio station you are trying to hear. So a better antenna (if your new one is indeed better) wil just pick up stronger power supply noise. It's moslty a null situation. What you need to do is get that power supply fixed or replaced - 73 de Mike KB3EIA - Article: 219621 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 11:31:05 -0800 Message-ID: <11opb3rakuceo3d@corp.supernews.com> References: <11oo55f1oquge13@corp.supernews.com> <28496-438C826C-805@storefull-3257.bay.webtv.net> Richard Harrison wrote: > Roy, W7EL wrote: > "But, if the antenna conductor were perfect, no E field at all could > exist at the wire surface regardless of the magnitude of the E field of > the oncoming wave." > > If we have a non-varying E field, a perfect conductor in the field would > have the same voltage everywhere due to the short-circuit connecting all > points. > > But, an electromagnetic wave sweeping the wire has an alternating > electric field. Its phase is uniform (the same) across the wavefront > because all points are equidistant from the source. A wire parallel to > the E vector would simultaneously experience the same E field force > throughout its length. "No E field at all could exist at the wire > surface regardless of the magnitude of the E field of the oncoming > wave," > > Why must the wire be perfect? A time-varying E field can exist in a non-perfect conductor; it cannot exist in a perfect conductor. You can find the explanation for why this is in any electromagnetics text. Roy Lewallen, W7EL Article: 219622 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: inter-reaction of hf antennas on a small lot Date: Tue, 29 Nov 2005 14:36:54 -0500 Message-ID: References: <1133289708.761566.263730@g44g2000cwa.googlegroups.com> Paladin wrote: > Dear Group, > I have two "main" antennas that I use in my small > lot. About 1/8 0f an acre > or say 70ft. wide by 140ft. deep. There are utility lines on one > side of my property. > One of the antennas is a full-wave loop for 80m. It is up about > 30ft.,and feed at the > feedpoint by a 4/1 balun into good coax to the shack. The other > antenna is a dipole; > 140ft long feed by ladderline to the shack. I have a tower(60ft) > and a couple of small uhf and vhf beams also. > My question IS how are the near-fields and the far fields > INTEREACTING with the other antennas ? What does one antenna DO the > the transmit or recieve of > the other ? How close can these antennas be to each other? Interesting. During the PAQSO party we had a similar situation as we were operating 2 stations simultaneously. As far as I know, the answer is "not much" on transmit. Less on recieve. Now if you are trying to use both stations at the same time, there can be a lot of problems. Our antennas were a tribander used on 20 meters, and a 40 meter dipole. We were both running power, and the 40 meter station was reaking havoc with me on 20 meters. I made a stub to put on the 20 meter rig, and all was harmony. The distance from the dipole to the tribander was areound 40 feet at closest rotation angle. >What problems will I get because there is NOT enough space in between the elements ? Do you mean on the beams? Article: 219623 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 11:42:05 -0800 Message-ID: References: Cecil Moore wrote: > Jim Kelley wrote: > >> But do you agree that it's not impossible for an E field to exist >> without an H field? > > > Depends upon the context. I suspect he was talking within the > context of RF EM waves? That's certainly a context where an E field is always accompanied by an H field. But the statement as it was written is nevertheless untrue. That was my only point. > Is it possible for an RF E-field to > exist without an RF H-field? Seems to beg an obvious answer. But the question brings up a point that people seem to be missing here. An E field is an E field - there are not different 'kinds' of E fields. The field itself is the same, whether it varies in time or not. A non-zero dE/dt allows for some of the more interesting properties to have non-zero solutions, but the fields themselves are not unique. I hope that concept isn't too controversial for this group. If it is, I will strive to keep such ideas to myself in the future. ac6xg Article: 219624 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 12:28:02 -0800 Message-ID: References: Cecil Moore wrote: > Jim Kelley wrote: > >> The field itself is the same, whether it varies in time or not. > > > I wonder if that's true when taken out of context? :-) > > I'm no physicist but wouldn't a static electric field > be made up of virtual photons while a dynamic electric > field would be made up of non-virtual photons? Non-virtual photons, as opposed virtual non-photons I presume. I think physicists know they're going to have to wait until they get to the pearly gates before they can really learn what "electric fields are made out of". ;-) 73, jk Article: 219625 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Date: Tue, 29 Nov 2005 20:37:00 GMT On Tue, 29 Nov 2005 14:14:15 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Have it your way Cecil... > >I hope you now see the advantage of being able to vary the >length of the ladder-line until a current maximum point is >located at the choke-balun. Knowing the impedance is purely >resistive and relatively low allows me to read it with my >MFJ-259B. That resistive point is on the ladder-line SWR circle >on the Smith Chart. An arc of the SWR circle is the known length >of the feedline which gives me the feedpoint impedance of the >antenna (and can be adjusted for losses). Cecil, you have a single solution, and you are inclined to transform every problem to require that single solution (read your posts). Whilst step variable length transmission lines have application, they are not the solution to every problem, or indeed, to many problems. You are not the originator, nor the only user of such. Since you mention the Smith chart, you are a champion of operating transmission lines at very high VSWR, and yet would suggest that a Smith chart can give you an adequate solution for the losses. That says more of what you consider adequate than the suitability of the Smith chart as a solver of that type of problem, especially in this day and age. I suggest that the Smith chart loss solution is adequate when you can ignore the losses. I can visualise you sitting amidst an expensive heap of inch size pieces of LDF5-50 and a Bird 43, slide rule and Smith chart, with a caption "It is possible, and it is practical!". Yes, you could say that I understand the advantages of a step variable length transmission line. It is probably why they are used as much as they are. Owen -- Article: 219626 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> Date: Tue, 29 Nov 2005 20:46:24 GMT On Tue, 29 Nov 2005 15:02:15 GMT, Cecil Moore wrote: >Reg Edwards wrote: >> You then include in the calculation the measurement or assumption of >> the Zo of the 50-ohm coax, and the measurement or assumption of Zo of >> the twin-line, and the forward and reverse powers, and the SWR on the >> twin line can be deduced or assumed. > >Actually, nowadays I use my MFJ-259B to read the resistance at >the choke-balun where I have adjusted the ladder-line length to >guarantee the existence of a current maximum point. It's actually >easier to do than to write about it. An assumption that Z0=50 ohms >is not necessary. > >> But if you think you are measuring SWR on anything you are cheating >> and fooling yourself. > >I actually have an SWR meter calibrated for balanced 380 ohms but it's >in a box somewhere in my garage. I found my indirect measurements to >be entirely accurate enough. In general, if one can isolate the problem >to 10% of the Smith Chart, one can solve any problem by tweaking. > >Speaking of indirect measurements - let's say the feedline Z0 is 380 >ohms with a VF of 0.9 and a length of 90 ft. The measured resistance >at the current maximum point is 30 ohms on 7.15 MHz. The SWR on the >ladder-line is 380/30 = 12.7:1. The feedline is 0.727 wavelengths >long. Plot the point 30/380 = 0.079 + j0 on a Smith Chart. Draw an >SWR circle through that point. Backtrack from that point around the >circle for 0.727 wavelengths and there's your antenna feedpoint >impedance (neglecting losses). Losses can be taken into account by >using SWR spirals instead of SWR circles. And of course, all of this >is done by a computer program after just a few seconds of data entry. So what is the answer to your example, the load Z, with and without consideration of the losses? -- Article: 219627 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 12:40:18 -0800 Message-ID: References: Cecil Moore wrote: > Jim Kelley wrote: > >> Certainly you're aware that radio waves don't have a monopoly on E >> fields, Tom. > > > But they should have a monopoly on threads in this newsgroup. :-) Methinks you ridicule the optically disinclined, Cecil. ac6xg Article: 219628 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Tue, 29 Nov 2005 21:01:43 GMT "Jim Kelley" bravely wrote to "All" (29 Nov 05 10:26:08) --- on the heady topic of "Re: Antenna reception theory" JK> From: Jim Kelley JK> Xref: core-easynews rec.radio.amateur.antenna:220548 JK> Asimov wrote: > "Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53) > --- on the heady topic of "Re: Antenna reception theory" > > JK> From: Jim Kelley > JK> Xref: core-easynews rec.radio.amateur.antenna:220506 > > JK> Reg Edwards wrote: > > > It is impossible for an E-field to exist without an H-field. > > JK> Must have been before electrostatics was invented. :-) > > > Yes, but you are changing the topic into static fields. We were > discussing changing electric fields, not statics but dynamics! JK> But do you agree that it's not impossible for an E field to exist JK> without an H field? A static E field can exist alone but to detect it requires something like a field-mill which basically converts it into a changing EM field that can be readily detected. A simple field-mill is basically a rapidly spinning antenna. Relativity at work. A*s*i*m*o*v ... The truth is WAY out there! Article: 219629 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: C. Crane's Twin Ferrite Antenna Message-ID: References: Date: Tue, 29 Nov 2005 21:01:47 GMT "Tim Wescott" bravely wrote to "All" (29 Nov 05 09:16:58) --- on the heady topic of "Re: C. Crane's Twin Ferrite Antenna" TW> From: Tim Wescott TW> Xref: core-easynews rec.radio.amateur.antenna:220543 [,,,] TW> Generally if you have atmospheric or man-made noise increasing the TW> antenna efficiency is just going to increase the noise along with the TW> signal. TW> You could try to make a directional antenna; this would increase your TW> desired signal more than your noise. [,,,] I wonder if it would help putting up a short vertical and summing its signal with such polarity that it cancels the noise from the main directive antenna? This on the theory that most man-made noise is by its nature vertically polarized. A*s*i*m*o*v ... If you're not making waves, you're not rowing the boat Article: 219630 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Message-ID: Date: Tue, 29 Nov 2005 21:35:33 GMT Owen Duffy wrote: > So what is the answer to your example, the load Z, with and without > consideration of the losses? Sorry, I just got a new Dell and don't have my software loaded. A quick pencil whipping of a Smith Chart graph yields a load around 1140 - j1900 ohms which would be about right for a 145 ft. dipole on 40m. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219631 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <5kmmo1tmlbj5s3chhgqi5a0a7tk35ggj4s@4ax.com> Message-ID: Date: Tue, 29 Nov 2005 21:43:01 GMT Owen Duffy wrote: > Cecil, you have a single solution, and you are inclined to transform > every problem to require that single solution (read your posts). No, my solution allows me to pull Reg's leg in arguments about SWR meters since I don't use a tuner. :-) My solution also allows me to get by without a 500 watt tuner for my SGC-500. The other advantages are just frosting on the cake. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219632 of rec.radio.amateur.antenna From: Jim Higgins Subject: Re: SWR again. Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <6lIif.25353$Zv5.17910@newssvr25.news.prodigy.net> Date: Tue, 29 Nov 2005 21:50:27 GMT On Mon, 28 Nov 2005 21:05:42 +0000 (UTC), "Reg Edwards" wrote: > >"Cecil Moore" wrote >> The tuner SWR meter only indicates the SWR on the 50 ohm coax >> between the transmitter and the tuner. However, I have an SWR >> meter on the antenna side of my tuner and it does indeed indicate >> the SWR on my transmission line. >> >> XMTR--SWR meter#1--tuner--SWR meter#2--50 ohm coax to a G5RV >> >> SWR meter#2 does indeed indicate the SWR on the coax feed to >> my G5RV. It obviously does not indicate the SWR at the antenna. >====================================== > >Cec, you are not telling the whole truth. > >The meter tells you nothing about the important main G5RV transmission >line. ie., the SWR on the ladder line between the end of the coax and >the antenna. Neither can it tell you what the antenna input impedance >is. Why would one be concerned with the SWR at that point unless one is trying to adjust the ladder line length or impedance, or the antenna dimensions, for optimum impedance - presumably 50 ohmn - at that point? In the real world a properly constructed G5RV is only a decent match on one band and an excellent match only on a narrow portion of that band... if you're lucky. Everywhere else you need an antenna tuner and when you do the point of interest is the end of the coax where it attaches to the tuner. If you disagree, please explain why, clearly. Article: 219633 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 15:43:49 -0600 Message-ID: <26586-438CCB95-839@storefull-3253.bay.webtv.net> References: Reg, G4FGQ wrote: "It is impossible for an E-field to exist without an H-field." Agreed. By definition an electromagnetic wave includes an electric component and a magnetic component. That does not mean the components are inseparable. The purpose of a Faraday screen is to eliminate capacitive coupling while permitting magnetic coupling. I`ve worked in several medium wave broadcast plants. In these, each tower was coupled through a 1:1 air-core transformer to its transmission line. The transformer consisted of two identical coils, one on either side of a Faraday screen. The coils shared a cmmon axis. Electrically, the transformer was transparent at the transmitting frequency. It coupled the transmitting frequency as if the transformer did not exist to impede. Its purpose was to eliminate capacitive coupling, The Faraday screen provided a place where electric field lines are shunted to ground. The problem with capacitive coupling between a transmitter and a tower is that the higher the frequency, the less the reactance or opposition. The coupling is better through a capacitance to the harmonics of a frequency than it is for the fundamental. The Faraday screen removes this unwanted bias for imroved harmonic propagation. A side effect of the Faraday screen is that it removes lightning strokes before they reach the transmission line from the tower. The Faraday screen looks like a metal rake. Its back where the teeth or tines join is firmly grounded. The teeth are open-circuited. Current cannot circulate between and through the teeth, so no counter electromotive force can be generated to oppose magnetic coupling between primary and secondary coils. The rake is transparent for magnetic coupling but it is a stopper for electric coupling. By complete shielding, that is metalllically enclosihng one or both coils of an impedance coupling pair, magneric coupling between them can be practically eliminated. A coupling capacitor between the coils allows only the electric field to be effective. There`s no magnetic field involved. I`m no advocate of the E-H antenna, but the electric and magnetic components of a wave are easily separated. Best regards, Richard Harrison, KB5WZI Article: 219634 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <3fkpo1578sa6nejfr47umsq10d970jqjkc@4ax.com> References: <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Date: Tue, 29 Nov 2005 22:27:17 GMT On Tue, 29 Nov 2005 21:35:33 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> So what is the answer to your example, the load Z, with and without >> consideration of the losses? > >Sorry, I just got a new Dell and don't have my software loaded. >A quick pencil whipping of a Smith Chart graph yields a >load around 1140 - j1900 ohms which would be about right >for a 145 ft. dipole on 40m. You didn't differentiate between the lossy and lossless solutions. The difference isn't very much, I figure about 1100-j2000 vs 1000-j2170 which is real hard to resolve on the Smith chart. Smith chart programs solve the same tranmission line problems as underlies the Smith chart, but using a program provides much higher resolution, and the convenience and accuracy benefit of not having to find the solution in a normalised domain. The Smith chart does not directly indicate the mismatch loss in the general case. My online calculator at http://www.vk1od.net/tl/tllce.php produces an answer (considering loss) of 422.87-j1441.91 if the transmission line was 90' Wireman 552 and using Wes's characterisation of 552 for derivation of the fundamental line parameters (slightly different Zo to yours). Indicated line loss is 0.93 dB. (SWR is not used to arrive at the solution.) Dan's TLD gives 432.7-j1459.0 using a slightly different transmission line approximation, and independently deriving the model from Wes's characterisation. Indicated line loss is 0.93 dB. This demonstrates the sensitivity of the result to very slight variations in line parameters, consideration of loss, and the approximations used in modelling. Owen -- Article: 219635 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Subject: Re: SWR again. Message-ID: Date: Tue, 29 Nov 2005 22:30:16 GMT "Owen Duffy" wrote in message news:1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com... > On Tue, 29 Nov 2005 15:02:15 GMT, Cecil Moore wrote: > >>Reg Edwards wrote: >>> You then include in the calculation the measurement or assumption of >>> the Zo of the 50-ohm coax, and the measurement or assumption of Zo of >>> the twin-line, and the forward and reverse powers, and the SWR on the >>> twin line can be deduced or assumed. >> >>Actually, nowadays I use my MFJ-259B to read the resistance at >>the choke-balun where I have adjusted the ladder-line length to >>guarantee the existence of a current maximum point. It's actually >>easier to do than to write about it. An assumption that Z0=50 ohms >>is not necessary. >> >>> But if you think you are measuring SWR on anything you are cheating >>> and fooling yourself. >> >>I actually have an SWR meter calibrated for balanced 380 ohms but it's >>in a box somewhere in my garage. I found my indirect measurements to >>be entirely accurate enough. In general, if one can isolate the problem >>to 10% of the Smith Chart, one can solve any problem by tweaking. >> >>Speaking of indirect measurements - let's say the feedline Z0 is 380 >>ohms with a VF of 0.9 and a length of 90 ft. The measured resistance >>at the current maximum point is 30 ohms on 7.15 MHz. The SWR on the >>ladder-line is 380/30 = 12.7:1. The feedline is 0.727 wavelengths >>long. Plot the point 30/380 = 0.079 + j0 on a Smith Chart. Draw an >>SWR circle through that point. Backtrack from that point around the >>circle for 0.727 wavelengths and there's your antenna feedpoint >>impedance (neglecting losses). Losses can be taken into account by >>using SWR spirals instead of SWR circles. And of course, all of this >>is done by a computer program after just a few seconds of data entry. > > So what is the answer to your example, the load Z, with and without > consideration of the losses? Hi Owen Did you mean to write the load impedance as 0.079 + j0? Or did you mean 0.079 + j1? Jerry Article: 219636 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Tue, 29 Nov 2005 22:36:22 GMT W. Watson wrote: > > I'll continue to experiment, but so far not so good. Comments? As others have said, you should try to attenuate the noise at its source. If it is radiated, you need a better PSU. If it is coming out on the PCs AC line, line filters might help. If the PC and KGO are not in the same direction, some sort of directional antenna might help. Of course, the ultimate solution would be to move to SF and get a really big signal. But there are problems with that, too: I live abt 3-4 miles west of KNX (50 KW, 1070 KHz) and my problem is avoiding it, not making it stonger :) Phil Article: 219637 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 14:40:31 -0800 Message-ID: <11opm73g4plt772@corp.supernews.com> References: <26586-438CCB95-839@storefull-3253.bay.webtv.net> I'm afraid your Faraday screen might not work quite like you think it does. In the vicinity of the screen, the E field is indeed reduced. However, you haven't stripped off the E field from the EM wave, or separated it. The E field is largely reflected from the screen, but out of phase with the original wave. So the E/H ratio is smaller on *both* sides of the screen. Close to the screen, much of the energy formerly in the E field has been transferred to the H field. But as you go beyond the screen in either direction, you'll find the E field increasing and the H field decreasing as the energy redistributes itself. Within a short distance (typically considerably less than a wavelength, but depending on the size of the screen), the ratio of E/H will again be close to 377 ohms, assuming air is the surrounding medium. The Faraday screen works in the broadcast application only because the "shielded" component is close to the screen, where the E/H ratio is low. In other words, you can modify the E/H ratio in a small region of space by moving the energy from one to the other. But you can't separate the two components or eliminate one or the other. This is of course referring to time-varying, not static, fields. Reg's statement is technically false, since he didn't say whether the fields are time-varying -- static E and H fields can independently exist. But time-varying E and H fields, which I'm sure is what he meant, can't. Roy Lewallen, W7EL Richard Harrison wrote: > Reg, G4FGQ wrote: > "It is impossible for an E-field to exist without an H-field." > > Agreed. > > By definition an electromagnetic wave includes an electric component and > a magnetic component. That does not mean the components are inseparable. > > The purpose of a Faraday screen is to eliminate capacitive coupling > while permitting magnetic coupling. > > I`ve worked in several medium wave broadcast plants. In these, each > tower was coupled through a 1:1 air-core transformer to its transmission > line. The transformer consisted of two identical coils, one on either > side of a Faraday screen. The coils shared a cmmon axis. > > Electrically, the transformer was transparent at the transmitting > frequency. It coupled the transmitting frequency as if the transformer > did not exist to impede. Its purpose was to eliminate capacitive > coupling, The Faraday screen provided a place where electric field lines > are shunted to ground. > The problem with capacitive coupling between a transmitter and a tower > is that the higher the frequency, the less the reactance or opposition. > The coupling is better through a capacitance to the harmonics of a > frequency than it is for the fundamental. The Faraday screen removes > this unwanted bias for imroved harmonic propagation. > > A side effect of the Faraday screen is that it removes lightning strokes > before they reach the transmission line from the tower. > > The Faraday screen looks like a metal rake. Its back where the teeth or > tines join is firmly grounded. The teeth are open-circuited. Current > cannot circulate between and through the teeth, so no counter > electromotive force can be generated to oppose magnetic coupling between > primary and secondary coils. The rake is transparent for magnetic > coupling but it is a stopper for electric coupling. > > By complete shielding, that is metalllically enclosihng one or both > coils of an impedance coupling pair, magneric coupling between them can > be practically eliminated. A coupling capacitor between the coils allows > only the electric field to be effective. There`s no magnetic field > involved. > > I`m no advocate of the E-H antenna, but the electric and magnetic > components of a wave are easily separated. > > Best regards, Richard Harrison, KB5WZI > Article: 219638 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Tue, 29 Nov 2005 14:46:41 -0800 Message-ID: References: "Asimov" wrote: > A static E field can exist alone but to detect it requires something > like a field-mill which basically converts it into a changing EM field > that can be readily detected. A simple field-mill is basically a > rapidly spinning antenna. Relativity at work. It's similar in some ways to a method for detecting magnetic fields used prior to the advent of Hall effect devices. Not sure how it relates to relativity. Perhaps it's true that an electric field is simpler create than to detect by direct means. But it isn't really any more difficult than, for example, measuring power by direct means. I think Ben Franklin measured the E field in a Leyden Jar by calibrating the leaf displacement caused by the Coulomb force resulting from the electric field between the two similarly charged surfaces. jk Article: 219639 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Message-ID: Date: Tue, 29 Nov 2005 23:12:52 GMT Jerry Martes wrote: > Did you mean to write the load impedance as 0.079 + j0? Or did you mean > 0.079 + j1? 0.079 + j0 is the normalized impedance at a current maximum point at the transmitter. The load impedance is not given. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219640 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Subject: Re: SWR again. Message-ID: Date: Tue, 29 Nov 2005 23:31:38 GMT "Cecil Moore" wrote in message news:Uf5jf.26479$Zv5.16509@newssvr25.news.prodigy.net... > Jerry Martes wrote: >> Did you mean to write the load impedance as 0.079 + j0? Or did you >> mean 0.079 + j1? > > 0.079 + j0 is the normalized impedance at a current > maximum point at the transmitter. The load impedance > is not given. > -- > 73, Cecil http://www.qsl.net/w5dxp I have *no* excuse for my not being able to read and think. i did re-read the post and see whats being done. Jerry Article: 219641 of rec.radio.amateur.antenna From: "Dale Parfitt" References: Subject: Re: C. Crane's Twin Ferrite Antenna Message-ID: Date: Tue, 29 Nov 2005 23:43:06 GMT "Tim Wescott" wrote in message news:ZcKdneDicvRpERHenZ2dnUVZ_sednZ2d@web-ster.com... > W. Watson wrote: >> I bought this antenna on a 30 day trial, and just got it about 12 hours >> ago. So far I'm not at all impressed. I live about 150 miles from an AM >> station, at 810, in the SF/SJ Bay Area, which has a marginal signal, but >> usually listenable. Putting a new PSU in a PC about a month ago increased >> the noise in AM radios 70-100' from the PC to an almost unacceptable >> level. I had hoped the antenna would boost the signal enough to knock >> down the noise. There are times when I can get a good signal from the >> station, but certainly less frequently than before. >> >> The antenna consists of three parts: a 600-1800 KHz control dial, a >> ferrite antenna and something called the antenna element. The latter is >> about 8" long by 3" by 1.5" (high). The idea is that one puts the ferrite >> antenna very near the radio and the antenna element in some other spot, >> then adjusts the control dial to the max strength. I detect zero change >> in any AM signal from the (C. Crane) radio anywhere on the dial. The >> antenna element can be grounded. I modestly did this by hooking a wire >> (alligator clips) from the element to the ground socket of an AC outlet >> (nail in the socket). No change. BTW, when I was doing the experiment >> last evening, the signal was pretty decent during that period. In fact, >> quite listenable. All this without the device though. >> >> I'll continue to experiment, but so far not so good. Comments? > > I'd change the power supply to a better brand. > > Generally if you have atmospheric or man-made noise increasing the antenna > efficiency is just going to increase the noise along with the signal. > > You could try to make a directional antenna; this would increase your > desired signal more than your noise. > > The antenna would have to be big, however. The wavelength at 800kHz is > somewhere around 370 meters and you'd need to use around 1/4 of this. > The ferrite antennas are already directional. That is one of their advantages. > You could try to feed power supply noise to the radio antenna at just the > right amplitude and phase to null it out. This would be a good subject > for an undergraduate or even a Master's thesis in EE but probably not a > good thing to do in practice. These devices are well known and sold at least by 2 ham manufacturers- MFJ and Timewave(?). Dale W4OP Article: 219642 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1133311300.421664.127270@g44g2000cwa.googlegroups.com> Subject: Re: Stacking Satellite VHF and UHF F9FT Antennas Date: Tue, 29 Nov 2005 21:34:38 -0500 Message-ID: <1761b$438d0fc1$97d56a33$7844@ALLTEL.NET> If everything is perfect, you will have an additional 3 dB gain. wrote in message news:1133311300.421664.127270@g44g2000cwa.googlegroups.com... > Hello all, > > I actually own a 2x9 VHF and a 2x19 UHF by F9FT (Tonna). > Since I need better performance (especially on VHF) for LEO operations > I was thinking about stacking another antenna identical to the one I > already have. > The suggested stacking distance is 2.77 m. Since I am doing this > upgrade I tought about stacking another UHF antenna too so that I would > have an horizontal mast 3 meters long, with the VHF yagis at the ends > and the UHF yagis in the middle. > > I have some questions: > 1) Will the UHF yagis create troubles to the VHF since they are in the > middle? > 2) What kind of real performance increase will I experience on VHF? > 3) Can I couple the vertical elements with a coupler and the horizontal > elements with another coupler and then apply a RCHP/LCHP coupling > harness like I would normally do on a single antenna? > > Thanks > > Alain De Carolis > iz6byy ww3ww > Article: 219643 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 02:54:34 GMT Tim Wescott wrote: > W. Watson wrote: > >> I bought this antenna on a 30 day trial, and just got it about 12 >> hours ago. So far I'm not at all impressed. I live about 150 miles ... snip >> during that period. In fact, quite listenable. All this without the >> device though. >> >> I'll continue to experiment, but so far not so good. Comments? > > > I'd change the power supply to a better brand. > > Generally if you have atmospheric or man-made noise increasing the > antenna efficiency is just going to increase the noise along with the > signal. > > You could try to make a directional antenna; this would increase your > desired signal more than your noise. > > The antenna would have to be big, however. The wavelength at 800kHz is > somewhere around 370 meters and you'd need to use around 1/4 of this. > > You could try to feed power supply noise to the radio antenna at just > the right amplitude and phase to null it out. This would be a good > subject for an undergraduate or even a Master's thesis in EE but > probably not a good thing to do in practice. > > You could attempt to shield it. Rat Shack has some clamp-on ferrites, > you could put one of these on your power cord close to the end that > plugs into the power supply. You could also make sure that the PC case > is well shielded. > I tried the RS ferrites and they made no change. I even took barbell weights and put them on the AC line of the PC. Zippo. If I hadn't already spent $60 for the new PSU six weeks ago, I might think of buying a much better one. In some way this may be circuit dependent. I do believe I plugged in my other PC to the same socket and had the same experience; however, when it's plugged into its normal socket, there is no noticeable change. Interestingly, bad weather moved in yesterday and today, and reception from the station has been quite good with the normal antenna. This stuff can get pretty strange. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219644 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 02:59:54 GMT Michael Coslo wrote: > W. Watson wrote: > >> I bought this antenna on a 30 day trial, and just got it about 12 >> hours ago. So far I'm not at all impressed. I live about 150 miles >> from an AM station, at 810, in the SF/SJ Bay Area, which has a >> marginal signal, but usually listenable. Putting a new PSU in a PC >> about a month ago increased the noise in AM radios 70-100' from the PC >> to an almost unacceptable level. I had hoped the antenna would boost >> the signal enough to knock down the noise. There are times when I can >> get a good signal from the station, but certainly less frequently than >> before. > > > Any rf noise put out by the computer ps is going to be picked up by > your antenna as well as the radio station you are trying to hear. So a > better antenna (if your new one is indeed better) wil just pick up > stronger power supply noise. It's moslty a null situation. > > What you need to do is get that power supply fixed or replaced > > - 73 de Mike KB3EIA - > I think the only solutions to the PSU problem is to buy a much better one. As I mention above, that's probably a losing proposition. I doubt after 6 weeks they would take it back. It might be worth a try though. Note my comment above to someone a few moments ago that this seems to be a household circuit dependent problem. Another PC in the same room works fine until I plug it into the socket that I first noticed the problem. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219645 of rec.radio.amateur.antenna Message-ID: <438D1515.2030703@invalid.com> From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: Date: Wed, 30 Nov 2005 02:57:14 GMT Allodoxaphobia wrote: > On Tue, 29 Nov 2005 11:36:09 GMT, W. Watson wrote: > >>I bought this antenna on a 30 day trial, and just got it about 12 hours ago. >>So far I'm not at all impressed. I live about 150 miles from an AM station, >>at 810, in the SF/SJ Bay Area, which has a marginal signal, but usually >>listenable. Putting a new PSU in a PC about a month ago increased the noise >>in AM radios 70-100' from the PC to an almost unacceptable level. I had >>hoped the antenna would boost the signal enough to knock down the noise. > > > The 'noise' is _also_ a signal -- just one that nobody wants to receive. > The "C. Crane's Twin Ferrite Antenna" happily 'improves' the reception > of the noise -- in addition to the signal(s) you desire. > > Let me guess: That PSU was "Made in China". > > Jonesy Yes, you absolutely guessed the right country. I called the tech support and they were less than useful. I asked about a circuit diagram. Sorry, we don't have one to give out. The trick here is that I see absolutely no change at all. One would think maybe the volume might increase, but nay. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219646 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 03:05:03 GMT W. Watson wrote: > > In some way this may be circuit dependent. I do believe I plugged in my > other PC to the same socket and had the same experience; however, when > it's plugged into its normal socket, there is no noticeable change. > Grounding issue? Article: 219647 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 03:06:18 GMT W. Watson wrote: > Phil Wheeler wrote: > >> W. Watson wrote: >> >>> >>> I'll continue to experiment, but so far not so good. Comments? >> >> >> >> As others have said, you should try to attenuate the noise at its >> source. If it is radiated, you need a better PSU. If it is coming >> out on the PCs AC line, line filters might help. >> >> If the PC and KGO are not in the same direction, some sort of >> directional antenna might help. >> >> Of course, the ultimate solution would be to move to SF and get a >> really big signal. But there are problems with that, too: I live abt >> 3-4 miles west of KNX (50 KW, 1070 KHz) and my problem is avoiding it, >> not making it stonger :) >> >> Phil > > Yes, I've had that experience with close stations. You can probably > listen to it through the bed springs. :-) > I hope not: Still use a water bed :) > Attempts to shield the AC with the RS ferrite block and a barbell weight > failed. See comment about household circuit dependency in my just posted > responses above yours. > Got it! Article: 219648 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: C. Crane's Twin Ferrite Antenna Date: Wed, 30 Nov 2005 03:42:32 -0000 Message-ID: <11oq7t8ks5btc2d@corp.supernews.com> References: In article , W. Watson wrote: >I tried the RS ferrites and they made no change. I even took barbell weights >and put them on the AC line of the PC. Zippo. If I hadn't already spent $60 >for the new PSU six weeks ago, I might think of buying a much better one. Ferrites clamped around the power cable will help with common-mode RF noise. They won't do anything to help cancel out differential-mode noise. It'd probably be beneficial for you to try to get a robust powerline noise filter. These will filter out both common-mode noise, and differential noise as well. Unfortunately, it's possible that the new power supply is radiating RF directly, rather than feeding it back into the mains. If so, nothing other than replacing it, or switching to a PC case with better shielding, is likely to help the problem. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! Article: 219649 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 03:44:17 GMT Richard Clark wrote: > On Wed, 30 Nov 2005 02:54:34 GMT, "W. Watson" > wrote: > > >>Interestingly, bad weather moved in yesterday and today, and reception from >>the station has been quite good with the normal antenna. This stuff can get >>pretty strange. > > > Classic indication of a bad ground, or a ground loop. > > 73's > Richard Clark, KB7QHC If so, how do I track it down? -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219650 of rec.radio.amateur.antenna From: Howard Subject: Re: C. Crane's Twin Ferrite Antenna Date: Tue, 29 Nov 2005 20:14:39 -0800 Message-ID: References: On Wed, 30 Nov 2005 03:02:10 GMT, "W. Watson" wrote: >Phil Wheeler wrote: > >> W. Watson wrote: >> >>> >>> I'll continue to experiment, but so far not so good. Comments? >> >> >> As others have said, you should try to attenuate the noise at its >> source. If it is radiated, you need a better PSU. If it is coming out >> on the PCs AC line, line filters might help. >> >> If the PC and KGO are not in the same direction, some sort of >> directional antenna might help. >> >> Of course, the ultimate solution would be to move to SF and get a really >> big signal. But there are problems with that, too: I live abt 3-4 miles >> west of KNX (50 KW, 1070 KHz) and my problem is avoiding it, not making >> it stonger :) >> >> Phil >Yes, I've had that experience with close stations. You can probably listen >to it through the bed springs. :-) > >Attempts to shield the AC with the RS ferrite block and a barbell weight >failed. See comment about household circuit dependency in my just posted >responses above yours. Wayne, You may wish to get one of those $5 circuit analyzers from your local Lowe's/Home Depot/Tools R Us (yes, I realize this probably means a drive to Grass Valley) and check for open ground connections on all your sockets. I had grounding issues at my home and after getting a shock while adjusting the hot water in the shower brought in an electrician. He found many problems such as the hot and return shorting on the bathtub (behind the wall of course where it can't be seen) and most of my outlets did not have a ground. Had the house re-wired and it got a bit more RF friendly - hope you find your issue and don't have to rewire the house. BTW, Nevada City is a nice place to call home - if you bump into Mayor Arnett tell him that Howard from LA says hi. Howard Article: 219651 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: C. Crane's Twin Ferrite Antenna Date: Tue, 29 Nov 2005 20:34:26 -0800 Message-ID: <11oqaunilqhkn99@corp.supernews.com> References: <11oq7t8ks5btc2d@corp.supernews.com> Dave Platt wrote: > In article , > W. Watson wrote: > > >>I tried the RS ferrites and they made no change. I even took barbell weights >>and put them on the AC line of the PC. Zippo. If I hadn't already spent $60 >>for the new PSU six weeks ago, I might think of buying a much better one. > > > Ferrites clamped around the power cable will help with common-mode RF > noise. They won't do anything to help cancel out differential-mode > noise. Differential mode radiation is almost never a problem in situations like this. The differential mode component of the noise, by definition, is >from equal and opposite noise currents on the two conductors (of the power line, for example). For this mode, the conductors comprise a transmission line, and radiation will be extremely small because the fields from the two very close and parallel conductors are equal in magnitude and opposite in direction. Ferrites are a good suggestion, but the ones commonly used for RFI suppression are of a ferrite type which doesn't have an awful lot of attenuation as low as the AM broadcast band. Best would be some Fair-Rite 70 series, or other ferrite with an initial permeability of several thousand. Best would be to get a large core and wrap multiple turns on it with the power cord, as close to the PC as possible. This way, you get a lot more impedance than clamping cores onto the wire, since the impedance is proportional to the square of the number of turns. That is, 10 turns on a single core gives you the same impedance as 100 of the same cores clamped onto the cable. > It'd probably be beneficial for you to try to get a robust powerline > noise filter. These will filter out both common-mode noise, and > differential noise as well. A good power line filter isn't a bad idea, but differential mode filtering won't make any appreciable difference. > > Unfortunately, it's possible that the new power supply is radiating RF > directly, rather than feeding it back into the mains. If so, nothing > other than replacing it, or switching to a PC case with better > shielding, is likely to help the problem. To radiate any significant amount of energy requires some sort of antenna, so a power supply won't radiate much on its own. The trick, then, is to prevent the noise from getting from its source to the antenna. The most likely antenna is the power line, but any other wires connected to the computer can also serve this function. I'd start by disconnecting everything from the computer except the power line, getting the noise down with ferrites or a power line filter, then connecting one thing at a time and applying ferrites to the other wires as required. If wires inside the computer are acting as the antenna, the computer box should contain the noise to a high degree -- if you still have noise with only the power line connected and filtered, check the integrity of the computer case. Look for any seams that don't have good metal-to-metal contact between pieces. Roy Lewallen, W7EL Article: 219652 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <84gqo1pg64hh6n170mup6h0unn7g6tstil@4ax.com> References: <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> Date: Wed, 30 Nov 2005 06:03:43 GMT On Tue, 29 Nov 2005 22:30:16 GMT, "Jerry Martes" wrote: > Did you mean to write the load impedance as 0.079 + j0? Or did you mean >0.079 + j1? I didn't write that, it was Cecil, and j0 would be correct. Owen -- Article: 219653 of rec.radio.amateur.antenna From: Over The Hill Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <1133265193.300163.189900@g44g2000cwa.googlegroups.com> Message-ID: Date: Wed, 30 Nov 2005 09:30:56 -0330 Saandy , 4Z5KS wrote: > ...if already going into it, a little bit of history. > when the cows had bigger heads and the air was greener, there was no > such thing as coax. what we used was the ubiquitous ladder wire, with > an unknown impedance and with a frequency response depending on what > the Gods ate at lunch! the VSWR story was not invented yet. > What we did was one of two things: either tune the system for maximum > current in the line or else used a light bulb in conjunction with a > small light bulb and tuned for maximum brilliance. in neither case was > SWR involved in the mess. > the whole SWR uproar began after WW2 with the advent of coax and the > new fangled theories. that was also the time when all kind of > directional couplers came up.in due time a few wise guys developed all > kinds of theories on the subject, and manged to convey the impression > that SWR is king! nothing further from truth. what's really true is > that reflections can cause the apparent impedance at the network's > input to differ from Zo. SO WHAT? if you can adjust your matching > network between the transmitter and the line for a match what do you > care? > actually the hitch is that, with a high SWR on the line, the losses go > up. if the cable can take it, without melting no harm's done: whatever > remains will get radiated. this was the good pint of open feeders: the > losses were very low. an SWR fo 10 and more was insignificant from the > losses' point ov view. > Guys, leave it alone! Just make sure that the SWR is a reasonable > value, something that the transmitter can handle and leave it at that. > Saandy 4Z5KS Some of what you say is very true. Especially in the world of HAM radio. How ever, this being an open forum, truth is of great importance. Your thesis on the "whys" of the importance of vswr measurements are incorrect in some areas. Yes, importance grew with the advent of coaxial lines simply because of the relatively small distances between inner and outer conductors. That part is true. However, until you've seen a 6" universal coaxial transmission line with no insulators or inner conductor remaining over a 350" run, I guess you can't really appreciate the need for monitoring and maintaining good "system" vswr characteristics. Now to the measuring of said vswr. It can be done. In the broadcast world it's accomplished through the measurement of "Return Loss". By measuring the system return loss at the line input (generator end) and deducting twice the line attenuation, we get an indication of the load return loss thesis value is easily converted to vswr. Return Loss: This is the dB value of absolute reflection coefficient. It is rather curious concept of transmission engineering. This loss value becomes 0 for 100% reflection and becomes infinite for an ideal connection. RL = 20log((VSWR+1) / (VSWR-1)) Voltage Standing Wave Ratio (VSWR): This is the ratio of maximum voltage to minimum voltage in standing wave pattern. It varies from +1 to infinite. VSWR = (1+(10^RL/20)) / ((10^RL/20)-1) These are good and valid measurements which should be performed at initial installation of the system and periodically verified throughout the system life. Return Loss/VSWR is only one of many measurements that should be periodically done. DC measurements such as megger. LO-Ohms are also very important. -- Over The Hill _____________________________________________________________________________ The question of whether computers can think is like the question of whether submarines can swim. ***Edsgar Dijkstra*** From - Thu Dec 1 05:11:04 EST 2005 Article: 219654 of rec.radio.amateur.antenna From: "Thierry" <-> Newsgroups: rec.radio.amateur.antenna Subject: website about DXpeditions ? Date: Wed, 30 Nov 2005 14:17:31 +0100 Lines: 22 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-RFC2646: Format=Flowed; Original NNTP-Posting-Host: tvsurf-habscht1-247.pt.lu Message-ID: <438da66c$1@news.vo.lu> X-Trace: news.vo.lu 1133356652 213.166.42.247 (30 Nov 2005 14:17:32 +0100) Path: news1.isis.unc.edu!elk.ncren.net!news2.wam.umd.edu!nntp.abs.net!newsfeed.cw.net!cw.net!news-FFM2.ecrc.de!news.rh-tec.net!news.n-ix.net!npeer.de.kpn-eurorings.net!news.vo.lu!not-for-mail Xref: news1.isis.unc.edu rec.radio.amateur.antenna:219654 Hi, Simple question, Is there somewhere on the Internet a website dedicated to the release of stories about DXpeditions (I think well to ARRL but their text is quite small), there are CQ and QST but its on paper and not dedicated, but rather a website covering most of these activities and in anotehr way that simply listing the date of their QRV (membres, qsl, date, story, rig, etc, etc) ? Thanks in advance Thierry ON4SKY http://www.astrosurf.org/lombry -- Auteur de "Un siècle de Physique, 1- La Physique Quantique", AEGEUS, 2005 My FAQ : http://www.astrosurf.org/lombry/faq-lombry.htm Article: 219655 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: <_dmdnW6NerbRuRDeRVn-ug@adelphia.com> Message-ID: <8Ehjf.2255$YT3.1169@newsread3.news.pas.earthlink.net> Date: Wed, 30 Nov 2005 13:17:56 GMT Mike Coslo wrote: > W. Watson wrote: > >> Michael Coslo wrote: >> >>> W. Watson wrote: >>> >>>> I bought this antenna on a 30 day trial, and just got it about 12 >>>> hours ago. So far I'm not at all impressed. I live about 150 miles >>>> from an AM station, at 810, in the SF/SJ Bay Area, which has a >>>> marginal signal, but usually listenable. Putting a new PSU in a PC >>>> about a month ago increased the noise in AM radios 70-100' from the >>>> PC to an almost unacceptable level. I had hoped the antenna would >>>> boost the signal enough to knock down the noise. There are times >>>> when I can get a good signal from the station, but certainly less >>>> frequently than before. >>> >>> >>> >>> >>> Any rf noise put out by the computer ps is going to be picked up >>> by your antenna as well as the radio station you are trying to hear. >>> So a better antenna (if your new one is indeed better) wil just pick >>> up stronger power supply noise. It's moslty a null situation. >>> >>> What you need to do is get that power supply fixed or replaced >>> >>> - 73 de Mike KB3EIA - >>> >> I think the only solutions to the PSU problem is to buy a much better >> one. As I mention above, that's probably a losing proposition. I doubt >> after 6 weeks they would take it back. It might be worth a try though. >> Note my comment above to someone a few moments ago that this seems to >> be a household circuit dependent problem. Another PC in the same room >> works fine until I plug it into the socket that I first noticed the >> problem. > > > > Hmmm, just maybe, you might be able to ditch it as a warranty item. > Dunno tho' as it will depend on the outfit that sold it to you. I don't > know if you are a Ham or not, but if you are, you might play the part 15 > card, as they are required to not interfere. I suspect that a 160 meter > rig might catch the same interference. > > It is kind of a drag though, since IIRC a noisy switcher Power > supply is hard to fix. Good luck! > > - 73 de Mike KB3EIA - I'm tempted, but somehow your message gave me another idea. I think I'm going to take the PC to an entirely different location miles from here and see if get the same problem. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219656 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: Date: Wed, 30 Nov 2005 13:26:37 GMT Howard wrote: > On Wed, 30 Nov 2005 03:02:10 GMT, "W. Watson" > wrote: > > >>Phil Wheeler wrote: >> >> >>>W. Watson wrote: >>> >>> >>>>I'll continue to experiment, but so far not so good. Comments? >>> >>> >>>As others have said, you should try to attenuate the noise at its >>>source. If it is radiated, you need a better PSU. If it is coming out >>>on the PCs AC line, line filters might help. >>> >>>If the PC and KGO are not in the same direction, some sort of >>>directional antenna might help. >>> >>>Of course, the ultimate solution would be to move to SF and get a really >>>big signal. But there are problems with that, too: I live abt 3-4 miles >>>west of KNX (50 KW, 1070 KHz) and my problem is avoiding it, not making >>>it stonger :) >>> >>>Phil >> >>Yes, I've had that experience with close stations. You can probably listen >>to it through the bed springs. :-) >> >>Attempts to shield the AC with the RS ferrite block and a barbell weight >>failed. See comment about household circuit dependency in my just posted >>responses above yours. > > > Wayne, > You may wish to get one of those $5 circuit analyzers from your local > Lowe's/Home Depot/Tools R Us (yes, I realize this probably means a > drive to Grass Valley) and check for open ground connections on all > your sockets. I had grounding issues at my home and after getting a > shock while adjusting the hot water in the shower brought in an > electrician. He found many problems such as the hot and return > shorting on the bathtub (behind the wall of course where it can't be > seen) and most of my outlets did not have a ground. Had the house > re-wired and it got a bit more RF friendly - hope you find your issue > and don't have to rewire the house. > > BTW, Nevada City is a nice place to call home - if you bump into > Mayor Arnett tell him that Howard from LA says hi. > > Howard Ah, you know about us. I'm not a ham, but I will be speaking to our local club in January about radio astronomy. I used to have my hair cut by the former mayor. I'll have to ask my present barber if he frequents her shop. Maybe he attends the ham meetings. I only go to them when I want to promote RA, which has been 3 times. Although I went a few weeks ago to find out if anyone had a Icom R7000 rcvr. No luck. However, my opportunity to buy one disappeared within a few days of that meeting. I may have one of those analyzers here somewhere. Lowe's is a long way from here, but we have one very good hardware store that would be a good candidate. -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219657 of rec.radio.amateur.antenna From: "W. Watson" Subject: Re: C. Crane's Twin Ferrite Antenna References: <1l_if.19425$BZ5.1171@newssvr13.news.prodigy.com> <7N9jf.21327$7h7.17117@newssvr21.news.prodigy.com> Message-ID: Date: Wed, 30 Nov 2005 13:33:20 GMT Cecil Moore wrote: > W. Watson wrote: > >> Cecil Moore wrote: >> >>> Why do you think that's a radio problem? :-) >> >> >> When I turn the computer off, the radio station noise drops >> dramatically. It doesn't matter if I use AC or DC. I can detect the >> large noise change in my car from the garage. > > > That sounds like a computer problem, not a radio problem. > What am I missing? Probably nothing. However, I'd be willing to bet that I wouldn't have this problem if I were 100 miles closer to the radio station. The Crane device has been so ineffective its baffling as an issue aside from the one about my radio. I built an FM signal booster when I was 14 that showed more promise. Well, I've got 28 more days to return it. If it shows nothing more, I will be out about $7.00 for return postage--rental fee? -- Wayne T. Watson (Watson Adventures, Prop., Nevada City, CA) (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time) Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet Traveling in remote places in the winter. What's the best tool to carry with you? An axe. -- Survivorman, Discovery (SCI) Channel Web Page: Article: 219658 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Wed, 30 Nov 2005 15:12:19 GMT "Jim Kelley" bravely wrote to "All" (29 Nov 05 14:46:41) --- on the heady topic of "Re: Antenna reception theory" JK> From: Jim Kelley JK> Xref: core-easynews rec.radio.amateur.antenna:220573 JK> "Asimov" wrote: > A static E field can exist alone but to detect it requires something > like a field-mill JK> It's similar in some ways to a method for detecting magnetic fields JK> used prior to the advent of Hall effect devices. Not sure how it JK> relates to relativity. I think a saturable core can be used to measure a static magnetic field. Early computer magnetic core memories worked like this. Relativity transforms static fields into dynamic fields by adding a velocity component to the measurement. JK> Perhaps it's true that an electric field is simpler create than to JK> detect by direct means. But it isn't really any more difficult than, JK> for example, measuring power by direct means. I think Ben Franklin JK> measured the E field in a Leyden Jar by calibrating the leaf JK> displacement caused by the Coulomb force resulting from the electric JK> field between the two similarly charged surfaces. That Leyden Jar experiment was measuring charges not the E field itself. An E field doesn't require the exchange of charges. I wonder if it is possible to directly measure an E field by the effect of the virtual quanta in its close vicinity? A*s*i*m*o*v ... Quoting one is plagiarism. Quoting many is research. Article: 219659 of rec.radio.amateur.antenna From: "Jeff Dieterle" Subject: Re: Am Antenna Help Date: Wed, 30 Nov 2005 10:27:25 -0500 Message-ID: <11orh6rkdfkqj6a@corp.supernews.com> References: <11oos4qo1fo1dd2@corp.supernews.com> Ya I know, if I move it to right angles the length will shorten to around 40ft. Do you think it would make much difference ? "Allodoxaphobia" wrote in message news:slrndop9if.30qn.bit-bucket@shell.config.com... > On Tue, 29 Nov 2005 10:15:37 -0500, Jeff Dieterle wrote: >> I'm inside an office inside an old brick and steel factory and can get >> very >> little AM reception, only a few of the stations located in the same >> city. I >> ran RG6-U coax to the roof of the factory (appx.100ft) and considered >> buying >> a loop antenna but at this groups suggestion connected the coax to a long >> wire. The stations I'm interested in are Indianapolis 1070kc and Chicago >> 670kc & 1000kc. I installed 200ft of #12ga insulated wire that is >> orientated >> in line with these 2 cities and ..... > ^^^^^^^ > ??????? > > In-line? The wire should be broadside to the desired path of propagation. > > >> ... I can get these stations fine >> in the daytime with a reasonable amount of static but at night the static >> increases severely. Is there anything else I can do to make this a >> better >> antenna. > > You never mention how far away you are from "... Indianapolis 1070kc and > Chicago 670kc & 1000kc." That'll have a LARGE bearing on the day/night > reception question. > > Jonesy > -- > Marvin L Jones | jonz | W3DHJ | linux > Pueblo, Colorado | @ | Jonesy | OS/2 __ > 38.24N 104.55W | config.com | DM78rf | SK Article: 219660 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna reception theory References: Message-ID: Date: Wed, 30 Nov 2005 15:53:50 GMT > I wonder if it is possible to directly measure an E field by the > effect of the virtual quanta in its close vicinity? If the effect of virtual quanta could be measured, would they still be virtual? -- 73, Cecil http://www.qsl.net/w5dxp Article: 219661 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna reception theory Date: Wed, 30 Nov 2005 09:56:52 -0800 Message-ID: References: Asimov wrote: > I think a saturable core can be used to measure a static magnetic > field. Early computer magnetic core memories worked like this. I was referring to the similarity to a rotating coil gaussmeter. I think what you're describing now is something more akin to the fluxgate magnetometer. > Relativity transforms static fields into dynamic fields by adding a > velocity component to the measurement. I see. Is Omni magazine still in print by any chance? > That Leyden Jar experiment was measuring charges not the E field > itself. Leyden jars store charge. As I said before, they produce an indication by relying on the electric field between charged surfaces and the resulting Coulomb force. The more charge stored in the jar, the greater the electric field. Charge, E field, and Coulomb force all being in proportion, the Leyden jar produces a response in proportion to all three. jk Article: 219662 of rec.radio.amateur.antenna From: Bob Nielsen Subject: Re: website about DXpeditions ? Date: Wed, 30 Nov 2005 10:01:29 -0800 Message-ID: References: <438da66c$1@news.vo.lu> On Wed, 30 Nov 2005 14:17:31 +0100, Thierry wrote: > Hi, > > Simple question, > > Is there somewhere on the Internet a website dedicated to the release of > stories about DXpeditions (I think well to ARRL but their text is quite > small), there are CQ and QST but its on paper and not dedicated, but rather > a website covering most of these activities and in anotehr way that simply > listing the date of their QRV (membres, qsl, date, story, rig, etc, etc) ? NG3K's Announced DX Operations page lists DXpeditions and has links to the DXpedition web page, if one exists. 73, Bob N7XY Article: 219663 of rec.radio.amateur.antenna From: Michael Coslo Subject: Re: C. Crane's Twin Ferrite Antenna Date: Wed, 30 Nov 2005 13:20:03 -0500 Message-ID: References: <1l_if.19425$BZ5.1171@newssvr13.news.prodigy.com> <7N9jf.21327$7h7.17117@newssvr21.news.prodigy.com> W. Watson wrote: > Cecil Moore wrote: > >> W. Watson wrote: >> >>> Cecil Moore wrote: >>> >>>> Why do you think that's a radio problem? :-) >>> >>> >>> >>> When I turn the computer off, the radio station noise drops >>> dramatically. It doesn't matter if I use AC or DC. I can detect the >>> large noise change in my car from the garage. >> >> >> >> That sounds like a computer problem, not a radio problem. >> What am I missing? > > Probably nothing. However, I'd be willing to bet that I wouldn't have > this problem if I were 100 miles closer to the radio station. Absolutely. If the station signal is relatively stronger than the computer noise, the computer's RFI will not be so much an issue. Right now, they are about the same strength. Moving the computer will probably help a lot. Just out of curiosity, what is the frequency of the station you are trying to recieve? And while we are at it, is the noise on the radio in just one spot, or is it on pretty much the whole band? - 73 de Mike KB3EIA - Article: 219664 of rec.radio.amateur.antenna From: "Terry" References: <11oos4qo1fo1dd2@corp.supernews.com> <11orh6rkdfkqj6a@corp.supernews.com> Subject: Re: Am Antenna Help Message-ID: Date: Wed, 30 Nov 2005 14:44:01 -0330 "Jeff Dieterle" wrote in message news:11orh6rkdfkqj6a@corp.supernews.com... > Ya I know, if I move it to right angles the length will shorten to around > 40ft. Do you think it would make much difference ? > "Allodoxaphobia" wrote in message > news:slrndop9if.30qn.bit-bucket@shell.config.com... >> On Tue, 29 Nov 2005 10:15:37 -0500, Jeff Dieterle wrote: >>> I'm inside an office inside an old brick and steel factory and can get >>> very >>> little AM reception, only a few of the stations located in the same >>> city. I >>> ran RG6-U coax to the roof of the factory (appx.100ft) and considered >>> buying >>> a loop antenna but at this groups suggestion connected the coax to a >>> long >>> wire. The stations I'm interested in are Indianapolis 1070kc and Chicago >>> 670kc & 1000kc. I installed 200ft of #12ga insulated wire that is >>> orientated >>> in line with these 2 cities and ..... >> ^^^^^^^ >> ??????? >> >> In-line? The wire should be broadside to the desired path of >> propagation. >> >> >>> ... I can get these stations fine >>> in the daytime with a reasonable amount of static but at night the >>> static >>> increases severely. Is there anything else I can do to make this a >>> better >>> antenna. >> >> You never mention how far away you are from "... Indianapolis 1070kc and >> Chicago 670kc & 1000kc." That'll have a LARGE bearing on the day/night >> reception question. >> >> Jonesy >> -- >> Marvin L Jones | jonz | W3DHJ | linux >> Pueblo, Colorado | @ | Jonesy | OS/2 __ >> 38.24N 104.55W | config.com | DM78rf | SK > > One wavelength at a frequency of say 1070 kcs is a little less than 300 metres (approx 1000 feet?). An antenna of either length will be very 'short' compared to the 'wavelengths' involved and will not be close to resonance. e.g. For quarter wave resonance (approx 75 metres or about 250 feet; for 1070 kcs and nearly 400 feet for say 670 kcs ) required. Any 'too short' antenna will be will be badly mismatched (energy loss!) to the impedance of the co-ax. This suggest that some kind of untuned impedance matching transformer, suitable for the frequencies in question, might be used to transfer as much energy as possible to the co-ax transmission line? Seen this done with short 'whip' antenna operating at Broadcast Band/Medium Wave frequencies. Transmission line should also be matched at the receiver end? 100 feet of coax at those frequencies should have low loss? Article: 219665 of rec.radio.amateur.antenna From: K7JEB Subject: Re: C. Crane's Twin Ferrite Antenna Message-ID: References: Date: Wed, 30 Nov 2005 11:50:31 -0700 On Wed, 30 Nov 2005 13:26:37 GMT, "W. Watson" wrote: > W. Watson wrote: > I'll continue to experiment, but so far not > so good. Comments? I would like to relate my experience. As you did, I carefully selected a new computer case and power supply from the stock at , paying careful attention to the FCC logo on the power supply. After moving the mother board over and turning it on, it completely wiped out reception of the local 5kW station on 550 kHz. Fortunately, I had picked up a couple of surplus Corcom line filters (Model # 10ESK7)at a local hamfest three years earlier (it pays to collect junk). I spliced it into the computer power cord and it cured the problem completely. I don't have any experience with the Radio Shack line filter (Catalog # 15-1111), but it looks like it might do the job for you. 73, Jim, K7JEB Article: 219666 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Mobile 2m/70cm antenna Date: Wed, 30 Nov 2005 11:24:47 -0800 Message-ID: <11orv408qms0pfd@corp.supernews.com> I recently bought a Larsen 2m/70cm NMO mag-mount mobile antenna for my truck. It's the first time I've ever owned a mobile antenna because I don't do that much driving (I work from home). I don't have a mobile radio in the truck, I just have an HT. What I wanted to do was hook up my Icom W32A to the mobile antenna when I'm in the truck. So, I put the mag-mount on the middle of the pickup roof and started driving. I compared the mobile Larsen antenna to my Diamond RH77CA HT antenna. What I noticed is that with the Diamond antenna on the HT inside the truck, it consistently pulls in more signal (on both bands) than the Larsen mobile outside the truck. The Diamond antenna is of course an HT antenna, so it's optimized for HT use. Is this normal behavior for a mobile antenna hooked up to an HT? If it's not normal, then this is not that great of a mobile antenna. Rod KI7CQ Article: 219667 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: WorldRadio Magazine Article Date: Wed, 30 Nov 2005 11:34:50 -0800 Message-ID: <11orvmp8ac1idbd@corp.supernews.com> References: Nice article, Cecil. Rod KI7CQ Article: 219668 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: Mobile 2m/70cm antenna Date: Wed, 30 Nov 2005 11:44:21 -0800 Message-ID: <11os08jsfscp90f@corp.supernews.com> References: <11orv408qms0pfd@corp.supernews.com> I stuck the mag mount on the roof and ran the coax in through the sliding window on the back of the cab, so as not to pinch the cable. I had to use a UHF to BNC adapter to hook the cable to the HT. I just checked and I don't see any pinched places in the coax. Rod Article: 219669 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: WorldRadio Magazine Article References: <11orvmp8ac1idbd@corp.supernews.com> Message-ID: Date: Wed, 30 Nov 2005 19:54:17 GMT Rod Maupin wrote: > Nice article, Cecil. Thanks Rod. I expect to post part II to my web page at the end of Dec. and part III at the end of Jan. The real meat is in part II. The amazingly useful stuff is in part III where the special-case (matched case) is actually the norm for amateur radio operators. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219670 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Mobile 2m/70cm antenna References: <11orv408qms0pfd@corp.supernews.com> <11os08jsfscp90f@corp.supernews.com> Message-ID: Date: Wed, 30 Nov 2005 19:55:24 GMT Rod Maupin wrote: > I just checked and I don't see any pinched places in the coax. Hang an MFJ-259B or 269 on it and find out what's wrong. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219671 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <0k0so1hqr95fd08kelufhnn07a3mkk72s9@4ax.com> References: <73Kif.34189$6e1.12840@newssvr14.news.prodigy.com> <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> <3fkpo1578sa6nejfr47umsq10d970jqjkc@4ax.com> Date: Wed, 30 Nov 2005 20:06:45 GMT On Wed, 30 Nov 2005 17:08:27 GMT, Cecil Moore wrote: >Owen, it's pretty obvious that you were manufactured with a >lower tolerance (+/- 0.1%) than I was (+/- 20%). :-) Over on Perhaps... Now, I think you have told us over several articles that you are using an SGC500 into a 30 ohm load on 7.15MHz. That 30 ohm load is a result of feeding a dipole with 90' of ladderline, which I estimate has 0.9dB of loss under those circumstances. If your transmitter was delivering 500W to the feedline, about 100W is lost in the feeder. Do you know how much power your amplifier delivers to the feedline? It is likely that with a load VSWR of 1.7 it may have reduced output, it is also possible that it is delivering even more than 500W to the low Z load. Owen -- Article: 219672 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: Mobile 2m/70cm antenna Date: Wed, 30 Nov 2005 12:26:18 -0800 Message-ID: <11os2n8psrgmq3f@corp.supernews.com> References: <11orv408qms0pfd@corp.supernews.com> <11os08jsfscp90f@corp.supernews.com> I'll have to get an MFJ meter and check it out. I've been putting off buying one anyway. Seems like they would be nice to have. Rod Article: 219673 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Wed, 30 Nov 2005 21:01:57 GMT "Cecil Moore" bravely wrote to "All" (30 Nov 05 15:53:50) --- on the heady topic of "Re: Antenna reception theory" CM> From: Cecil Moore CM> Xref: core-easynews rec.radio.amateur.antenna:220639 > I wonder if it is possible to directly measure an E field by the > effect of the virtual quanta in its close vicinity? CM> If the effect of virtual quanta could be measured, CM> would they still be virtual? Yes, there is a measurable force. The Casimir Effect is the action virtual particles have on a pair of parallel metal plates, pushing them together (only by an extremely tiny amount). This is because more virtual particles are created outside the plates than between them. A*s*i*m*o*v ... There are subliminal messages in Campbell's Alphabet Soup! Article: 219674 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: Antenna reception theory Message-ID: References: Date: Wed, 30 Nov 2005 21:02:01 GMT "Jim Kelley" bravely wrote to "All" (30 Nov 05 09:56:52) --- on the heady topic of "Re: Antenna reception theory" JK> From: Jim Kelley JK> Xref: core-easynews rec.radio.amateur.antenna:220642 JK> Asimov wrote: > I think a saturable core can be used to measure a static magnetic > field. Early computer magnetic core memories worked like this. JK> I was referring to the similarity to a rotating coil gaussmeter. I JK> think what you're describing now is something more akin to the JK> fluxgate magnetometer. > Relativity transforms static fields into dynamic fields by adding a > velocity component to the measurement. JK> I see. Is Omni magazine still in print by any chance? Omni is not my cup of tea. Much too glossy for me! What I meant was if the person taking the measurement is in motion relative to the field, then the field will seem to be dynamic. A*s*i*m*o*v ... This is an SOS call from the mining ship Red Dwarf Article: 219675 of rec.radio.amateur.antenna From: "Rod Maupin" Subject: Re: Mobile 2m/70cm antenna Date: Wed, 30 Nov 2005 14:04:14 -0800 Message-ID: <11os8et3cm0o14c@corp.supernews.com> References: <11orv408qms0pfd@corp.supernews.com> <11os08jsfscp90f@corp.supernews.com> <11os2n8psrgmq3f@corp.supernews.com> Thanks for the offer Amos, but I live in WA state. Too far of a drive for you. I actually have my radio club meeting tonight. So, I'll have to ask someone. The main thing is that you told me it wasn't normal, which makes me feel better. Rod Article: 219676 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: <1c8so1tpnnqmn2at06s2djk2k240bco793@4ax.com> References: <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> <3fkpo1578sa6nejfr47umsq10d970jqjkc@4ax.com> <0k0so1hqr95fd08kelufhnn07a3mkk72s9@4ax.com> Date: Wed, 30 Nov 2005 22:14:55 GMT On Wed, 30 Nov 2005 21:35:32 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Now, I think you have told us over several articles that you are using >> an SGC500 into a 30 ohm load on 7.15MHz. > >Now please be a gentleman and please don't go putting words in my mouth. Well, there was some uncertainty, and it is why I opened with "I think...". >Here a quote of my exact words: > >"Speaking of indirect measurements - let's say the feedline Z0 is 380 >ohms with a VF of 0.9 and a length of 90 ft. The measured resistance >at the current maximum point is 30 ohms on 7.15 MHz." > >Clearly, "let's say", is a hypothetical postulate. I freely admit that >I pulled those values out of thin air. Going back to my web page reveals >that the feedpoint impedance on 40m for my 130 ft. dipole was really 38 >ohms. Nonetheless, I can still make my point assuming the 30 ohm value >which would have been perfectly acceptable to me. > >> If your transmitter was delivering 500W to the feedline, about 100W is >> lost in the feeder. > >With a 1.7:1 SWR???? Maybe you should reprogram your calculator to take >the square root???? The ratio of Pref/Pfor for an SWR of 1.7:1 is 0.067. >Methinks you might be using the voltage reflection coefficient? Ok, I saw your later post where you have note that you were on the wrong track here. > >500(0.067) is 34 watts, not 100 watts. The SGC-500 laughes at 34 watts >reflected. (I swear that is true. I have heard it laughing to itself in >the wee hours during a contest.) Seriously, that amp is not known as >"The Brick" just because it looks like a brick. > >> Do you know how much power your amplifier delivers to the feedline? It >> is likely that with a load VSWR of 1.7 it may have reduced output, it >> is also possible that it is delivering even more than 500W to the low >> Z load. > >An SWR of 1.7:1 is nothing to worry about unless you think the percentage >power reflected is the same as the percentage voltage reflected. Don't feel >bad, many others have made that same mistake. Most people are programmed not >to think within a power/energy context and it gets them into trouble with >such concepts as "reflected power just sloshes around from side-to-side" and >"gobbledegook" applied to any attempt to track energy in a transmision line. > >The SGC-500 is speced to tolerate an SWR of 6:1. That means that it can >dissipate more than half of its output power and keep on ticking. I >don't recommend allowing that to happen but that spec is why I don't worry >at all about reflected power unless the SWR is in excess of 2:1. Lets leave that issue alone. > >If we keep arguing, one of us is bound to make a mistake that the other >catches. I would guess that your above mistake bothers you a lot more >than it bothers me. :-) Well, I think we are agreed that you made a mistake in identifying a mistake, if I am not mistaken! No, back on track, I thought you might have measured forward and reflected power at the amplifier output on the 30 ohm load, to deduce the net forward power, then by allowing for the line loss, you would have the net power at the feedpoint (most of which will be radiated in some direction or another). One could then calculate the performance of the feed configuration compared to what would be delivered to an ideal nominal load with no feed loss. The whole excercise goes nowhere, because it seems that the 30 ohms scenario is "hypothetical". Owen -- Article: 219677 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: WorldRadio Magazine Article Message-ID: <7xpjf.141728$yS6.37907@clgrps12> Date: Wed, 30 Nov 2005 22:16:35 GMT >> Part 1 of my WorldRadio Oct. 2005 energy analysis article is >> now available on my web page in Microsoft Word .doc format. > > For those of you not running Microsoft Word, the article is > available in Adobe .pdf format. Please excuse the commercial > at the bottom of the pages. (I'm too cheap to buy the full > version of PDF4U.) :-) > -- > 73, Cecil http://www.qsl.net/w5dxp/energy.pdf Thanks Cecil, very interesting. Will look forward to reading your other articles. Regards, Frank Article: 219678 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: SWR again. References: <97Nif.27749$tV6.26014@newssvr27.news.prodigy.net> <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> <3fkpo1578sa6nejfr47umsq10d970jqjkc@4ax.com> <0k0so1hqr95fd08kelufhnn07a3mkk72s9@4ax.com> <1c8so1tpnnqmn2at06s2djk2k240bco793@4ax.com> Message-ID: Date: Wed, 30 Nov 2005 23:42:33 GMT Owen Duffy wrote: > Well, I think we are agreed that you made a mistake in identifying a > mistake, if I am not mistaken! Your original mistake was in making a posting that caused me to misunderstand. :-) Your loss calculator gives 0.762 dB loss for 90 feet of Wireman #445 with an SWR of 12.7:1 on 7.15 MHz. > The whole excercise goes nowhere, because it seems that the 30 ohms > scenario is "hypothetical". I knew it was thirty-something ohms so I said "30". It was actually 38 ohms indicating an SWR at the source of 1.3:1. That's acceptable losses for me. If I used an antenna tuner to achieve a 1:1 match, it would probably be a wash. Which is probably a good question. At what SWR should one install an antenna tuner? My IC-706 seems perfectly happy at 2:1. -- 73, Cecil http://www.qsl.net/w5dxp Article: 219679 of rec.radio.amateur.antenna From: ml Subject: Re: vert dipole vs vert References: Message-ID: Date: Wed, 30 Nov 2005 23:51:48 GMT In article , dt@dt.prohosting.com (David B. Thomas) wrote: > >>>>> "ml" == ml writes: > > ml> i was trying to figure loosly in real world case what the > ml> difference would be (generally speaking) between say a > ml> verticle all band commercial antenna on my roof (of my tall > ml> apt building) i'd naturally install it's radial kit > > ml> vs > > ml> a equal all band (yeah i know it'd be tall) virticle dipole > ml> (tweeked w/a tuner sgc at feedpoint > > The commercial vertical probably uses traps or other means to act like > a quarter wave ground plane on all bands. This would be roughly > equivalent, performance-wise, to a separate vertical dipole cut for > each band. > > The issue with using the tuner is that a tall dipole used on a high > frequency will throw a lot of energy up at high angles. On 15 and 10 > meters, you'd probably rather have a nice low angle pattern. Then > again, when those bands are open, you can usually afford to have an > inefficient antenna as propagation tends to be excellent. > > So, if you're looking to put up something fast and cheap, the dipole > and tuner idea can certainly work. If you do that, try to keep the > feed line perpendicular as long as you can before it drops down. > > David > N5IZU thank you very much david for your help, i was sorta thinking a commercial one might radiate out more that way and was double checking to see what i might have missed appreciate the advice tnx Article: 219680 of rec.radio.amateur.antenna From: "Old Ed" References: <4vOdnaymcczQzRbenZ2dnUVZ_sudnZ2d@comcast.com> Subject: Re: Beginners Antenna Quest's (for listening only) Message-ID: <4Trjf.3890$A23.1364@newsread2.news.pas.earthlink.net> Date: Thu, 01 Dec 2005 00:56:32 GMT Hi "B.," I'll take a stab at responding to your questions. See below... "Robert11" wrote in message news:4vOdnaymcczQzRbenZ2dnUVZ_sudnZ2d@comcast.com... > Hello: > > Really new at this, and not really savy on antennas at all. > Trying to learn, but sure is a complicated subject. > > Do sw listening only, just about anywhere below 30 MHz. No preferred > direction. No transmitting. > > Presently have a "random length" horiz. wire running around the inside > of my attic. Live in a typical New England colonial. > Goes around the 4 walls, and is stapled every few feet to a wooden roof > support joist. Probably about 40' x 25' x40' x 25' approximately. > > Not connected at the end, so I guess can't be considered a true loop. > > Questions: > > a. Does stapling to the wood degrade performance ? (wire is insulated) > No, the staples shouldn't hurt. > b. Does the roof degrade performance ? How about when wet ? > A wet roof is somewhat lossy, so it certainly won't help. But an attic antenna can still work for you, as it has for others. > c. Would you expect considerably better performance if this exact > same configuration was outdoors, at the same height ? > Yes, outdoors should be somewhat better. It might also allow a better configuration. > d. Would it be better if it were soldered back at the beginning, thus > making a true horiz loop (with about a 10 foot vertical run to the > receiver? Why ? > If you're talking about creating a circular monopole, no that would not be a good idea. It would probably have much the same effect as cutting off the far half of your wire. > And I guess i should ask: For a single straight random length wire, > is the most sensitivity perpendicular to the wire direction ? > (assuming20 feet off theground, and perhaps 60 feet in length) > It's more complicated than that, and depends on frequency. Don't worry about directionality unless you plan to build a sophisticated directional antenna. > Would you expect this to be much better than the indoor configuration > I now have ? Why ? > It's not clear what "this" refers to. > Is there a good pix on the web showing the lobes for this configuration; > looked, but couldn't find a simple enough one for me to really understand. > Again, it's not clear what "this" is. > Much thanks; appreciate the help, > B. > > Article: 219681 of rec.radio.amateur.antenna Date: Wed, 30 Nov 2005 21:44:30 -0600 From: Tom Ring Subject: Re: SWR again. References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> Message-ID: <438e719e$0$47677$39cecf19@news.twtelecom.net> Reg Edwards wrote: > Gerry, > > The load is the antenna - about which the SWR meter knows absolutely > nothing. All the the meter has to work with is the input impedance of > the tuner or the transmission line. > > Line input Z = R+jX and to aggravate matters the meter discards all > information about X. > ---- > Reg. > > The load that counts is what the transmitter sees. Which is what his instrument measures. tom K0TAR Article: 219682 of rec.radio.amateur.antenna Date: Wed, 30 Nov 2005 22:00:03 -0600 From: Tom Ring Subject: Re: Stacking Satellite VHF and UHF F9FT Antennas References: <1133311300.421664.127270@g44g2000cwa.googlegroups.com> Message-ID: <438e7559$0$3761$39cecf19@news.twtelecom.net> alain@alain.it wrote: > Hello all, > > I actually own a 2x9 VHF and a 2x19 UHF by F9FT (Tonna). > Since I need better performance (especially on VHF) for LEO operations > I was thinking about stacking another antenna identical to the one I > already have. > The suggested stacking distance is 2.77 m. Since I am doing this > upgrade I tought about stacking another UHF antenna too so that I would > have an horizontal mast 3 meters long, with the VHF yagis at the ends > and the UHF yagis in the middle. > > I have some questions: > 1) Will the UHF yagis create troubles to the VHF since they are in the > middle? No. > 2) What kind of real performance increase will I experience on VHF? If the spacing is correct you will see roughly 3dB. > 3) Can I couple the vertical elements with a coupler and the horizontal > elements with another coupler and then apply a RCHP/LCHP coupling > harness like I would normally do on a single antenna? This doesn't match what you are speaking of in questions 1 and 2. You cannot have the gain you desire and have the second set of antennas differently polarized. That is a different configuration which requires a feed that gives you circular polarization. tom K0TAR > Thanks > > Alain De Carolis > iz6byy ww3ww > Article: 219683 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR again. Message-ID: References: <1efpo153ju7lgkn5hai1otaifo83rqi3u0@4ax.com> <3fkpo1578sa6nejfr47umsq10d970jqjkc@4ax.com> <0k0so1hqr95fd08kelufhnn07a3mkk72s9@4ax.com> <1c8so1tpnnqmn2at06s2djk2k240bco793@4ax.com> Date: Thu, 01 Dec 2005 04:07:04 GMT On Wed, 30 Nov 2005 23:42:33 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Well, I think we are agreed that you made a mistake in identifying a >> mistake, if I am not mistaken! > >Your original mistake was in making a posting that caused me to >misunderstand. :-) Your loss calculator gives 0.762 dB loss for >90 feet of Wireman #445 with an SWR of 12.7:1 on 7.15 MHz. Now, you're trying to trick me... did you mean Wireman 554? It does show 0.76dB for 90' of 554 with a 30+j0 input Z at 7.15MHz. The 0.9dB stated earlier was (as stated) for 552 which had a Zo closer to your 380 ohms, whereas 554 is 360 ohms. > >> The whole excercise goes nowhere, because it seems that the 30 ohms >> scenario is "hypothetical". > >I knew it was thirty-something ohms so I said "30". It was >actually 38 ohms indicating an SWR at the source of 1.3:1. >That's acceptable losses for me. If I used an antenna tuner >to achieve a 1:1 match, it would probably be a wash. > >Which is probably a good question. At what SWR should one >install an antenna tuner? My IC-706 seems perfectly >happy at 2:1. Given that some radios (including the IC706-IIG) reduce drive power at high VSWR as a protection mechanism, you may want to install an ATU to develop full power output. My recollection is that the power output of the IC706-IIG is significantly down at VSWR=2, but it probably also depends on the actual load impedance. A likely scenario could be that the radio only develops 50W of output, and only 40W makes it to the feedpoint (assuming 1dB feed loss). The ATU might raise that to 100W of output, less tuner loss and feed loss giving 75 to 80W at the feedpoint. Mere fraction of an S point... but if you have a 100W transmitter, might as well use it, and besides, the technical challenge of achieving that goal and measuring the achievement might be part of what amateur radio is about. Owen -- Article: 219684 of rec.radio.amateur.antenna From: K7JEB Subject: Re: C. Crane's Twin Ferrite Antenna Message-ID: <84vso1pf1ltnr7trci1f8iccoohvgm1h4e@4ax.com> References: Date: Wed, 30 Nov 2005 21:42:18 -0700 On Thu, 01 Dec 2005 00:20:41 GMT, "W. Watson" wrote: >> I don't have any experience with the Radio >> Shack line filter (Catalog # 15-1111), but it >> looks like it might do the job for you. > The RShk ferrite rectangles didn't help. > Interesting about the Corcom filters. I'm going > down to a radio shop on Friday, HSC in Sacramento. > Maybe I can find something there. Take a look at the 15-1111 on www.radioshack.com. It is NOT a clamp-on ferrite choke, but rather a filter like the Corcom. I just thought it might be a bit more accessible. But if you can find a 10-amp Corcom, go for it! (Actually, a 3-amp model should work). Anyway, your problem is definitely solvable, and for relatively little $$$. Jim, K7JEB Article: 219685 of rec.radio.amateur.antenna Date: Wed, 30 Nov 2005 21:46:23 -0700 From: BKR Subject: Re: C. Crane's Twin Ferrite Antenna References: Message-ID: <438e802d@nntp.zianet.com> Computers and computer components are regulated by the FCC. They MUST NOT cause interferance to licenced radio services. (like the radio stations you are trying to tune in.) Make that clear to the vendor you got the power supply from! KD5RPO W. Watson wrote: > Michael Coslo wrote: > >> W. Watson wrote: >> >>> I bought this antenna on a 30 day trial, and just got it about 12 >>> hours ago. So far I'm not at all impressed. I live about 150 miles >>> from an AM station, at 810, in the SF/SJ Bay Area, which has a >>> marginal signal, but usually listenable. Putting a new PSU in a PC >>> about a month ago increased the noise in AM radios 70-100' from the >>> PC to an almost unacceptable level. I had hoped the antenna would >>> boost the signal enough to knock down the noise. There are times when >>> I can get a good signal from the station, but certainly less >>> frequently than before. >> >> >> >> Any rf noise put out by the computer ps is going to be picked up >> by your antenna as well as the radio station you are trying to hear. >> So a better antenna (if your new one is indeed better) wil just pick >> up stronger power supply noise. It's moslty a null situation. >> >> What you need to do is get that power supply fixed or replaced >> >> - 73 de Mike KB3EIA - >> > I think the only solutions to the PSU problem is to buy a much better > one. As I mention above, that's probably a losing proposition. I doubt > after 6 weeks they would take it back. It might be worth a try though. > Note my comment above to someone a few moments ago that this seems to be > a household circuit dependent problem. Another PC in the same room works > fine until I plug it into the socket that I first noticed the problem. > > > Article: 219686 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Thu, 1 Dec 2005 06:46:58 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <438e719e$0$47677$39cecf19@news.twtelecom.net> > The load that counts is what the transmitter sees. Which is what his > instrument measures. > > tom > K0TAR ======================================== I fully agree the transmitter load is what the transmitter sees. But his meter does not measure it. His meter simply tells him whether or not its resistance is 50 ohms. Which is all he wants to know anyway. ---- Reg, G4FGQ Article: 219687 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: SWR again. Date: Thu, 1 Dec 2005 07:52:23 +0000 (UTC) Message-ID: References: <1133173268.768403.217280@f14g2000cwb.googlegroups.com> <438e719e$0$47677$39cecf19@news.twtelecom.net> "Richard Clark" wrote > > Jerry has a slotted line - described here in loving detail some time > ago. It and the meter so attached is perfectly capable of measuring > all the factors stated. > > >Which is all he wants to know anyway. > > which is an assumption (or a forced argument, take your pick) as he > has already reconciled any mis-understandings. ======================================== Richard, please explain what purpose is served by the above message. Am I missing something? --- Reg. Article: 219688 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: using a model Date: Thu, 01 Dec 2005 00:26:50 -0800 Message-ID: <11otcudpfmj6096@corp.supernews.com> References: To make an exact scale model of an antenna, you not only have to scale all physical dimensions, but also the conductivity - the model's conductivity has to be freal/fmodel times the real conductivity. (Dielectric constant and permeability remain the same in the model as in the real antenna.) So in order to test the efficiency of various ground systems, you'll have to bury radial wires in model "dirt" which is several times more conductive than real dirt, while having the same dielectric constant as real dirt. (For example, if the real antenna is for 7 MHz, the model "dirt" will have to be about 20 times as conductive as real dirt but with the same dielectric constant.) Technically, you also have to do the same with the antenna conductor, but hopefully the conductor loss will be small enough that you won't have to worry about it. If the loading coil loss is significant, you'll have to construct a model coil with a scaled inductance but the same resistance (that is, the same Q) as the real one. The pattern of a vertical antenna is heavily influenced by the conductivity of the ground extending several wavelengths from the antenna. So if you want to realistically evaluate the pattern, you'll need to extend your highly conductive model "dirt" to at least that distance. Then there's the problem of measurement. Nearly everyone seriously overestimates his ability to accurately measure RF quantities such as impedance and field strength at HF. It's even more difficult at 2 meters. If you even want to attempt this, you should begin with models of several antennas of known characteristics, such as a quarter wavelength vertical and a resonant near-quarter wave vertical. See how closely your measurements agree with theoretical results. If and when you can get close agreement, then you have some chance on trusting measurements of other antennas. But even then it's not a certainty. Those are some of the pitfalls. Roy Lewallen, W7EL dansawyeror wrote: > All, > > I have been trying to determine the operation of a loaded vertical on 75 > meters and over a less then perfect ground. It is inconvenient to > measure and change do its location. > > After many attempts to solve this I have struck upon a solution to 'get > close'. I have decided to build a model that works on 2 meters. This > will be small enough to construct in the shack and to experiment with > various 'grounds'. > > What are the pit falls in doing this? > > Thanks Dan kb0qil Article: 219689 of rec.radio.amateur.antenna From: Phil Wheeler Subject: Re: C. Crane's Twin Ferrite Antenna References: <438e802d@nntp.zianet.com> Message-ID: <8Kzjf.84363$QM5.38523@tornado.socal.rr.com> Date: Thu, 01 Dec 2005 09:53:08 GMT BKR wrote: > Computers and computer components are regulated by the FCC. > They MUST NOT cause interferance to licenced radio services. > (like the radio stations you are trying to tune in.) > Make that clear to the vendor you got the power supply from! > Interesting thought but impractical. It could be the installation (e.g., grounding) vs. the supply itself. Event if the PSU itself, proving it would be a chore.