Article: 218814 of rec.radio.amateur.antenna Subject: Re: antenna wire cleanup question From: Ed References: <3Cb7f.3302$UF4.2370@fed1read02> Message-ID: Date: Tue, 25 Oct 2005 00:50:14 GMT "k6zsr" wrote in news:3Cb7f.3302$UF4.2370@fed1read02: > After 47 years of hamming, I found that this is the best way to clean > corroded stranded #14 copper antenna wire ( may also work on #12) > especially if you experience another "Rita" > > 1.) Make yourself a strong MargaRITA drink using ONLY Hornitos > Tequilla. 2.) After you finish drinking the MargaRITA, dip the end of > your antenna wire into the residue at the bottom of the glass. > 3.) Using the lemon slice, carefully wipe the end of your antenna wire > clean. > 4.) Repeat 1 through 3 four times. Hmmm... repeate all steps four times? I expect after drinking five Margaritas I won't even be able to find my way out of the room..... Ed K7AAT Article: 218815 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Tue, 25 Oct 2005 12:22:34 +0000 (UTC) Message-ID: References: <7l2ml1p4e9mjunf4ho30hd6uoj4e25756q@4ax.com> <1130172617.761487.141900@g14g2000cwa.googlegroups.com> <1130198226.999340.13750@g49g2000cwa.googlegroups.com> Stranded, layer-wound wire, even when strands are individually insulated, behaves similar to solid wire of slightly smaller diameter. The strands in true Litz are WOVEN such that every strand spends the same length in inside and outside and intermediate layers of the cable. Current is then more uniformly distributed throughout the conductor's cross-section. The diameter of an individal strand should not be greater than about about twice skin depth. Otherwise effectiveness decreases. Thus, at high frequences where skin depth is very small, very fine wire must be used. There are practical and economic limits to the fineness of drawn copper wire. There is little to be gained by using ordinary Litz above 3 or 4 MHz. At high frequencies with small coils of few turns, such as receiving coils, tank and loading coils, it is far more economic to increase Q just by increasing the diameter of solid copper wire. Litz is at its best from VLF to IF and MF. ---- Reg. Article: 218816 of rec.radio.amateur.antenna Message-ID: <3130303038373835435C95DA15@zetnet.co.uk> Date: Mon, 24 Oct 2005 08:05:46 +0100 From: Dave Piggin Subject: Re: antenna wire cleanup question References: Got some dirty, corroded stranded #14 copper antenna wire I need to solder/splice. Ever tried using Coke/Pepsi. Dont laugh, try putting an old dime or cent in it for a day or so and see the results. Geeezzzzzzzzz the things we drink today!! Or try cutting it back a tad or two to new wire, you shouldn't notice too much diffrence. -- Amateur Radio Call Sign M1BTI, Located in Manchester England. Locator square IO83TK Chairman Of Trafford Radio Club. Club Call Signs G0TRG & M1BBP Located at Umist, University Of Manchester Institute For Science And Technology Share What You Know, Learn What You Dont. Article: 218817 of rec.radio.amateur.antenna From: "johan aeq" References: Subject: Re: antenna wire cleanup question Date: Tue, 25 Oct 2005 22:31:25 +0200 Message-ID: <3c017$435e97c6$52ad139c$30225@news.versatel.nl> maybe this might help too.. http://j-walk.com/other/wifispray/ "RB" schreef in bericht news:LjS6f.2672$NJ.431@bignews7.bellsouth.net... > Got some dirty, corroded stranded #14 copper antenna wire I need to > solder/splice. Limb fell across my antenna during Rita. I need to clean > off the ends before soldering. What common household product(s) can I put > the ends in overnite to get 'em shiny and ready to solder? > > Article: 218818 of rec.radio.amateur.antenna From: "RB" Subject: antenna lengths Message-ID: Date: Tue, 25 Oct 2005 16:05:08 -0500 There are some commonly occurring lengths for multi-band dipoles. I see 105', 135', and 140'. Is 140' preferred over 135'? If so, what is the benefit of going from 135' to 140'? Just curious. Article: 218819 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: antenna lengths Message-ID: References: Date: Tue, 25 Oct 2005 22:05:38 GMT On Tue, 25 Oct 2005 21:40:09 GMT, Cecil Moore wrote: >That's about a 3.5% difference. You get just about that much difference >between insulated and uninsulated wire. That much difference in length Cecil, do you have theoretical or experimental support for the inference that insulated vs uninsulated wire will be different in length by around 3.5%? What thickness wire / insulation? Owen -- Article: 218820 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: antenna lengths Date: Wed, 26 Oct 2005 00:15:11 +0000 (UTC) Message-ID: References: > do you have theoretical or experimental support for the > inference that insulated vs uninsulated wire will be different in > length by around 3.5%? What thickness wire / insulation? > > Owen ========================================= To calculate change in velocity due to plastic PVC insulation we need to know :- Wire diameter = d Diameter over insulation = D Height of wire above ground = H Permittivity of insulating material = K First calculate capacitance of bare wire to ground. Then calculate capacitance of insulated wire to ground. Velocity Factor = SquareRoot of their ratio. Neither Terman's nor Kraus' Bibles will mention the following formulae. So you'll just have to take my word for it. Velocity Factor = SquareRoot( ( A + B ) / C ) Where - A = K * Ln( 4 * H / D ) B = Ln( D / d ) C = K * Ln( 4 * H / d ) Example : Bare wire diameter = 1.6 mm = 14 awg. Diameter over insulation = 2.6 mm. Height above ground = 10 metres = 33 feet. Permittivity of insulation = 3.5 Velocity factor = 0.983 Or a decrease in resonant frequency of 1.7 percent which can nearly always be forgotten about. The electrical effect of the enamel on magnet wire is entirely negligible. But it does protect the wire from atmospheric pollution. ---- Reg. Article: 218821 of rec.radio.amateur.antenna From: "Frank's" References: Subject: Re: antenna lengths Message-ID: Date: Wed, 26 Oct 2005 01:30:24 GMT "RB" wrote in message news:p4x7f.8913$wG.2612@bignews4.bellsouth.net... > There are some commonly occurring lengths for multi-band dipoles. I see > 105', 135', and 140'. Is 140' preferred over 135'? If so, what is the > benefit of going from 135' to 140'? Just curious. Read the following: http://members.dslextreme.com/users/w6wqc/antenna.html The data on antenna efficiency is a misinterpretation of the NEC output file. It refers only to copper losses, and does not include ground losses. The discussion that "The length of an antenna wire is irrelevant" is the key point made. 73, Frank Article: 218822 of rec.radio.amateur.antenna From: "Krzysztof" Subject: Re: antenna lengths Date: Wed, 26 Oct 2005 12:55:36 +0200 Message-ID: References: > There are some commonly occurring lengths for multi-band dipoles. I see > 105', 135', and 140'. Is 140' preferred over 135'? If so, what is the > benefit of going from 135' to 140'? Just curious. Pse look at the web: http://www.qsl.net/aa1ll/cfwire.htm Depending on your location (length of the feeder and free space for the dipole) consider Region 1, 3 or G5RV Region. 73 Chris SP7ICE Article: 218823 of rec.radio.amateur.antenna From: "Krzysztof" Subject: Re: antenna lengths Date: Wed, 26 Oct 2005 12:57:02 +0200 Message-ID: References: > There are some commonly occurring lengths for multi-band dipoles. I see > 105', 135', and 140'. Is 140' preferred over 135'? If so, what is the > benefit of going from 135' to 140'? Just curious. Pse look at the web: http://www.qsl.net/aa1ll/cfwire.htm Depending on your location (length of the feeder and free space for the dipole) consider Region 1, 3 or G5RV Region. 73 Chris SP7ICE Article: 218824 of rec.radio.amateur.antenna From: "John N9JG" Subject: Twisted antenna farm Date: Wed, 26 Oct 2005 08:37:29 -0500 Message-ID: Antenna farm turned to junk. http://s47.yousendit.com/d.aspx?id=1J4BL8XN5MT2434J4UB0NHYAB6 Article: 218825 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: antenna lengths References: Message-ID: Date: Wed, 26 Oct 2005 14:19:57 GMT Owen Duffy wrote: > Cecil, do you have theoretical or experimental support for the > inference that insulated vs uninsulated wire will be different in > length by around 3.5%? What thickness wire / insulation? Owen, that info came from Roy, W7EL, who built it into the latest version of EZNEC. It has to do with the VF of insulated wire Vs uninsulated wire which affects wire antennas as well as transmission lines. I discovered it for myself when I was building vertical loop antennas many years ago. The equation 1005/f wasn't even close using insulated wire. For instance, my 130 foot bare copper wire dipole is resonant at 3.633 MHz according to EZNEC. Adding 0.05 inch of PE insulation drops the resonant frequency to 3.526 MHz, about a 3% drop according to EZNEC. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218826 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: A few Helical Antenna question Message-ID: Date: Wed, 26 Oct 2005 12:07:11 -0500 I am reading the 19th edition of the ARRL Antenna Book. I am unclear which polarization to use if I want 2 Helical antennas to talk to each other. In the book it says, ". . . when two stations use helical antennas over a non reflective path, both must use antennas with the same polarization sense.." I find this could be interpreted in different ways and is not clear at all. It seems logical to me that if both antennas had the same polarization that when they faced each other they two helices would be in opposite directions and that would seem to be bad. Am I right? It says the circumference can be between 1.33 wavelengths and .75 wavelengths. From the gain formula it would seem that the 1.33 figure would give the most gain for a given length of the antenna. Other than mechanical considerations is there any reason I wouldn't want to use the 1.33 number? Finally, I may have missed it, but I didn't see anything that indicated how large of a wire or tube I should use for the helix. I am guessing this is just a mater of how much power I plan on feeding it with? PS I would like to build 2 of these one is for 2.4ghz wireless network and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz version will likely never see more than 100 mW but could see as much as 1 watt. The 432 mhz version could see as much as 1000 watts, but if I did that it would be to an array of 4 of them so I guess each one would only see 250 watts? -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218827 of rec.radio.amateur.antenna From: "Asimov" Subject: A few Helical Antenna question Message-ID: References: Date: Wed, 26 Oct 2005 22:11:03 GMT "Chris W" bravely wrote to "All" (26 Oct 05 12:07:11) --- on the heady topic of "A few Helical Antenna question" CW> From: Chris W <1qazse4@cox.net> CW> Xref: core-easynews rec.radio.amateur.antenna:219311 CW> I am reading the 19th edition of the ARRL Antenna Book. I am unclear CW> which polarization to use if I want 2 Helical antennas to talk to each CW> other. In the book it says, ". . . when two stations use helical CW> antennas over a non reflective path, both must use antennas with the CW> same polarization sense.." I find this could be interpreted in CW> different ways and is not clear at all. It seems logical to me that CW> if both antennas had the same polarization that when they faced each CW> other they two helices would be in opposite directions and that would CW> seem to be bad. Am I right? "Same polarization sense" means with respect to the traveling wavefront. When the transmitting antenna is nose to nose with the receiving antenna, the combination will corkscrew in one sense only. A*s*i*m*o*v ... "Losing my virginity was a career movement." -- Madonna Article: 218828 of rec.radio.amateur.antenna From: "Jerry Martes" References: Subject: Re: A few Helical Antenna question Message-ID: Date: Wed, 26 Oct 2005 22:45:11 GMT "Joe McElvenney" wrote in message news:u3hvl11t2tdbsch0eam6uqq1n4jhbc2dii@4ax.com... > Hi, > >>other. In the book it says, ". . . when two stations use helical >>antennas over a non reflective path, both must use antennas with the >>same polarization sense.." I find this could be interpreted in >>different ways and is not clear at all. It seems logical to me that if >>both antennas had the same polarization that when they faced each other >>they two helices would be in opposite directions and that would seem to >>be bad. Am I right? > > On your first point, imagine you've constructed a long, long > helix that starts at your location and travels all the way to the > other station. It is logical that a wave launched by you would > then travel unimpeded along it to the far location. Now cut the > helix in the middle and turn one end around. What you will then > see is two helices rotating in the same direction, that is both > ends will have the same direction of rotation. > > Can't help you with the rest unfortunately. > > > Cheers - Joe Hi Chris I have some thoughts to share about how the CP antennas need to be polarized, transmit and receive. But, I couldnt make any clearer than Joe does. Let me know if any additional text would be helpful. Jerry Article: 218829 of rec.radio.amateur.antenna From: nx7u@arrl.net (Scott Townley) Subject: Re: A few Helical Antenna question Message-ID: <436006b7.634430@news.west.cox.net> References: Date: Wed, 26 Oct 2005 22:49:00 GMT On Wed, 26 Oct 2005 12:07:11 -0500, Chris W <1qazse4@cox.net> wrote: >I am reading the 19th edition of the ARRL Antenna Book. I am unclear >which polarization to use if I want 2 Helical antennas to talk to each >other. In the book it says, ". . . when two stations use helical >antennas over a non reflective path, both must use antennas with the >same polarization sense.." I find this could be interpreted in >different ways and is not clear at all. It seems logical to me that if >both antennas had the same polarization that when they faced each other >they two helices would be in opposite directions and that would seem to >be bad. Am I right? Wind the two in the same "screw sense" (i.e., both clockwise out to the far end, or both CCW out to the far end) and they will be same sense. > >It says the circumference can be between 1.33 wavelengths and .75 >wavelengths. From the gain formula it would seem that the 1.33 figure >would give the most gain for a given length of the antenna. Other than >mechanical considerations is there any reason I wouldn't want to use the >1.33 number? The higher gains give higher sidelobes too. For earth-earth paths that probably isn't a major issue. For satellite work it can be significant. > >Finally, I may have missed it, but I didn't see anything that indicated >how large of a wire or tube I should use for the helix. I am guessing >this is just a mater of how much power I plan on feeding it with? Not really, any more so than with building a dipole. A popular material for 70cm is 1/4" copper tubing, which you can easily get in 50' lengths at the hardware store. Look for refrigerator tubing in the plumbing supply section. > >PS I would like to build 2 of these one is for 2.4ghz wireless network >and one is 432 mhz amateur band EME and or satellite work. So the >2.4ghz version will likely never see more than 100 mW but could see as >much as 1 watt. The 432 mhz version could see as much as 1000 watts, >but if I did that it would be to an array of 4 of them so I guess each >one would only see 250 watts? > True. But for EME/Satellite work, helices are not ideal for reception. Transmit is fine, but the sidelobe levels cause weak signal noise problems. If the satellite has plenty of downlink power it may not be a problem, but EME would definitely be an issue. Not to mention that you really need switchable polarization for EME, and to do that effectively with a helix requires two of them! >-- >Chris W > >Gift Giving Made Easy >Get the gifts you want & >give the gifts they want >One stop wish list for any gift, >from anywhere, for any occasion! >http://thewishzone.com Article: 218830 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <7l2ml1p4e9mjunf4ho30hd6uoj4e25756q@4ax.com> <6llql1p0a9j8jklleembj2hdhnlpuenma8@4ax.com> Date: Thu, 27 Oct 2005 06:37:17 GMT On Mon, 24 Oct 2005 18:03:49 -0400, TRABEM <> wrote: >>Assume the wire diameter is a conservative thick 2mm. >> > >Assume nothing Reg. Well T, reading through the thread you seem to be real short on relevant information (ie you don't adequately anticipate the information people need to answer your questions), then very ready to deal abruptly with people who make the wrong assumptions about the context. Owen -- Article: 218831 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: antenna lengths Message-ID: <5ju0m1977p4thid6gb09upudula83emqsh@4ax.com> References: Date: Thu, 27 Oct 2005 07:01:25 GMT On Wed, 26 Oct 2005 00:15:11 +0000 (UTC), "Reg Edwards" wrote: >> do you have theoretical or experimental support for the >> inference that insulated vs uninsulated wire will be different in >> length by around 3.5%? What thickness wire / insulation? >> >> Owen > >========================================= > >To calculate change in velocity due to plastic PVC insulation we need >to know :- > >Wire diameter = d >Diameter over insulation = D >Height of wire above ground = H >Permittivity of insulating material = K > >First calculate capacitance of bare wire to ground. >Then calculate capacitance of insulated wire to ground. >Velocity Factor = SquareRoot of their ratio. >Neither Terman's nor Kraus' Bibles will mention the following >formulae. So you'll just have to take my word for it. > > >Velocity Factor = SquareRoot( ( A + B ) / C ) > >Where - > >A = K * Ln( 4 * H / D ) > >B = Ln( D / d ) > >C = K * Ln( 4 * H / d ) > >Example : >Bare wire diameter = 1.6 mm = 14 awg. >Diameter over insulation = 2.6 mm. >Height above ground = 10 metres = 33 feet. >Permittivity of insulation = 3.5 > >Velocity factor = 0.983 >Or a decrease in resonant frequency of 1.7 percent which can nearly >always be forgotten about. > >The electrical effect of the enamel on magnet wire is entirely >negligible. But it does protect the wire from atmospheric pollution. Thanks Reg. I had not doubt there was an effect, but it was the arbitrary percentage figure that was implied irrespective of physical parameters which could have a large range (such as your examples). Clearly, the effect is a minor one in practical HF wire antenna cases compared to the influence of nearby structures, ground conditions etc, and one that is adequately dealt with by normal expectations of trimming length of an antenna for resonance (where that is the objective) rather than "designing" for the insulation factor. Owen -- Article: 218832 of rec.radio.amateur.antenna From: "Dale Parfitt" References: Subject: Re: A few Helical Antenna question Message-ID: Date: Thu, 27 Oct 2005 15:42:39 GMT > PS I would like to build 2 of these one is for 2.4ghz wireless network > and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz > version will likely never see more than 100 mW but could see as much as 1 > watt. The 432 mhz version could see as much as 1000 watts, but if I did > that it would be to an array of 4 of them so I guess each one would only > see 250 watts? > > -- > Chris W > EME on 432 is linearly polarized (although switching polarities to make up for Faraday rotation can be advantageous) - you'll be throwing away a huge 3dB, have higher sidelobes than a well designed Yagi (nullifying the low sky temp advantage of deep space) and less gain per boom length than a good Yagi- all in all, a dismal choice for EME. Dale W4OP Article: 218833 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: A few Helical Antenna question References: Message-ID: <707733-bio.ln1@p400bob.personal.cox.net> Date: Thu, 27 Oct 2005 10:06:13 -0500 Just an extra comment Chris. The "non reflective path" is also real important. As a circular polarised signal reflects off objects, it changes polarisation to the opposite sense. You'll find that "opposite polarised" in circular has far more (in practice) attenuation than for plane antenna cross polarisation. If your path has an odd number of reflections you have to use the opposite polarisation at each end. Cheers Bob VK2YQA Chris W wrote: > I am reading the 19th edition of the ARRL Antenna Book. I am unclear > which polarization to use if I want 2 Helical antennas to talk to each > other. In the book it says, ". . . when two stations use helical > antennas over a non reflective path, both must use antennas with the > same polarization sense.." Article: 218834 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: A few Helical Antenna question References: Message-ID: Date: Thu, 27 Oct 2005 12:53:11 -0500 Dale Parfitt wrote: > > PS I would like to build 2 of these one is for 2.4ghz wireless network > > >>and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz >>version will likely never see more than 100 mW but could see as much as 1 >>watt. The 432 mhz version could see as much as 1000 watts, but if I did >>that it would be to an array of 4 of them so I guess each one would only >>see 250 watts? >> >>-- >>Chris W >> >> >> > EME on 432 is linearly polarized (although switching polarities to make up >for Faraday rotation can be advantageous) - you'll be throwing away a huge >3dB, have higher sidelobes than a well designed Yagi (nullifying the low sky >temp advantage of deep space) and less gain per boom length than a good >Yagi- all in all, a dismal choice for EME. > >Dale W4OP > > > > The calculation in the ARRL Antenna book say that a 12 foot boom with a circumference of 1.33 wavelengths will give me a 19.9 dbi gain this should make up for the 3 db loss I think. I haven't seen a yagi that gives that much gain in with a 12 foot boom. The book also says that the side lobe problem can be significantly reduced by creating an array of 4 helical antennas. That should up the gain to 25.9 db. That's pretty good for EME isn't it? Take it to 16 and you get over 30 db gain. And the only need to be spaced at 1.5 wavelengths, that's only 3.4 feet. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218835 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: A few Helical Antenna question References: Message-ID: Date: Thu, 27 Oct 2005 13:01:04 -0500 Jerry Martes wrote: >"Joe McElvenney" wrote in message >news:u3hvl11t2tdbsch0eam6uqq1n4jhbc2dii@4ax.com... > > >>Hi, >> >> >> >>>other. In the book it says, ". . . when two stations use helical >>>antennas over a non reflective path, both must use antennas with the >>>same polarization sense.." I find this could be interpreted in >>>different ways and is not clear at all. It seems logical to me that if >>>both antennas had the same polarization that when they faced each other >>>they two helices would be in opposite directions and that would seem to >>>be bad. Am I right? >>> >>> >> On your first point, imagine you've constructed a long, long >>helix that starts at your location and travels all the way to the >>other station. It is logical that a wave launched by you would >>then travel unimpeded along it to the far location. Now cut the >>helix in the middle and turn one end around. What you will then >>see is two helices rotating in the same direction, that is both >>ends will have the same direction of rotation. >> >> Can't help you with the rest unfortunately. >> >> >> Cheers - Joe >> >> > > Hi Chris > > I have some thoughts to share about how the CP antennas need to be >polarized, transmit and receive. But, I couldnt make any clearer than Joe >does. > Let me know if any additional text would be helpful. > > Jerry > > > > No it makes perfect sense, I don't know what I was thinking. I mean if you take 2 right hand threaded bolts and have them face each other they are still right hand threaded and a nut will go of one and right on to the other spinning the same way. It's obvious now that I think about it. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218836 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1130172617.761487.141900@g14g2000cwa.googlegroups.com> <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Thu, 27 Oct 2005 14:55:32 -0400 Message-ID: <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> May I ask, what is with the almost fanitical adherence to Q? wrote in message news:3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com... > On 26 Oct 2005 09:27:44 -0700, "K7ITM" wrote: > > >I could perhaps scan the relevant pages of the references I > >mentioned... > > > > No, I can get them att he schools library I think. thanks for the > offer. > > >How are you planning to couple your 2-ohm load to your loop without > >doing really bad things to its Q? > > Is it better to convert the loop to a higher impedance just to feed it > into the house? It appears that anything I do is going to knock the > heck out of the antennas Q though. > > I have not decided whether to mount the receiver at the antenna yet, > or whether to run the twisted line directly into the house from the > antenna (since it's a short run). Most likely it will have a short run > of cat 5 cable going from the antenna to a 1 to 1 toroid transformer > located in the receiver. The only selectivity for the receiver will be > the antenna itself. The receiver is very small, and uses very little > power, so it's pretty feasible to mount the entire receiver at the > antenna and run a balanced line feed of the audio into the house. > > > (And just what sort of detector do > >you have that represents a 2 ohm load?) > > Is it better to convert the loop to a higher impedance just to feed it > into the house? > > It's an analog switch input, modified by my neighbor that gave me one > of them. The switch vendor says the switch series resistance should be > around 3 ohms, but it measures around 2.5 ohms. Probably is a little > lower than expected due to the integrating capacitors (.1 uF) which > are hung on the output of each switch. The .1's go to ground. > > I measured it twice, once with a 1:1:1 isolation transformer and once > with a 6:1:1 isolation transformer....The tester looses accuracy at > low impedances, so we repeated the measurement with the generator > feeding the high impedance side of the a transformer also. I got > nearly the same reading after correcting for the transformers > impedance step down value, since both readings agree pretty well with > the switch vendors ratings, it's very likely that the receiver input > impedance is around 2 ohms. > > > (And just what sort of detector do > >you have that represents a 2 ohm load?) > > > >Cheers, > >Tom > Article: 218837 of rec.radio.amateur.antenna From: Detlef Conradin Subject: Problem with nec2 Date: 27 Oct 2005 19:08:49 GMT Message-ID: <436125c1$0$1163$5402220f@news.sunrise.ch> Hi To get started with nec2 I tried to simulate a simple dipole. The graphical view of the pattern looks okay, however the gain seems to be to high. To what are the DBs refered in the output file? Or what do I have to change to get the gain in dBi ? Here is my input file: ----------------------------------------- CM Test CE GW 1 20 0 0.005 0 0 7.5 0 0.01 GW 2 20 0 -0.005 0 0 -7.5 0 0.01 GW 3 1 0 -0.005 0 0 0.005 0 0.01 GE 0 EX 0 3 1 1 10. 0 0 0 0 0 FR 0 30 0 0 6. 1. 0 0 0 0 RP 0 37 72 1001 0. 0. 5. 5. 1000 1. EN ----------------------------------------- Detlef PS: If I calculate the gain with the formula: 4 * Pi * r^2 * |E|^2 Gain = ----------------------- P_in * 2 * 120 * Pi by using the E-Field magnitude values from nec2's output I get also those very high values. (?) Article: 218838 of rec.radio.amateur.antenna From: "Dale Parfitt" References: Subject: Re: A few Helical Antenna question Message-ID: Date: Thu, 27 Oct 2005 19:15:57 GMT "Chris W" <1qazse4@cox.net> wrote in message news:ku88f.1019$ZP1.519@dukeread11... > Dale Parfitt wrote: > >> > PS I would like to build 2 of these one is for 2.4ghz wireless network >> >>>and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz >>>version will likely never see more than 100 mW but could see as much as 1 >>>watt. The 432 mhz version could see as much as 1000 watts, but if I did >>>that it would be to an array of 4 of them so I guess each one would only >>>see 250 watts? >>> >>>-- >>>Chris W >>> >>> >> EME on 432 is linearly polarized (although switching polarities to make >> up for Faraday rotation can be advantageous) - you'll be throwing away a >> huge 3dB, have higher sidelobes than a well designed Yagi (nullifying the >> low sky temp advantage of deep space) and less gain per boom length than >> a good Yagi- all in all, a dismal choice for EME. >> >>Dale W4OP >> >> > The calculation in the ARRL Antenna book say that a 12 foot boom with a > circumference of 1.33 wavelengths will give me a 19.9 dbi gain this should > make up for the 3 db loss I think. I haven't seen a yagi that gives that > much gain in with a 12 foot boom. The book also says that the side lobe > problem can be significantly reduced by creating an array of 4 helical > antennas. That should up the gain to 25.9 db. That's pretty good for EME > isn't it? Take it to 16 and you get over 30 db gain. And the only need > to be spaced at 1.5 wavelengths, that's only 3.4 feet. > > -- > Chris W The closest optimized Yagi I found was a K1FO on a 14' boom- 17.9dBi which compares quite well with your 19.9dBi on a 12' boom once we adjust for the polarization loss making the helical 16.9dBi linear for the helix vs. 17.9dB for the K1FO My experience with EME is at 23cM where we use dishes- but I can tell you that 1dB is to kill for.. The circularity could be an advantage as it would be insensitive to Faraday. Another advantage is that they are non critical to build- at least from a gain standpoint. But I think the real issue will be weight and weight ditribution. Between the helical tubing, non conductive boom and the reflector screen a helix is going to be a clydesdale compared to a Yagi. Another problem might be the necessity to mount the array from behind the reflector- that's going to be quite a moment arm. Bottom line is, 432 MHz EME is well explored- I am not aware of the use of helices for EME there- although, again I am not active on 432 EME. If they are not being use, there's probably a reason. Dale W4OP Article: 218839 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: A few Helical Antenna question Date: Thu, 27 Oct 2005 14:16:15 -0500 Message-ID: <2204-4361277F-73@storefull-3257.bay.webtv.net> References: Chris W. wrote: "I am unclear which polarization to use if I want 2 helical antennas to talk to each other." Unless you are bouncing the signals off a reflector, use the same polarization for both. The axial-mode helical antenna is circulaly polarized and fires along its axis away from its ground screen. It can be either left handed or right handed depending on which way the helix twists. It responds to vertical, horizontal or diagonally polarized waves. It does not respond to waves with the opposite twist to its helix. Circular polarization of the opposite twist is rejected. This is like machine bolt threads. A bolt can screw into a nut from either side if it has the same itch direction, but a left hand bolt won`t screw into a right hand nut. Circular polarization of the opposite rotation is rejected. Refer to any edition of "Antennas" by Kraus for the details. Kraus invented the helical antenna after other experts said it could not work. Best regards, Richard Harrison, KB5WZI Article: 218840 of rec.radio.amateur.antenna From: "K" References: <1130172617.761487.141900@g14g2000cwa.googlegroups.com> <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: Date: Thu, 27 Oct 2005 19:42:05 GMT Hooey Boy, are you gonna get an earfull now! How dare you ask something like that! You just evoked the wrath of flag, momma, and God! har.. J "Fred W4JLE" wrote in message news:764dd$436122fa$97d56aa2$21648@ALLTEL.NET... > May I ask, what is with the almost fanitical adherence to Q? > > wrote in message > news:3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com... >> On 26 Oct 2005 09:27:44 -0700, "K7ITM" wrote: >> >> >I could perhaps scan the relevant pages of the references I >> >mentioned... >> > >> >> No, I can get them att he schools library I think. thanks for the >> offer. >> >> >How are you planning to couple your 2-ohm load to your loop without >> >doing really bad things to its Q? >> >> Is it better to convert the loop to a higher impedance just to feed it >> into the house? It appears that anything I do is going to knock the >> heck out of the antennas Q though. >> >> I have not decided whether to mount the receiver at the antenna yet, >> or whether to run the twisted line directly into the house from the >> antenna (since it's a short run). Most likely it will have a short run >> of cat 5 cable going from the antenna to a 1 to 1 toroid transformer >> located in the receiver. The only selectivity for the receiver will be >> the antenna itself. The receiver is very small, and uses very little >> power, so it's pretty feasible to mount the entire receiver at the >> antenna and run a balanced line feed of the audio into the house. >> >> > (And just what sort of detector do >> >you have that represents a 2 ohm load?) >> >> Is it better to convert the loop to a higher impedance just to feed it >> into the house? >> >> It's an analog switch input, modified by my neighbor that gave me one >> of them. The switch vendor says the switch series resistance should be >> around 3 ohms, but it measures around 2.5 ohms. Probably is a little >> lower than expected due to the integrating capacitors (.1 uF) which >> are hung on the output of each switch. The .1's go to ground. >> >> I measured it twice, once with a 1:1:1 isolation transformer and once >> with a 6:1:1 isolation transformer....The tester looses accuracy at >> low impedances, so we repeated the measurement with the generator >> feeding the high impedance side of the a transformer also. I got >> nearly the same reading after correcting for the transformers >> impedance step down value, since both readings agree pretty well with >> the switch vendors ratings, it's very likely that the receiver input >> impedance is around 2 ohms. >> >> > (And just what sort of detector do >> >you have that represents a 2 ohm load?) >> > >> >Cheers, >> >Tom >> > > Article: 218841 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <39m0m1dr0l63m0p867vu4h532sbnhshe19@4ax.com> <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: Date: Thu, 27 Oct 2005 20:12:30 GMT Hi Trabem I've been trying to follow this thread because I like to play with tuned loop antennas for broadcast band reception. I missed the part about how much this 20 meters of #2 copper cable with its support weighs. Your project sounds Serious. That antenna must weigh close to 500 pounds The loop antennas I've been building are large diameter coils of smaller wire. I recognize that the type antenna I build arent acceptable for your consideration. But, I do have some experience with using a low freq loop in the city. If you are located near man made noise, it is very likely that resonating the loop doesnt result in highest Signal/Noise ratio. Perhaps you already have experience with Low Freq loops and can tell me about your experiences. I am interested in learning. Jerry wrote in message news:b5o1m1tnf9ouuhb0o5gqb0b8c9fh0c1gm0@4ax.com... > >> >>>You should have the schematic in your mailbox by the time you get this >>>message. >> >>If I am to translate the annotation correctly (and it is obviously in >>error - R10 and R12 are not the pair being changed), then Input Z >>somewhere in your frequencies of interest (you've named several) runs >>around 10 Ohms with the switch itself attenuating your signal by 6 to >>10dB. This, of course, says nothing of the abysmal match to the >>antenna whose Q will be buried in potter's field. > > Hi Richard, > > You are correct, the resistors being changed at R11 and R12, sorry for > the error. To correct the statement on the schematic, consider R11 and > R12 as being changed from 10 ohms to .2 ohms. > > I'm not sure what the 'abysmal match to the antenna whose Q will be > buried in potter's field' statement is about. With my antenna being in > the 2 ohm impedance range, and the receiver being at 10 ohms (I'll use > your figure), how can the match be abysmal? Granted, it's not anywhere > near ideal. Have you assumed I was using a parallel tuned loop? > > Since power transfer is the goal, and the antenna has a lot of ability > to reject out of band signals, it was my hope to use the antenna > itself as the only (purposely) tuned circuit in the system. Wouldn't > converting the antenna impedance to a more traditional 50 ohms with a > toroid, and then having a second toroid to convert it back down to 10 > ohms also be destructive to the antenna Q and lossy? > >> >>I gather that the switch operates as a baseband quadrature/synchronous >>detector. It looks suspiciously like it will either short the input, >>or leave one half dangling, but I trust you got the schematic from a >>good source. I won't bother to try to verify the logic. >> > > The logic is good, trust me, the receiver as shown outperforms many > much more expensive ones on the market currently. It is based on the > receiver shown at: > > http://www.qrp2001.freeserve.co.uk/qrp2001rf.gif > > It's design has been around for awhile, the first prototype was built > in 2000. While I disagree with the use of resistive matching, it > should be ok at VLF as the signals are usually quite large there to > begin with. For a simple receiver, it is the best answer. Although > ideally, each switch should have it's own 1 ohm variable resistor for > absolute best results...the purpose being to swamp out the dynamic > switch series resistance differences. > > Note the receiver has no rf amp, it isn't needed. The gain is provided > by some low noise op amps, and no rf stage is needed. The QRP2001 > receiver is designed for 100 KHz to 30 Mhz, but it is only rated down > to 1.8 MHz. However, it's worst case sensitivity is .4uV for 10 db > sinad. > > >>The roll-off frequency of the amplifier(s) is at the bottom of the AM >>band, it would do better to track the oscillator frequency about one >>seventh below so that AM signals are depressed below WWVB instead of >>competing with it. Increase the caps from 470pF to 3300pF. >> > > Agreed. Thanks. > > The 470 pF value was chosen for a wide band spectral display from DC > to 96 KHz, which is about the best that generic PC sound cards can do > today. If the panoramic view of the surrounding spectrum wasn't > necessary, these caps would be much larger in value. As it sits > however, it's nice to have a panoramic view of the surrounding > spectrum, so the caps might not be changed. > > For my purposes, they don't need to be nearly as small as they are, > but the original design was for HF...where a wiew of the surrounding > spectrum was handy. > >>The reason why you want low front end Input Z is to satisfy the >>amplifier topology (the gain will be roughly half what it is probably >>specified at). This could have been done better in half a dozen >>different ways with the same active parts. >> >>The problem here is some bozo marked the input "antenna" and removed >>the necessary follower amplifier that would have been fed by the >>antenna which would in turn feed this circuit through the transformer. >>This sucker, as drawn, is going to be deaf, deaf, DEAF. If you hear >>WWVB it will be by virtue of their strong power, not by any quality of >>design here. >> > > WRONG, but I think I understand your error. BTW, the 'bozo' was me:>:. > > Again, I think you've assumed it would be fed with a parallel loop > resonant antenna. > > And, no active components are needed for outstanding performance. > > It is possible that the antenna circuit might need to be tuned with > passive components, but that possibility needs further evaluation. > >>To unplug this design's ears and make up for the massive goof, add a >>FET follower. Load the FET drain with a 2.2 Ohm resistor and make >>sure you couple the signal through a large cap feeding the >>transformer. Also, bias the FET on with a hi Z divider so you don't >>wipe out the Q of the antenna. I will bet that even the proposed "I" >>and "Q" paths are mislabled or missapplied. >> > > OK, this is a fair request...from someone without experience in this > type of receiver. However, in reality, an rf stage of any sort is > unnecessary. > > Again, I think you're trying to match a 2 K parallel tuned loop to the > relatively low impedance of the receiver input. I noticed you said > 'follower'. Which, I think means unity gain, but is used for impedance > matching. > > Any active component before the audio op amp is STRONGLY > DISCOURAGED in this type of receiver. This includes back to back > diodes as the receiver switches can handle 4v p-p. It also includes > varicap tuning diodes. A front end rf amp should be avoided at all > costs, it can only degrade the performance of this type of receiver. > > The receiver has incredible immunity to strong out of band signals, > much more than any superhet. The nature of the beast is that the > quadrature detector cancels them out by (effectively) NOT reinforcing > them. The desired signal is however very strongly reinforced. Since we > don't need an rf amp to get good sensitivity, any active component > before the load capacitors is strongly discouraged. > > Even at 60 MHz, the performance is only slightly degraded, and that is > due to the inability of the analog switch to enable and disable fast > enough to allow reception there. There is a commercial application > using this technology that implements receive and transmit with analog > switch method and it does not have an RF amp. > > Of course, there is a trade off. In order to obtain immunity from > strong adjacent out of band signals, we give up the ability to reject > harmonics. Harmonics are only attenuated 6 db....so a tuned input must > be used if the antenna cannot adequately prevent harmonics of the > receiver frequency from entering the receiver. > > In theory, a minimum of 6db enhancement is available because there is > no mixer, so there is no conversion loss! > > The susceptibility to harmonics is a small trade off. Remember, a > receiver of this type is wideband, needs no conventional mixers, no > detector diode, no transformers, no crystal filters, no IF amps, has > no conversion loss and no major non-linear components...thus offers > outstanding performance with the cost to build very much reduced > (relative to a superhet). What you don't see on the schematic is the > incredible sound of the receiver audio which is clean and crisp...it's > not quantifiable by bench measurements however. > > I've put some links to web references of this technology at the end of > the message. > > In the meantime, I'd appreciate comments regarding the issue of how > well the loop will feed the antenna input for the modified receiver > schematic I sent you by email. > > Regards, > > T > > PS:I hope Dave is still with us. Although he probably left when he > assumed I measured the input impedance with an ohm meter:>: Dave, are > you able to concede that the input impedance of the receiver might be > around 2 (or 10) ohms now? > > > ----------------------------------------------------------- > > If you want read up on this type of receiver, I can recommend the > following: > > > http://www.qrp2001.freeserve.co.uk/contact.htm > > http://www.flex-radio.com/ > > Flex-Radio makes the quadrature based SDR-1000 transceiver. For a very > detailed explanation (without heavy math) of the detector theory, > check out the QEX article, part 1 at: > > http://www.flex-radio.com/articles_files/SDRFMP1.pdf > > And, there are independent product reviews for the SDR-1000 at: > > http://www.flex-radio.com/articles_files/index.htm > > Dan Tayloes NC2030 high performance signle band transceiver is > detailed at: > > http://www.qslnet.de/member/df7tv/nc2030_pres_2004_10.pdf > > The complete schematics for the NC2030 are at: > > http://www.norcalqrp.org/nc2030.htm > > Note that the NC2030 uses the same type of detector, but does not use > a sound card and does not rely on a computer at all. It is a stand > alone transceiver. > > There is also a 9Y4 who home brewed a complete transceiver, details > at: > > http://9y4ar.tripod.com/tayloe_mixer.htm > > Although slightly off topic, a low power ssb/cw exciter can be made > just as easily as the receiver using the same analog switch > technology. The process is simply the reverse process of the detector. > To see how simple a high quality transmitter is, try: > > http://www.w1tag.com/Phasing.htm > > > . > Article: 218842 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Thu, 27 Oct 2005 13:25:49 -0700 Message-ID: References: <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <39m0m1dr0l63m0p867vu4h532sbnhshe19@4ax.com> <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> Richard Clark wrote: > This is comparing apples and donuts when the menu only offers steak. What kinds of steak are on the menu? I haven't had lunch yet and I could go for a nice Chateaubriand. By the way, some kinds of donuts have apples in them. Apple fritters I think they call them. In a way they're both apple AND donut - since you brought it up. ac6xg Article: 218843 of rec.radio.amateur.antenna From: "Frank's" References: <436125c1$0$1163$5402220f@news.sunrise.ch> Subject: Re: Problem with nec2 Message-ID: Date: Thu, 27 Oct 2005 21:51:42 GMT "Detlef Conradin" wrote in message news:436125c1$0$1163$5402220f@news.sunrise.ch... > Hi > > To get started with nec2 I tried to simulate a simple dipole. > The graphical view of the pattern looks okay, however the gain seems > to be to high. To what are the DBs refered in the output file? > Or what do I have to change to get the gain in dBi ? > > Here is my input file: > ----------------------------------------- > CM Test > CE > GW 1 20 0 0.005 0 0 7.5 0 0.01 > GW 2 20 0 -0.005 0 0 -7.5 0 0.01 > GW 3 1 0 -0.005 0 0 0.005 0 0.01 > GE 0 > EX 0 3 1 1 10. 0 0 0 0 0 > FR 0 30 0 0 6. 1. 0 0 0 0 > RP 0 37 72 1001 0. 0. 5. 5. 1000 1. > EN > ----------------------------------------- > > Detlef > > PS: > If I calculate the gain with the formula: > > 4 * Pi * r^2 * |E|^2 > Gain = ----------------------- > P_in * 2 * 120 * Pi > > by using the E-Field magnitude values from nec2's output I get also > those very high values. (?) > Hi, you have a segment length violation in TAG 3; it is very short, being only 5mm. Also short when compared to the segment length in TAGs 1 and 2 at 37.5 cm. It is a good idea to maintain equal segment lengths in the entire model, with minimum lengths not exceeding 0.001 wavelengths on any frequency. I have modified your code as shown below. There is nothing wrong with breaking the wire up into three tags, but they should all run the same way. Your end TAGs are running in opposite directions, which will cause current discontinuities in plots, and NEC output file data. There was something weird about your RP card also, but have not yet delved into what is wrong. I have not checked, but your computation of gain with the E-field should now be correct. Cebik's book on NEC modelling, at www.nittany-scientific.com, for $50 is well worth the money. Regards, Frank CM Test CE GW 1 21 0 -7.5 0 0 7.5 0 0.01 GS 0 0 1.000000 GE 0 GN -1 EX 0 1 11 00 10. 0 0 0 FR 0 30 0 0 6. 1. 0 0 0 0 RP 0 181 1 0000 -90 0 1.00000 1.00000 1000 1. EN Article: 218844 of rec.radio.amateur.antenna From: "Frank's" References: <436125c1$0$1163$5402220f@news.sunrise.ch> Subject: Re: Problem with nec2 Message-ID: Date: Thu, 27 Oct 2005 22:43:55 GMT "Detlef Conradin" wrote in message news:436125c1$0$1163$5402220f@news.sunrise.ch... > Hi > > To get started with nec2 I tried to simulate a simple dipole. > The graphical view of the pattern looks okay, however the gain seems > to be to high. To what are the DBs refered in the output file? > Or what do I have to change to get the gain in dBi ? > > Here is my input file: > ----------------------------------------- > CM Test > CE > GW 1 20 0 0.005 0 0 7.5 0 0.01 > GW 2 20 0 -0.005 0 0 -7.5 0 0.01 > GW 3 1 0 -0.005 0 0 0.005 0 0.01 > GE 0 > EX 0 3 1 1 10. 0 0 0 0 0 > FR 0 30 0 0 6. 1. 0 0 0 0 > RP 0 37 72 1001 0. 0. 5. 5. 1000 1. > EN > ----------------------------------------- > > Detlef > > PS: > If I calculate the gain with the formula: > > 4 * Pi * r^2 * |E|^2 > Gain = ----------------------- > P_in * 2 * 120 * Pi > > by using the E-Field magnitude values from nec2's output I get also > those very high values. (?) > PS, also confused by your formula. Which Value of E are you using? Are you trying to calculate the "Total radiated power" (TRP)? If so you need to integrate the power density over a spherical region. The calculation is greatly simplified if you take advantage of any natural symetry in the radiation pattern -- i.e. integrate from axis end to axis end, then multiply by 2*PI -- as in elementary calculus, you are using a single integral for a "Solids of revolution" method, instead of a double (Surface integral). If you are trying to caluculate the gain in a given direction you need to take 20*log(E/Ei). Where E is the NEC calculated E field in the desired direction, and Ei is the computed E field from an ideal isotropic source with the same input power as the test antenna. As for your RP card, I notice that you are attempting to vary both "Theta" and "Phi". I usually keep one fixed and vary the other, but to be honest I am not sure if what you are doing is incorrect, although I notice that the "Phi" pattern is only computed for one frequency. The only other difference is that I normally do not use gain averaging. Also using 1 degree increments does not seem to slow things down very much. With your RP card I was also getting some weird pattern discontinuities. Regards, Frank Article: 218845 of rec.radio.amateur.antenna From: "Frank's" References: <436125c1$0$1163$5402220f@news.sunrise.ch> Subject: Re: Problem with nec2 Message-ID: Date: Thu, 27 Oct 2005 22:48:41 GMT ........entire model, with minimum lengths not exceeding 0.001 wavelengths on any > frequency. I have .... Oops, of course, I meant: "Not less than 0.001 wavelengths". Frank Article: 218846 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <39m0m1dr0l63m0p867vu4h532sbnhshe19@4ax.com> <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> Date: Fri, 28 Oct 2005 01:48:54 GMT On Thu, 27 Oct 2005 20:52:45 -0400, TRABEM <> wrote: >That being said.... ... >I have a series resonant loop with moderately large conductor wire and >reasonably high Q capacitors. It's tuned to resonate at 60 KHz. Is that to mean the loop circuit consists of an inductor (including its radiation resistance and copper losses) of about j10 ohms and a capacitor (including its losses) of about -j10 ohms and a load resistance (being the 2 to 10 ohms receiver input Z) in series (ignoring transmission line for the moment)? You quote a Q figure and talk about expected bandwidth earlier in the thread. Wary of making any unwarranted assumptions, is it safe to assume that you know that it is the loaded Q that will determine the bandwidth of the circuit in operation? If you insert the rx input Z in series in the loop as described above, you don't need a calculator to see that the loaded Q cannot be 200+, and you might be lucky if it is better than 5 if the numbers you have quoted are correct. This circuit is not likely to give you much front end selectivity, is it? Perhaps you need to consult a textbook to review your understanding of unloaded Q, loaded Q, efficiency, and bandwidth, and where to apply which Q value. Owen -- Article: 218847 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <39m0m1dr0l63m0p867vu4h532sbnhshe19@4ax.com> <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> Date: Fri, 28 Oct 2005 03:00:00 GMT On Thu, 27 Oct 2005 22:38:47 -0400, TRABEM <> wrote: >Hi Owen, > >Hi Owen, > >I am using large copper cable and relatively low loss capacitors. I >expect the 9 ohms of inductive reactance to cancel out the -9 ohms of >capacitive reactance leaving only the sum of the AC (or RF) resistance >of the copper and the ac resistance of caps to give me my net >impedance. Am I correct up to this point?? > >I'm trying to take this step by step so I can understand where I've >gone wrong.....clearly I must have made an error somewhere. > >I don't know what the actual ac resistance of the caps is, but I do >know the ac resistance of 20 meters of #2/0 copper welding cable is >pretty damn low. > >Yes, the loop is series tuned, so the output is taken on the >unconnected capacitor terminal and the unconnected wire end. > >Rjeloop3 gives estimates my Q at 221 even though it thinks I'm >building a parallel tuned loop. But, I think Q is Q, and the Q of both >types of loops is the same provided the same materials have been used >in both loops. > Forget Rjeloop3 for the moment and think about what you have. You focus on how low the resistance of the loop inductance is, and whether or not the capacitor ESR is significant... neither is when you jam a 2 ohms receiver in series with it all (ignoring the transmission line). You seem to be analysing your series circuit with part of it (the rx) replaced with a s/c. >I am (for now) not considering the effects of hooking it to a receiver >and/or the transmission line. I confess I have not tried to quantify Well, what good is it to know what the loop L and C do when not connected to the receiver? >the actual values of the ac resistance of the copper and have only >rough estimates of what the esr of the caps is. I'd be pretty >surprised if the dc resistance of the cable is much more than .1 ohms >though, so the ac resistance should be a little higher at 60 KHz. > >Can you estimate what the unloaded Q of the loop is (in round >numbers), and if so, can you agree that it might be around 221 (as >Reg's software predicts)? Can you estimate what the impedance of the >loop is (in round numbers)? Again, do not factor in the receiver input >impedance as we aren't sure whether I'll keep it as is or match it's >impedance with a preamp and/or toroidal transformer. For the moment, >assume the receiver is mounted at the loop (which is a very real >possibility since it's fairly small). Read Richard's response, though it is more detailed and no doubt more accuracy. I think you will understand the problem when you analyse a three component series circuit (your topology), the Loop L, the Loop C and the Rx input z. (You can ignore radiation resistance, loop loss, capacitor loss, they are all much less than rx input z so the loops loss is dominated by the rx input z in your circuit.) The place this will end up is that you will come to realise that knowing how the L and C of the loop behave unloaded, and dwelling on that behaviour ignoring the effect of loading is probably why you are where you are (an assumption I know). When you have worked that out, you may understand why others are asking how you are going to couple to the loop. Your proposal to insert the 2 ohms (or whatever) rx input in series with the loop components isn't delivering what you wanted, and it won't matter how thick the loop conductor is, or how low the ESR of the capacitor is. Owen -- Article: 218848 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 00:09:57 -0400 Message-ID: In a series resonant circuit, at resonance it is equivalent to a dead short (disregarding the R of the circuit). Series resonant circuits are usually used as traps. To develop a voltage one needs a parallel resonant circuit at the resonant frequency, The Q will simply determine how quickly the voltage falls off each side of resonance. Next there are two types of Q, first the calculated unloaded Q and second the in circuit or loaded Q. I think you are heading down the wrong path with the series circuit as your fighting a loosing battle. Assuming a perfect coil and capacitor you create an infinite Q circuit. Now you hook it up in your circuit. First there has to be enough resistance to develop the voltage , and here is the rub, as you increase the resistance to develop a voltage you decrease the Q. Yuk! Go with a parallel circuit like the rest of the world uses and you will be going in the right direction. wrote in message news:d113m196ib2c4khminc246f8hr0jkitrg6@4ax.com... > On Thu, 27 Oct 2005 14:55:32 -0400, "Fred W4JLE" > wrote: > > >May I ask, what is with the almost fanitical adherence to Q? > > Sure, it's a fair question. > > I have a simple receiver with a low impedance input that is few with a > toroid transformer and a tuned circuit to match the impedances and to > keep out of band signals out. > > I want to convert the receiver from HF to VLF (60 KHz) and to use a > series tuned loop of high Q as an antenna. In order to simplify the > receiver input, I have mentioned as an option to eliminate the 50 ohm > matching transformer and the tuned circuit in the front end of the > receiver....and to feed it directly with my low impedance loop. In > this way, the loops high Q would serve as the only means of preventing > out of band signals from getting into the receiver. > > In order to make sure that actually happens, I suggested making the > loop Q as high as possible. > > Hence my 'almost fanatical adherence to Q' > > Not sure if it will work, but wanted to run it past the group. > > Regards, > > T > > > Article: 218849 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <39m0m1dr0l63m0p867vu4h532sbnhshe19@4ax.com> <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> Date: Fri, 28 Oct 2005 04:50:15 GMT On Fri, 28 Oct 2005 03:00:00 GMT, Owen Duffy wrote: >I think you will understand the problem when you analyse a three >component series circuit (your topology), the Loop L, the Loop C and >the Rx input z. (You can ignore radiation resistance, loop loss, >capacitor loss, they are all much less than rx input z so the loops >loss is dominated by the rx input z in your circuit.) So... if you did this, and you want the loop to give you front end selectivity, and you want the bandwidth to be xxx which led you to want the LOADED Q to be 100 or more (whatever), you now know that the load introduced by the receiver into the series loop you have dictated needs to be better than (<) XL/Qloaded or < 0.1 ohms (not twenty or more times that value). How can you deliver a load impedance to the loop derived from the rx input circuit and its transmission line that is efficient and less than 100 milliohms (at the loop)? Is your single turn series loop idea practical at 60KHz? Owen -- Article: 218851 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 08:23:38 +0000 (UTC) Message-ID: References: <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> <7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com> wrote in message news:7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com... > > > > >I think you are heading down the wrong path with the series circuit as your > >fighting a loosing battle. Assuming a perfect coil and capacitor you create > >an infinite Q circuit. Now you hook it up in your circuit. First there has > >to be enough resistance to develop the voltage , and here is the rub, as you > >increase the resistance to develop a voltage you decrease the Q. Yuk! > > > >Go with a parallel circuit like the rest of the world uses and you will be > >going in the right direction. > > > I think I'm starting to get it. Am I cutting off my foot to spite my > face::> > > Comments made by you and a few others have nudged mein the right > direction..... > > The higher I make the series resonant Q, the lower the impedance goes, > hence it's almost impossible to get a lot of voltage out of it?? > > Not sure why it matters that much. But, I was under the impression > that a perfectly matched antenna and front end would only decrease the > Q by a factor of 2. > > Follow along with Richard's comments if you like and add your comments > as I check here often and read everything, sometimes many mant y > times:>: > > Regards, > > T > > PS:I had begun thinking that the higher imedance presented by a > parallel loop was harder to match with a balun, which is why I started > thinking of a series loop. I'm gettin there, thansk again. > ======================================= Trabem, This discussion is getting you nowhere very fast. So let's summarise. I don't have your exact dimensions but the following are good enough. L = 27uH, Reactance = j10 ohms, Conductor loss = 0.05 ohms, ESR = 0.01 ohms, Radiation ohms = 0. Receiver input = 10 ohms, Ground loss ohms = 0.01 The intrinsic Q of the loop is 10 / 0.05 = 200. The working Q of the loop, when series connected, is Reactance divided by the SUM of all resistances including the receiver. Working Q = Reactance / ( 0.05 + 0.01 + 10 + .01 ) = 10 / 10.07 = 0.993 Take note of the ridiculous low value of working Q due to the loop being in series with the receiver. ---- Reg. Article: 218852 of rec.radio.amateur.antenna From: Detlef Conradin Subject: Re: Problem with nec2 References: <436125c1$0$1163$5402220f@news.sunrise.ch> Date: 28 Oct 2005 09:20:55 GMT Message-ID: <4361ed77$0$1153$5402220f@news.sunrise.ch> >> To get started with nec2 I tried to simulate a simple dipole. >> The graphical view of the pattern looks okay, however the gain seems >> to be to high. To what are the DBs refered in the output file? >> [...] >> If I calculate the gain with the formula: >> >> 4 * Pi * r^2 * |E|^2 >> Gain = ----------------------- >> P_in * 2 * 120 * Pi >> >> by using the E-Field magnitude values from nec2's output I get also >> those very high values. (?) > PS, also confused by your formula. Which Value of E are you using? Are you The formula should be correct: I just use the magnitude value of the E Field. The intensitiy W_rad is then 0.5 * |E|^2 / Z_w (E and H are in phase and orthogonal in the far field) The radiation density U is then r^2 * W_rad (Unit: Watt per solid angle) The radiation density U_0 of an isotropic radiator with a total radiated power P_rad is: P_rad / (4 * Pi). The gain is then U/U_0 (or in dBi: 10*log(U/U_0) ). > trying to calculate the "Total radiated power" (TRP)? If so you need to > integrate the power density over a spherical region. The calculation is Yes, but nec2 shows the total radiated power in its output. > As for your RP card, I notice that you are attempting to vary both "Theta" > and "Phi". I usually keep one fixed and vary the other, but to be honest I > am not sure if what you are doing is incorrect, although I notice that the > "Phi" pattern is only computed for one frequency. The only other difference No thats no true. In the output file I can see E_phi as well as E_theta for every combination of phi and theta (for every frequency). I use the programm Xnecview to view the pattern and it has problems if you don't have points over the full sphere. > is that I normally do not use gain averaging. Also using 1 degree The average gain (over the full sphere) should probably be 1 (or 0 dBi). I get 0.991. Thanks for you help! The bad computation was caused by the stupid segementation I had chosen. Detlef Article: 218853 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 15:27:39 +0000 (UTC) Message-ID: References: <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> <7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com> Dear Trabem, The input impedance seen looking into the series-connected loop is the RF loss resistance of the loop, in your case about .05 ohms. If 0.05 is impedance-matched to a 10-ohm receiver then the working Q only falls to about 100. But it is not an easy matter to match 0.05 ohms to 10 ohms at 60 KHz. ( I do not know the precise input resistance of your receiver but you get the idea.) The working Q of any tuned circuit, either series or parallel connected, when impedance-matched to a load, always results in the working Q becoming equal to half of the tuned circuit's intrinsic Q. This is rather obvious because the loss resistance of the tuned circuit and the load (after being transformed to the tuned circuit value) are equal to each other. Of course, impedance-matching also results in maximum voltage and maximum current being developed in a given load (or receiver). Which is also a desirable condition. It is a serious mistake to think in terms only of volts-input to the receiver. Or only current-input to the receiver. Receiver S-meters are POWER meters. That's why they can be calibrated in decibels or in terms of 6dB per S-unit. Or S9 plus so many decibels. For example, with a 50-ohm receiver, the reference level S9 = 50 pico-watts receiver input power. Please accept my apologies for digressiing from 5-metre square loops at 60 KHz. ---- Reg. Article: 218854 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 16:24:39 +0000 (UTC) Message-ID: References: <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> <7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com> The mixed-up confusion along this extended thread is due to the inability of contributors to describe in plain English exactly what they mean about a relatively simple matter. It's a breeding ground for baffle-gab, confusing nonsense and old wives. To avoid wasting more time I respectfully suggest Trabem obtains a big bunch of capacitors of various values and gets on with the job. We will all be very interested in the outcome. Now perhaps we can return to which part of a 1/2-wave dipole does the most radiating - the middle bit or the ends? ---- Reg, G4FGQ. Article: 218855 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 16:46:15 +0000 (UTC) Message-ID: References: <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> <7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com> By the way, I consider the most sensible and understandable contributions to this thread have been the questions asked by the originator, Trabem. I am now half-way down a bottle of South African red plonk. It's supposed to be good for the arteries. ---- Reg, Hic. Article: 218856 of rec.radio.amateur.antenna From: "Asimov" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: Date: Fri, 28 Oct 2005 17:37:32 GMT "TRABEM" bravely wrote to "All" (28 Oct 05 00:42:15) --- on the heady topic of "Re: HIGH Q CAPS FOR VLF LOOP ANTENNA?" TR> From: TRABEM <> TR> Xref: core-easynews rec.radio.amateur.antenna:219360 This should require a matching transformer otherwise not enough current can flow to take advantage of the potentially huge Q. Without current flow there will be no energy storage in a series circuit. In a parallel circuit the current flow is internal between the parallel reactances but in a series circuit it must be external. A series circuit is naturally current driven so the transformer would basically be converting current into a voltage that the receiver input can use. If you measure your loop with a test signal you should find it requires a lot of current and little voltage. From your investigations, calculate the effective resistance and use this as your Rs to find the actual Q and the matching turns ratio required for an autotransformer, for example. Good luck, A*s*i*m*o*v ... Why is Brassiere singular and Panties plural??? Article: 218857 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 19:23:28 +0000 (UTC) Message-ID: References: <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <997vl1ldsfroag1bsdgfomq0jg5cp0nnbn@4ax.com> <1130344064.817342.63120@f14g2000cwb.googlegroups.com> <3bm0m1dmvfl7l94m5vqnhtm3pae9kuls0p@4ax.com> <764dd$436122fa$97d56aa2$21648@ALLTEL.NET> <7o93m1p82gc2fks232ojbb2f87u3v4odpc@4ax.com> Trabem, Without wishing to detract you in any way from your objective of a matched series tuned loop I would like to describe how I would do a similar job with the usual parallel tuned, multiturn loop. I do not understand the type of receiver you propose and I am not seriously interested. But I should say the theoretical working bandwidth of my proposal is about 1/2 of yours. Actual bandwidth of both your and my proposals is indeterminate because of the uncertainty of ground proximity and nearby environmental loss. The working bandwidths could be very similar. Using similar size loop dimensions to yours, ie., 5.3 metres square - Frequency = 60 Khz. 5 turns of close wound 2mm diameter enamelled wire. Inductance = 710 micro-henrys. Tuning capacitor = 0.01 uF approx. Reactance of L and C = 268 ohms. Conductor resistance loss = 2.5 ohms. Intrinsic coil Q = 107 Matched working Q =53 3dB working bandwidth = 1.12 KHz. Impedance match to 50-ohm receiver obtained via small coupling loop, in the same plane, about 1 metre square. Working Q = 53 or less depending on height above ground. The working Q may not be high enough for your particular application. I describe the antenna for you to see what is possible in comparison with your series-tuned proposals. ---- Reg, G4FGQ. Article: 218858 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: <9115m15iqhe74025ikjp6s1titp638oe7u@4ax.com> References: <95r0m15arpc63lg4rduhho9mmtbmuth2u9@4ax.com> <8pt0m1502qj8kv8lqnirsqtndn89t6bnkg@4ax.com> <4ge3m113gs5l2bk9pfr7jalmk32r01ce94@4ax.com> <54h4m1hmsc2cl64evcupb4uoa74lf6v07c@4ax.com> Date: Fri, 28 Oct 2005 20:12:48 GMT On Fri, 28 Oct 2005 09:02:14 -0700, Richard Clark wrote: >That is the point of my questions. They are veiled implications, not >tests of knowledge. No one in your list of links, much less those >I've read over the years knows the PRACTICAL implication of the "I" >and "Q" channels. So, I may as well drop the other shoe. > Didn't Don Stoner describe a synchronous detector way back. I think I remember reading an article in the mid sixties in "The Sideband Handbook" or similar. I was about 15 then, so a detector that had something like 17 bottles in it seemed overkill when I was copying CW and SSB on an AM receiver (ie diode detector) with BFO. The appeal being an all-mode detector (including DSBSC), but synchrounous detectors didn't seem to catch on in comms receivers, well not until DSP detection... well I don't recall coming across them anyway. Owen -- Article: 218859 of rec.radio.amateur.antenna From: Ron Subject: Antenna gain question Message-ID: Date: Fri, 28 Oct 2005 20:37:07 GMT Assume an incoming rf signal has exactly the same strength in all 3 dimensions i.e., completely omnidirectional. Question: would an antenna having gain capture any more signal power than a completely omnidirectional antenna with no gain? Ron, W4TQT Article: 218860 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <4ge3m113gs5l2bk9pfr7jalmk32r01ce94@4ax.com> <54h4m1hmsc2cl64evcupb4uoa74lf6v07c@4ax.com> Date: Fri, 28 Oct 2005 21:10:04 GMT On Fri, 28 Oct 2005 13:35:19 -0700, Richard Clark wrote: >The rejection is psychological, not actual. It is what I meant by >"mind-space." The vectors do not add up to zero, the mind simply >ignores the off-band content like you would at a party listening to >that cute office temp's whispers when your wife is yelling across the >room at you. > >Listen to a recording of that same scenario in mono and you WILL hear >your wife! > I understand the Bell Labs explored this effect (which they referred to as the "cocktail party effect") when exploring the nature of conversation for the purposes of novel approaches to telephony multiplexing. I don't think they developed a technology solution to exploit the cocktail party effect, but they did incorporate their knowledge of the statistical / syllabic / sentence characteristics in their Time Assignment Speech Interpolation (TASI) equipments, and TASI was quite successful. I think the term we would use for the cocktail party effect on a phone channel is "a crossed line", and you may be right in that the loss of spatial information because of the mono channel may have been the reason it didn't work. -- Article: 218861 of rec.radio.amateur.antenna From: "Richard Fry" References: Subject: Re: Antenna gain question Date: Fri, 28 Oct 2005 16:50:35 -0500 Message-ID: <43629c72_4@newsfeed.slurp.net> "Ron" wrote > Assume an incoming rf signal has exactly the same strength in all 3 > dimensions i.e., completely omnidirectional. Question: would an antenna > having gain capture any more signal power than a completely > omnidirectional antenna with no gain? __________ Whatever the net field that arrives from the transmit antenna (whether or not the transmit antenna is omnidirectional), a receiving antenna having gain in the direction toward the transmit antenna will perform better than if it is omnidirectional. Part of the improvement is due to its added gain, and part due to interference rejection from co- and adjacent-channel signals arriving from directions where the receiving antenna has less gain than an omni antenna. RF Article: 218862 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Antenna gain question Message-ID: References: Date: Fri, 28 Oct 2005 22:11:14 GMT On Fri, 28 Oct 2005 20:37:07 GMT, Ron wrote: >Assume an incoming rf signal has exactly the same strength in all 3 >dimensions i.e., completely omnidirectional. Question: would an >antenna having gain capture any more signal power than a completely >omnidirectional antenna with no gain? Your scenario is a little confusing. Here are my thoughts: I we took the case of say, noise that was sourced from all around you (that is not to mean an isotropic transmitter antenna), a directional antenna would receive about the same power as an isotropic antenna, and the difference would be due to antenna losses, ground reflection losses (if relevant). Galactic noise on HF might nearly fit into that scenario (or perhaps more topically, neighbourhood BPL interference), and I would expect that a 8dB yagi would receive similar power to a half wave dipole. Galactic noise is a little lower at the galactic poles, so in sweeping the yagi you may observe a very small directional effect. Further, ground reflection and different antenna + feed losses will introduce small differences. If at the end of that, you are trying to rationalise why a beam is better than a dipole, although the beam does not receive more or less of the "directionless" noise, it does increase the receive power from noise, interference and signal from the main beam direction and reduce receive power from noise and interference from away from the main beam. Does that hang together? Owen -- Article: 218863 of rec.radio.amateur.antenna From: Telamon Subject: Re: Tech Opinion Needed: Roof mounted AM/FM Auto Antenna References: <1130464885.459449.171250@g44g2000cwa.googlegroups.com> <1130530173.541787.323700@g47g2000cwa.googlegroups.com> Message-ID: Date: Fri, 28 Oct 2005 22:40:21 GMT In article <1130530173.541787.323700@g47g2000cwa.googlegroups.com>, "tsterkel" wrote: > I have a VW Jetta with the "shorty" antenna. I am pleasantly impressed > that it works better than the long steel type. The active (electronic) > antenna is superior, and I get reception when no one else can. > > Here is my question for the techys: > > I am looking at getting an Avanti. The shorty antenna would look very > rakish, and a nice replacement for that stock extended steel. The body > on the Avanti is Fiberglass. > > 1. Do you ground back to the frame? > 2. I suspect that the shorty antenna uses the metal roof as a ground > plane, true? > 3. If true, what is the implications for using the shorty, active > antenna on the fiberglass? > 4. What are the different model names/numbers for such an antenna, and > what is YOUR OPINION of each? Concerning #1, 2 and 3: Chances are it needs a ground plane of some sort around it. You could make a ground plane for it by using self sticking copper foil on the inside of the fiberglass panel the antenna is mounted on. The foil should extend some distance from the edge of the mounting hole for the antenna in all directions and then use a metal washer inside the panel to mount the antenna with, which will make contact with foil. -- Telamon Ventura, California Article: 218864 of rec.radio.amateur.antenna From: "Jerry Martes" References: <1130464885.459449.171250@g44g2000cwa.googlegroups.com> <1130530173.541787.323700@g47g2000cwa.googlegroups.com> Subject: Re: Tech Opinion Needed: Roof mounted AM/FM Auto Antenna Message-ID: Date: Fri, 28 Oct 2005 22:57:27 GMT "tsterkel" wrote in message news:1130530173.541787.323700@g47g2000cwa.googlegroups.com... >I have a VW Jetta with the "shorty" antenna. I am pleasantly impressed > that it works better than the long steel type. The active (electronic) > antenna is superior, and I get reception when no one else can. > > Here is my question for the techys: > > I am looking at getting an Avanti. The shorty antenna would look very > rakish, and a nice replacement for that stock extended steel. The body > on the Avanti is Fiberglass. > > 1. Do you ground back to the frame? > 2. I suspect that the shorty antenna uses the metal roof as a ground > plane, true? > 3. If true, what is the implications for using the shorty, active > antenna on the fiberglass? > 4. What are the different model names/numbers for such an antenna, and > what is YOUR OPINION of each? > > URLs appreciated > > thanks! > terry Hi Terry I find it difficult to think of the whip for AM radio reception on a car as 'the antenna'. It is more like a probe of the currents flowing on the outer surface of the car. The "shortys" on cars with amplifiers mounted at their base certainly arent antennas. A plastic car provides the Shorty with an environment thats considerably different from that anticipated by the original Shorty design. A strap to the chassis might be a solution for installing a VW amplified antenna. But,would you consider a radio intended for a Corvette?? Jerry Article: 218865 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna gain question Date: Fri, 28 Oct 2005 16:51:43 -0700 Message-ID: <11m5ecibpvtlm5d@corp.supernews.com> References: Ron wrote: > Assume an incoming rf signal has exactly the same strength in all 3 > dimensions i.e., completely omnidirectional. Question: would an antenna > having gain capture any more signal power than a completely > omnidirectional antenna with no gain? > > Ron, W4TQT Yes. The amount of signal "captured" from a given direction is exactly proportional to the gain in that direction. "Capture area", "effective aperture" and "gain" are simply different ways of expressing the same thing, as long as perfect efficiency is assumed; if you know any one you know the other two. Roy Lewallen, W7EL Article: 218866 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna gain question References: Message-ID: Date: Fri, 28 Oct 2005 23:57:45 GMT Ron wrote: > Assume an incoming rf signal has exactly the same strength in all 3 > dimensions i.e., completely omnidirectional. Question: would an antenna > having gain capture any more signal power than a completely > omnidirectional antenna with no gain? Does a vertical Yagi receive more signal than a vertical monopole? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218867 of rec.radio.amateur.antenna From: Ron Subject: Re: Antenna gain question References: Message-ID: Date: Sat, 29 Oct 2005 00:21:02 GMT Maybe I should restate my question. Assume a receiving antenna is in the center of a sphere and the received signal is coming in equal amounts from all points on the surface of the sphere. Which receiving antenna would capture more power, an omni or a high gain beam? There are no noise and no losses. Ron Ron wrote: > Assume an incoming rf signal has exactly the same strength in all 3 > dimensions i.e., completely omnidirectional. Question: would an antenna > having gain capture any more signal power than a completely > omnidirectional antenna with no gain? > > Ron, W4TQT > Article: 218868 of rec.radio.amateur.antenna From: "J. Mc Laughlin" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Fri, 28 Oct 2005 21:27:10 -0400 Message-ID: <11m5juvgvol5l3d@corp.supernews.com> References: <7l2ml1p4e9mjunf4ho30hd6uoj4e25756q@4ax.com> <1130172617.761487.141900@g14g2000cwa.googlegroups.com> <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> To emphasize one idea that Richard Clark has presented: Here is a direct quote from page 6-1 (section 6.2) of the chapter on loop antennas in the (first edition) Antenna Engineering Handbook edited by Jasik (1961): "The radiation pattern of a small loop is identical with that of a small dipole oriented normal to the plane of the loop with the E and H fields interchanged." The use of "magnetic" or other buzz words notwithstanding, a small loop is the dual of a small dipole. Practical considerations might cause one to select a small loop over a small dipole. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: JCM@Power-Net.Net Article: 218869 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna gain question References: Message-ID: Date: Sat, 29 Oct 2005 06:45:50 GMT Ron wrote: > Maybe I should restate my question. Assume a receiving antenna is in the > center of a sphere and the received signal is coming in equal amounts > from all points on the surface of the sphere. Are you trying to receive the background radiation left over >from the big bang? That's the only source outside of the sphere that I know of that can accomplish your boundary condition. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218870 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Sat, 29 Oct 2005 07:55:07 +0000 (UTC) Message-ID: References: <1130172617.761487.141900@g14g2000cwa.googlegroups.com> <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <11m5juvgvol5l3d@corp.supernews.com> wrote > I ran some estimates earlier of a much smaller multiturn look with > smaller wire. The Q held up much better than I expected and I'm also > considering smaller diameter multiturn loops. > ======================================== With multi-turn loops don't be tempted to neglect wire diameter. And it's well worth while spacing the wires by 1 or 2 wire diameters. Spaced wires reduce RF proximity-effect loss and increase Q. Neatness of construction is of little consequence. Wires need be supported only at the corners of the loop. Keep wires taut enough to prevent them flopping about in the wind. Electrically isolate the main loop. Don't connect it to anything. It will then maintain its good directional properties including its sharp null. Don't even think about screening or shielding the loop. It will serve no useful electrical purpose. It will cause proximity effect to reappear. Connect the smaller coupling loop to the unbalanced receiver via a thin twisted pair of whatever length you like without fear of it picking up any signal of consequence. Remember sensitivity depends ONLY on the enclosed loop area and NOT on the number of turns. So don't be tempted to reduce loop size just because it is multi-turned. Big signals never did anybody any harm. Whereas . . . . . ! I assume your QTH is not adjacent to WWV's antenna. ;o) ---- Reg, G4FGQ. Article: 218871 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Antenna gain question Date: Sat, 29 Oct 2005 01:32:48 -0700 Message-ID: <11m6ctlaj9568f9@corp.supernews.com> References: Ron wrote: > Maybe I should restate my question. Assume a receiving antenna is in the > center of a sphere and the received signal is coming in equal amounts > from all points on the surface of the sphere. Which receiving antenna > would capture more power, an omni or a high gain beam? There are no > noise and no losses. They'll intercept equal amounts, assuming both are lossless. The directional antenna will intercept a larger fraction than the isotropic antenna in the directions it favors, and less in others. The total will be be the same. In reverse, this is equivalent to calculating the average gain of the antennas, which is the same for all lossless antennas. Roy Lewallen, W7EL Article: 218872 of rec.radio.amateur.antenna From: "harrogate2" References: <1130464885.459449.171250@g44g2000cwa.googlegroups.com> <1130530173.541787.323700@g47g2000cwa.googlegroups.com> Subject: Re: Tech Opinion Needed: Roof mounted AM/FM Auto Antenna Message-ID: Date: Sat, 29 Oct 2005 08:59:17 GMT You only need a ground plane if the aerial transmits - for a receive only you can kust mount it, end of story. It is NOT a good idea to connect an earth bond at the aerial end as the aerial cable and that bond might provide a lower resistance feed to other vehicle electrics than the designed route and end up causing severe interference. -- Woody harrogate2 at ntlworld dot com Article: 218873 of rec.radio.amateur.antenna From: Ron Subject: Re: Antenna gain question References: Message-ID: <_TJ8f.87$0D4.47753@twister.southeast.rr.com> Date: Sat, 29 Oct 2005 12:26:34 GMT No, I'm just trying to understand antenna gain. Ron Cecil Moore wrote: > Ron wrote: > >> Maybe I should restate my question. Assume a receiving antenna is in >> the center of a sphere and the received signal is coming in equal >> amounts from all points on the surface of the sphere. > > Are you trying to receive the background radiation left over > from the big bang? That's the only source outside of the > sphere that I know of that can accomplish your boundary > condition. Article: 218874 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: antenna wire cleanup question Date: Sat, 29 Oct 2005 15:19:11 -0000 Message-ID: <11m74nfsl0k2l20@corp.supernews.com> References: > vinegar and salt should make quick work of it... neutralize with > baking soda or just rinse really well. Another excellent tarnish-remover for copper, brass, and silver can be made from baking soda and ammonia water, both available from any decent supermarket. Takes off the tarnished surface almost instantly, leaving clean bare metal, and rinses clean with water. -- 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: 218875 of rec.radio.amateur.antenna From: "Frank's" References: <436125c1$0$1163$5402220f@news.sunrise.ch> <4361ed77$0$1153$5402220f@news.sunrise.ch> Subject: Re: Problem with nec2 Message-ID: Date: Sat, 29 Oct 2005 15:41:09 GMT .......................... > >> If I calculate the gain with the formula: > >> > >> 4 * Pi * r^2 * |E|^2 > >> Gain = ----------------------- > >> P_in * 2 * 120 * Pi > >> > >> by using the E-Field magnitude values from nec2's output I get also > >> those very high values. (?) > > > PS, also confused by your formula. Which Value of E are you using? Are you > The formula should be correct: > I just use the magnitude value of the E Field. The intensitiy > W_rad is then 0.5 * |E|^2 / Z_w (E and H are in phase and > orthogonal in the far field) > > The radiation density U is then r^2 * W_rad (Unit: Watt per solid angle) > > The radiation density U_0 of an isotropic radiator with a total radiated > power P_rad is: P_rad / (4 * Pi). > > The gain is then U/U_0 (or in dBi: 10*log(U/U_0) ). Ok, now I understand. > > trying to calculate the "Total radiated power" (TRP)? If so you need to > > integrate the power density over a spherical region. The calculation is > Yes, but nec2 shows the total radiated power in its output. Have checked "Power Budget" output, and confirm that using it for TRP is valid in free space only. > No thats no true. In the output file I can see E_phi as well as E_theta for > every combination of phi and theta (for every frequency). I agree, my problem is that NEC-Win Pro cannot use this information for its graphical utilities. > I use the programm Xnecview to view the pattern and it has problems if you > don't have points over the full sphere. Ok, I see that Xnecview will only run under Linux/Unix OS. My version of NEC only runs in Windows. > > is that I normally do not use gain averaging. Also using 1 degree > The average gain (over the full sphere) should probably be 1 (or 0 dBi). > I get 0.991. Regards, Frank Article: 218876 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Antenna gain question Date: Sat, 29 Oct 2005 10:37:54 -0500 Message-ID: <8129-43639752-515@storefull-3253.bay.webtv.net> References: Ron, W4TQT wrote: "Question: would an antenna having gain capture any more signal than a completely omnidirectional antenna with no gain?" Directive gain depends entirely on the distribution of radiated power. See 1955 Terman page 870. The antenna gain figure is identical for transmitting or receiving. To take full advantage of gain in a line of sight path, the electric vector must be parallel with that received. Cross polarization can cause up to almost 30 dB signal loss. There are directional antennas that receive vertical and horizontal polarizations equally well. Yes. An antenna with gain captures more signal than an antenna with no gain when both are in their best positions and equally distant fron the same signal source. Best regards, Richard Harrison, KB5WZI Article: 218877 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: A few Helical Antenna question References: Message-ID: Date: Sat, 29 Oct 2005 11:56:10 -0500 Dale Parfitt wrote: >"Chris W" <1qazse4@cox.net> wrote in message >news:ku88f.1019$ZP1.519@dukeread11... > > >>Dale Parfitt wrote: >> >> >> >>>>PS I would like to build 2 of these one is for 2.4ghz wireless network >>>> >>>> >>>>and one is 432 mhz amateur band EME and or satellite work. So the 2.4ghz >>>>version will likely never see more than 100 mW but could see as much as 1 >>>>watt. The 432 mhz version could see as much as 1000 watts, but if I did >>>>that it would be to an array of 4 of them so I guess each one would only >>>>see 250 watts? >>>> >>>>-- >>>>Chris W >>>> >>>> >>>> >>>> >>>EME on 432 is linearly polarized (although switching polarities to make >>>up for Faraday rotation can be advantageous) - you'll be throwing away a >>>huge 3dB, have higher sidelobes than a well designed Yagi (nullifying the >>>low sky temp advantage of deep space) and less gain per boom length than >>>a good Yagi- all in all, a dismal choice for EME. >>> >>>Dale W4OP >>> >>> >>> >>> >>The calculation in the ARRL Antenna book say that a 12 foot boom with a >>circumference of 1.33 wavelengths will give me a 19.9 dbi gain this should >>make up for the 3 db loss I think. I haven't seen a yagi that gives that >>much gain in with a 12 foot boom. The book also says that the side lobe >>problem can be significantly reduced by creating an array of 4 helical >>antennas. That should up the gain to 25.9 db. That's pretty good for EME >>isn't it? Take it to 16 and you get over 30 db gain. And the only need >>to be spaced at 1.5 wavelengths, that's only 3.4 feet. >> >>-- >>Chris W >> >> > >The closest optimized Yagi I found was a K1FO on a 14' boom- 17.9dBi which >compares quite well with your 19.9dBi on a 12' boom once we adjust for the >polarization loss making the helical 16.9dBi linear for the helix vs. 17.9dB >for the K1FO My experience with EME is at 23cM where we use dishes- but I >can tell you that 1dB is to kill for.. >The circularity could be an advantage as it would be insensitive to Faraday. >Another advantage is that they are non critical to build- at least from a >gain standpoint. But I think the real issue will be weight and weight >ditribution. Between the helical tubing, non conductive boom and the >reflector screen a helix is going to be a clydesdale compared to a Yagi. >Another problem might be the necessity to mount the array from behind the >reflector- that's going to be quite a moment arm. > >Bottom line is, 432 MHz EME is well explored- I am not aware of the use of >helices for EME there- although, again I am not active on 432 EME. If they >are not being use, there's probably a reason. > >Dale W4OP > > I guess unless both stations were using a helical antenna, an array of yagies would be better. Since the helical antennas would have to have opposite polarization, that would be pretty inconvenient unless both stations had an array of RH for TX and LH for RX, in which case you would have to build twice as many antennas. I did have an idea for mounting them though. I was going to find something to use as a form to wrap the helix around and then cover it with fiberglass, making a big fiberglass tube, then remove the mold from the inside. I think that would make for a pretty strong and lite structure. I would then make some kind of fiberglass structure to mount the antenna at it's CG. Of course such an antenna would have a pretty high wind load, so you would need a way to easily take it down in case of high winds. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218878 of rec.radio.amateur.antenna From: "Mr. Man with the Master Plan" References: <1129872363.320801.40130@g49g2000cwa.googlegroups.com> Subject: Re: 2.4 gHz transmitter Message-ID: <64O8f.17985$rE2.17565@fe10.lga> Date: Sat, 29 Oct 2005 13:11:48 -0400 radioshack and put it up really really high!!! -MMWTMP "oldcrow" wrote in message news:1129872363.320801.40130@g49g2000cwa.googlegroups.com... > Hi: > > Can anyone put me on as to where I may purchase a small 2.4 gHz > transmitter for sending video from about 1/2 mile. > > Bob > Article: 218879 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna gain question References: <8129-43639752-515@storefull-3253.bay.webtv.net> Message-ID: Date: Sat, 29 Oct 2005 18:06:11 GMT Richard Harrison wrote: > Yes. An antenna with gain captures more signal than an antenna with no > gain when both are in their best positions and equally distant fron the > same signal source. This thread has got me wondering. Which antenna would capture more Big Bang Background Radiation? -- 73, Cecil http://www.qsl.net/w5dxp Article: 218880 of rec.radio.amateur.antenna From: "Dale Parfitt" References: Subject: Re: A few Helical Antenna question Message-ID: Date: Sat, 29 Oct 2005 17:34:10 GMT "Chris W" <1qazse4@cox.net> wrote in message news:MQN8f.5728$ZP1.1737@dukeread11... > Dale Parfitt wrote: > >>"Chris W" <1qazse4@cox.net> wrote in message >>news:ku88f.1019$ZP1.519@dukeread11... >> >>>Dale Parfitt wrote: >>> >>> >>>>>PS I would like to build 2 of these one is for 2.4ghz wireless network >>>>> >>>>>and one is 432 mhz amateur band EME and or satellite work. So the >>>>>2.4ghz version will likely never see more than 100 mW but could see as >>>>>much as 1 watt. The 432 mhz version could see as much as 1000 watts, >>>>>but if I did that it would be to an array of 4 of them so I guess each >>>>>one would only see 250 watts? >>>>> >>>>>-- >>>>>Chris W >>>>> >>>>> >>>>> >>>>EME on 432 is linearly polarized (although switching polarities to make >>>>up for Faraday rotation can be advantageous) - you'll be throwing away a >>>>huge 3dB, have higher sidelobes than a well designed Yagi (nullifying >>>>the low sky temp advantage of deep space) and less gain per boom length >>>>than a good Yagi- all in all, a dismal choice for EME. >>>> >>>>Dale W4OP >>>> >>>> >>>> >>>The calculation in the ARRL Antenna book say that a 12 foot boom with a >>>circumference of 1.33 wavelengths will give me a 19.9 dbi gain this >>>should make up for the 3 db loss I think. I haven't seen a yagi that >>>gives that much gain in with a 12 foot boom. The book also says that the >>>side lobe problem can be significantly reduced by creating an array of 4 >>>helical antennas. That should up the gain to 25.9 db. That's pretty >>>good for EME isn't it? Take it to 16 and you get over 30 db gain. And >>>the only need to be spaced at 1.5 wavelengths, that's only 3.4 feet. >>> >>>-- >>>Chris W >>> >> >>The closest optimized Yagi I found was a K1FO on a 14' boom- 17.9dBi >>which compares quite well with your 19.9dBi on a 12' boom once we adjust >>for the polarization loss making the helical 16.9dBi linear for the helix >>vs. 17.9dB for the K1FO My experience with EME is at 23cM where we use >>dishes- but I can tell you that 1dB is to kill for.. >>The circularity could be an advantage as it would be insensitive to >>Faraday. Another advantage is that they are non critical to build- at >>least from a gain standpoint. But I think the real issue will be weight >>and weight ditribution. Between the helical tubing, non conductive boom >>and the reflector screen a helix is going to be a clydesdale compared to a >>Yagi. >>Another problem might be the necessity to mount the array from behind the >>reflector- that's going to be quite a moment arm. >> >>Bottom line is, 432 MHz EME is well explored- I am not aware of the use of >>helices for EME there- although, again I am not active on 432 EME. If >>they are not being use, there's probably a reason. >> >>Dale W4OP > > I guess unless both stations were using a helical antenna, an array of > yagies would be better. Since the helical antennas would have to have > opposite polarization, that would be pretty inconvenient unless both > stations had an array of RH for TX and LH for RX, in which case you would > have to build twice as many antennas. > > I did have an idea for mounting them though. I was going to find > something to use as a form to wrap the helix around and then cover it with > fiberglass, making a big fiberglass tube, then remove the mold from the > inside. I think that would make for a pretty strong and lite structure. I > would then make some kind of fiberglass structure to mount the antenna at > it's CG. Of course such an antenna would have a pretty high wind load, so > you would need a way to easily take it down in case of high winds. > > -- > Chris W > Hi Chris, You're right on the polarity sense- it gets reversed upon lunar surface reflection. At 23cM we are using a scalar or septum horns that have 2 feedpoints- CW and CCW- much easier to to do with a horn as it only involves a 2nd orthogonal probe. A set of 4 capacity stubs arranged longitudinally along the guide generates the 2 senses. If you are seriously interested in EME- take alook at 23cM. Gain is easy to come by in the form of dishes; LNA NF are now in the <0.2dB and power from the GS series tubes and Mistubishi modules are stable and quite easy. Not unusual to hear SSB stations ragchewing on activity or contest weekends, no Faraday issues and lots of big gun activity. Dale W4OP Article: 218881 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Sat, 29 Oct 2005 20:38:23 +0000 (UTC) Message-ID: References: <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <11m5juvgvol5l3d@corp.supernews.com> <6ab7m1hulck0nf2oomgbc5gbv07n4j8lis@4ax.com> Trabem, I will try to answer your remaining questions in the order at which they occur. There must be a compromise between size of loop, receiving sensitivity, and the ability to rotate it. Only you can decide. I can suggest only that you bias your opinion towards size matters more than the ability to rotate the thing. Just make sure that the broadside null does not correspond to the direction from which your favourite transmissions come from. The receiving lobes in the polar diagram are very broad. The polar diagram is a figure of 8, like a pair of touching circles. You won't need Eznec. The impedance of the line from the coupling loop to the receiver doesn't matter two hoots. At 60 KHz it is just a pair of wires. A twisted pair of wires has an impedance of very roughly 130 ohms. But at 60 KHz the line length is so short in terms of wavelengths it doesn't matter what its impedance is. The coupling loop can be considered to be directly connected to the 50-ohm receiver. And even with an extremely long line any impedance mismatch loss will be negligible. So forget about 300-ohm balanced line and just use a simple not-tightly-twisted pair. NO IMPEDANCE MATCHING REQUIRED at either end. The size of the small coupling loop inside the main loop matches 50 ohms to a 50-ohm receiver. So ideally the line to the receiver could be 50-ohm coax. But, as I say, it doesn't matter. The size and shape of the small coupling loop is not critical. It can be circular or square. Theoretically, to match the loop to a 50-ohm receiver, it should have an area about 1/25th of the main loop area. To simplify construction the coupling loop can be made self-supporting. Electrically, the thickness of the wire in the coupling loop need be no greater than the wire in the line which connects it to the receiver. The only wire diameter which matters is that of the main loop itself. As the spacing between wires on the main loop increases the RF proximity loss in the loop conductor (related to skin effect) decreases and Q increases. But other things happen when the width of the loop increases with spacing. For example, loop inductance decreases. We are not comparing like with like. And in any case maximisation of Q is not the primary objective. There are other things to be considered. For example, if you want to increase Q then don't bother to increase spacing between turns, just increase wire diameter. But with given wire diameter, the optimum spacing between the wire centres of adjacent turns, to maximise Q, is very crudely about twice the wire diameter. But, as I say, it is very non-critical and you might be better off by increasing wire diameter as it simplifies loop construction. Then, once again, you will have the option of increasing spacing between turns. Compromises are never ending. ;o) Whatever you end up with I can see from your enthusiasm you are enjoying your efforts and will continue to do so. ---- Reg, G4FGQ. ===================================== wrote in message news:6ab7m1hulck0nf2oomgbc5gbv07n4j8lis@4ax.com... > Hi REg, > > Looks like I have a plan for a new loop. > > New loop design: > > I have a plan for a more appropriately dimensioned loop. > > At 60 KHz, > > 4 turns of 2 mm diameter wire, spaced 4 wire diameters apart. > 2 meters per side > 123 uH, 60,000 pF to resonate > 4.7K across the loop. > 300 ohm feed impedance at single turn loop feed > Q (unloaded) = 101 > > This allows me to feed the loop with 300 ohm balanced line, which I > can easily transform to 50 ohms at the receiver. > > I'm not sure what the impedance of twisted wire is though, which would > be even cheaper than 300 ohm twin lead. > > Also, my Q will be slightly higher as I can stagger the turns some, so > that the wires won't run parallel to each other for the entire length. > > I was never quite thrilled with a big loop threaded through the trees > and supported in that manner, it makes it hard to rotate:>: Being able > to rotate the loop is a good thing:>: > > Is the 1 turn pick up loop critical??? > > And, I have another question....... > > I used rj2loop3 and ran the same numbers as above, except that I > separated the wires by 10 wire diameters instead of 4. > > Instead of seeing the Q improve, it was reduced (from 101) to 93. I > expected the Q to improve, not get worse. It seems odd to me. Is there > a good reason for this?? Ran it with a very low number and the Q also > get worse. So there appears to be an 'optimal' wire winding pitch for > optimizing Q? > > Byr the way, nice software package, thank you for it's use! > > >I assume your QTH is not adjacent to WWV's antenna. ;o) > > Temporarily, it is on the East Coast of the US. But, at home it is > high in the mountains in Northern EU (with no commercial power for > miles around). > > Thanks, > Article: 218882 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: White Space Message-ID: <1ho7m1dfu0t0cij1o93i3ibbjf55ni25o2@4ax.com> References: Date: Sat, 29 Oct 2005 21:03:18 GMT On Fri, 21 Oct 2005 19:05:16 -0700, Richard Clark wrote: >What do I imagine? Amateur TV Broadcasting! Remember the ill-fated >neighborhood FM? Interest groups sank that idea like a rock in the >ocean. What does "Amateur" mean in this context? Discard the notion >of transmitting only to exchange QSL cards and start pumping music and >game shows produced at the community level. The prohibition against >transmitting entertainment is a antediluvian appeal to the 1930s. >"Amateur" in this context means non-commercial. Not even appeals for >donations. Do it on your own or go back to vaudeville. > >My notion to re-invigorate Amateur radio is to expand neighborhood TV >transmission (small service area, AKA Pirate TV) making Hams the >non-profit extension of the FCC for site review and inspection. Boost >the technical requirements (sort of a low grade General >Radiotelephone) for non-profit transmission testing and monitoring. >Develop an association for granting area and frequency coverage (just >like repeater associations have been doing for years) to co-ordinate >allocations. There should even be provisions for networking. Somehow I think what industry has in mind are ways to tap into "unused spectrum space" dynamically and exploit it for Internet access services. You don't need to look very far into their proposed method of operation to see that a squat on a frequency band soon makes it unused by anyone else. Aren't the IEEE working on standards for such spectrum exploitation? These ideas share a bit in common with the BPL menace, uncoordinated access to spectrum, and put the onus on the licenced service subject to interference to follow a regulatory maze to regain access to their licence entitlements. Owen PS: "unused spectrum space" means not licenced to the squatter, and not carrying enduring signals sufficient in strength to interfere with their squat. -- Article: 218883 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Message-ID: References: <4ge3m113gs5l2bk9pfr7jalmk32r01ce94@4ax.com> <54h4m1hmsc2cl64evcupb4uoa74lf6v07c@4ax.com> <9115m15iqhe74025ikjp6s1titp638oe7u@4ax.com> Date: Sat, 29 Oct 2005 21:36:07 GMT On Fri, 28 Oct 2005 13:45:17 -0700, Richard Clark wrote: >On Fri, 28 Oct 2005 20:12:48 GMT, Owen Duffy wrote: > >>Didn't Don Stoner describe a synchronous detector way back. I think I >>remember reading an article in the mid sixties in "The Sideband >>Handbook" or similar. >> >>I was about 15 then, so a detector that had something like 17 bottles >>in it seemed overkill when I was copying CW and SSB on an AM receiver >>(ie diode detector) with BFO. >> >>The appeal being an all-mode detector (including DSBSC), but >>synchrounous detectors didn't seem to catch on in comms receivers, >>well not until DSP detection... well I don't recall coming across them >>anyway. > >Hi Owen, > >17 bottles indeed. That seems to strike a resonant chord in the >ganglia because my construction was on a utility box of about 3" x 9" >x 15" (not counting power supply requirements). We were working from >a printed article certainly; and to confirm your recollection, there >was a list of modes that could be detected that was long. > >My perception of the resurgence of interest in synchronous detection >(it seems to have many names) is that a considerable body of knowledge >evaporated in the 70s and 80s to leave only fragments of what this >detector was useful at. I think the appeal of it in the early days of suppressed carrier exploitation by amateurs lay in its application to DSBSC demodulation. It probably fell by the wayside when filter method SSB transceivers became lower in cost. Here is an interesting hypothetical. Australian amateurs at the unrestricted licence grade are subject to the following power restrictions: 16 Transmitter output power (1) Subject to section 15, the licensee must not operate an amateur unrestricted station, using a transmitter output power of more than 400 watts pX, if the emission mode of the station includes: (a) C3F; or (b) J3E; or (c) R3E. (2) The licensee must not operate an amateur unrestricted station, with an emission mode not mentioned in subsection (1), using a transmitter output power of more than 120 watts pY. Since the emission mode for DSBSC is not one of those mentioned in 16(1), then the power limit is 120W pY. If the pX/pY (PEP/Average) power ratio for radiotelephony is somewhere around 12dB to 15dB, that suggests that (using a worst case of 15dB) that the 120W pY DSBSC telephony transmitter is around 3800W pX (PEP), whereas you will note that if we use SSBSC (J3E) we are limited to 400W pX. Doesn't make sense, does it. Did I get the maths wrong? Owen -- Article: 218884 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Antenna gain question Message-ID: <6sq7m1ph6m9gq61upli1pds1g7po4ml0l3@4ax.com> References: <1130620682.540158.307160@f14g2000cwb.googlegroups.com> Date: Sat, 29 Oct 2005 21:37:43 GMT On 29 Oct 2005 14:18:02 -0700, "K7ITM" wrote: >Do all (assume lossless) antennas with the SAME directionality caputre >the same signal power? Is "directionality" equivalent to the well known term Directivity? Owen -- Article: 218885 of rec.radio.amateur.antenna From: Polymath Subject: Re: Strictly OT - but you wouldn't expect anythiing else - would you? Date: Sat, 29 Oct 2005 17:51:23 -0400 Message-ID: Stop forging me, asshole! "Polymath" wrote: > BRIAN! M3/CB Fools' candidate for you!!!!! > > Hugh Moore wrote: > > CQ the brains in this group, > > I ask coz I ain't got nun gov! > G4SDW _________________________________________ Usenet Zone Free Binaries Usenet Server More than 140,000 groups Unlimited download http://www.usenetzone.com to open account Article: 218886 of rec.radio.amateur.antenna From: "Hugh Moore" Subject: Re: Strictly OT - but you wouldn't expect anythiing else - would you? Date: Sat, 29 Oct 2005 23:17:37 +0100 Message-ID: References: >> Stop forging me, asshole! Why would anyone want to forge YOU? or your ASSHOLE?? Dummy / pram / throw / out - reassemble ! - NO absolutely NO PRIZES Oh dear Hugh Article: 218887 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: antenna lengths Date: Sat, 29 Oct 2005 22:31:04 +0000 (UTC) Message-ID: References: "Reg Edwards" wrote > To calculate change in velocity due to plastic PVC insulation we need > to know :- > > Wire diameter = d > Diameter over insulation = D > Height of wire above ground = H > Permittivity of insulating material = K > > First calculate capacitance of bare wire to ground. > Then calculate capacitance of insulated wire to ground. > Velocity Factor = SquareRoot of their ratio. > Neither Terman's nor Kraus' Bibles will mention the following > formulae. So you'll just have to take my word for it. > > > Velocity Factor = SquareRoot( ( A + B ) / C ) > > Where - > > A = K * Ln( 4 * H / D ) > > B = Ln( D / d ) > > C = K * Ln( 4 * H / d ) > > Example : > Bare wire diameter = 1.6 mm = 14 awg. > Diameter over insulation = 2.6 mm. > Height above ground = 10 metres = 33 feet. > Permittivity of insulation = 3.5 > > Velocity factor = 0.983 > Or a decrease in resonant frequency of 1.7 percent which can nearly > always be forgotten about. > > The electrical effect of the enamel on magnet wire is entirely > negligible. But it does protect the wire from atmospheric pollution. ======================================== After a couple of days, and the time it took to derive the equations, does nobody want to argue about it ? What about you, my dear Richard Clark ? By the way, I have now reverted to Australian, Banrock Station red plonk as being the best buy in my local supermarket. To get into my glass it has to come 12,000 miles. But, like it or not, our small globe gets smaller day by day. ---- Reg, G4FGQ. Article: 218888 of rec.radio.amateur.antenna Subject: Question on shooting a line From: Ed Message-ID: Date: Sat, 29 Oct 2005 22:55:15 GMT I'm trying to shoot a line over a tree limb to hoist my next generation of wire dipole. I'm using a slingshot, a 1 oz round lead fishing weight, and in this case, 40# test fishing line. Although I have had fair success in the past, I'm having difficulties lately. My weight won't pull the line down the other side of the limb beyond where it stopped. My Question: What weight do you guys recommend? Does anyone know what weight is used on the EZhang system? Comments sollicited. Right now I'm waiting for the wind to blow and hopefully move the tree limb enough to make the hanging weight pull my live over to the point where I can reach it. Ed K7AAT Article: 218889 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: White Space Message-ID: References: <1ho7m1dfu0t0cij1o93i3ibbjf55ni25o2@4ax.com> Date: Sat, 29 Oct 2005 23:09:50 GMT On Sat, 29 Oct 2005 15:50:12 -0700, Richard Clark wrote: >On Sat, 29 Oct 2005 21:03:18 GMT, Owen Duffy wrote: > >>Aren't the IEEE working on standards for such spectrum exploitation? > >Hi Owen, > >If they have, the filaments' light of their finals are hidden under a >bushel. > http://standards.ieee.org/announcements/pr_80222.html Owen -- Article: 218890 of rec.radio.amateur.antenna From: "Charlie" Subject: Re: New to VHF/UHF Date: Sat, 29 Oct 2005 18:37:29 -0500 Message-ID: <11m81u6krouga7b@news.supernews.com> References: <11m7p8f25vmfg1b@corp.supernews.com> Using an Icom 746 Pro here which includes HF/6M/2M with a full 100W on all bands. I have been on HF since 1995 and an avid DX'r and secretly sneered at VHF/UHF but did want to try 2M SSB. I now have VHF antennas at 72' 90' and 95' and am net control and founder of the Deep South 2 Meter SSB Net. There was very little 2M SSB traffic in my region when I got on 2M SSB but since the net started on April 8, 2005 we have now had over 100 2M SSB stations check-in representing 10 states so far. Typically there are 25-35 or more O(record is 39) check-ins every evening. So..for those that say there is little 2M SSB activity why not stir some up???!!!??? Deep South 2 Meter SSB Net - 8:30PM CT - 144.240 USB - net control EM52kn (Union,Mississippi) www.deepsouthnet.net -- Charlie-AD5TH www.ad5th.com "Rod Maupin" wrote in message news:11m7p8f25vmfg1b@corp.supernews.com... > I've been on HF for years, but am new to VHF/UHF. > > I'm thinking of getting a VHF/UHF base station and it looks like the only > thing around is the ICOM IC-910H. Is there a reason for this? Because of > this, it seems to me that most people must not have a base station for > these bands. > > Is this correct? > > Rod > > Article: 218891 of rec.radio.amateur.antenna Subject: Re: Question on shooting a line From: Ed References: Message-ID: Date: Sun, 30 Oct 2005 00:29:25 GMT Addendum to first post: a couple hours later: It didn't take a light breeze more than an hour or so to wiggle the tree limb and allow the weight to drop down a bit further. I grabbed it with a pole and have completed that phase now. But my question still stands. What is the recommended weight and line for this type work, and are there any recommended techniques to get the weight to drop down when friction of the tree limb tends to hold it? Ed K7AAT Article: 218892 of rec.radio.amateur.antenna From: "Hal Rosser" References: Subject: Re: Question on shooting a line Message-ID: Date: Sat, 29 Oct 2005 23:01:50 -0400 > I use 1/16" braided nylon (so no curl is built in). > > I've thrown it by hand (swinging the weight); > used a slingshot; > used a bow and arrow. > What - no potato-gun ?? conduit, hair-spray, and a potato with fishing line. spray into the conduit (closed at the other end except for a small hole.)) force potato into open end a ways. put a match to the small hole. ka-pow I heard it works pretty good, but sounds dangerous. I use bow-and-arrow - with a fishing arrow. that arrow is heavy enough to pull the line to the ground From /dev/null Sun Oct 30 09:16:23 EST 2005 Article: 218893 of rec.radio.amateur.antenna From: Barnacle Bill Newsgroups: rec.radio.amateur.antenna Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 03:29:48 -0000 Organization: Spouter Inn Gang Message-ID: <11m8fhc5lqvs6fe@corp.supernews.com> References: Reply-To: /dev/null User-Agent: slrn/0.9.8.1 (Linux) X-Complaints-To: abuse@supernews.com Lines: 4 Path: news1.isis.unc.edu!elk.ncren.net!logbridge.uoregon.edu!newsfeed.stanford.edu!sn-xit-03!sn-xit-08!sn-post-01!supernews.com!corp.supernews.com!not-for-mail Xref: news1.isis.unc.edu rec.radio.amateur.antenna:218893 On 2005-10-29, Reg Edwards wrote: > By the way, I have now reverted to Australian, Banrock Station red Yellow Tail Shiraz Article: 218894 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: SWR meter for 2.4ghz Message-ID: Date: Sat, 29 Oct 2005 23:27:13 -0500 Can someone tell me where I can get an SWR meter that will work in the 2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several websites that claim to tell you how to build your own, but none of them have anywhere enough information for someone who doesn't already know what they are doing. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218895 of rec.radio.amateur.antenna From: "Jerry Martes" References: Subject: Re: SWR meter for 2.4ghz Message-ID: Date: Sun, 30 Oct 2005 05:14:18 GMT "Chris W" <1qazse4@cox.net> wrote in message news:xYX8f.6376$ZP1.4994@dukeread11... > Can someone tell me where I can get an SWR meter that will work in the 2.4 > to 2.45 ghz range with 50 to 1000 mW? I have found several websites that > claim to tell you how to build your own, but none of them have anywhere > enough information for someone who doesn't already know what they are > doing. > -- > Chris W > > Gift Giving Made Easy > Get the gifts you want & give the gifts they want > One stop wish list for any gift, from anywhere, for any occasion! > http://thewishzone.com Hi Chris Could you get the information you need with a directional coupler?? eBay has directional couplers for less than $20.00 often. Jerry Article: 218896 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: SWR meter for 2.4ghz References: Message-ID: Date: Sun, 30 Oct 2005 00:35:44 -0500 Jerry Martes wrote: >"Chris W" <1qazse4@cox.net> wrote in message >news:xYX8f.6376$ZP1.4994@dukeread11... > > >>Can someone tell me where I can get an SWR meter that will work in the 2.4 >>to 2.45 ghz range with 50 to 1000 mW? I have found several websites that >>claim to tell you how to build your own, but none of them have anywhere >>enough information for someone who doesn't already know what they are >>doing. >>-- >>Chris W >> >>Gift Giving Made Easy >>Get the gifts you want & give the gifts they want >>One stop wish list for any gift, from anywhere, for any occasion! >>http://thewishzone.com >> >> > > Hi Chris > > Could you get the information you need with a directional coupler?? > > That is a good question. One site talked about using a directional coupler, a few diodes and a scope to measure SWR but I didn't really understand it all and it sounded like I needed a special diode that they didn't give details on where to get. What I am trying to do is tune home made antennas for wireless networks. So I need to measure the SWR so I know when the antenna is tunned as good as I can get it. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218897 of rec.radio.amateur.antenna From: "Jerry Martes" References: Subject: Re: SWR meter for 2.4ghz Message-ID: Date: Sun, 30 Oct 2005 05:59:52 GMT "Chris W" <1qazse4@cox.net> wrote in message news:LYY8f.6458$ZP1.6257@dukeread11... > Jerry Martes wrote: > >>"Chris W" <1qazse4@cox.net> wrote in message >>news:xYX8f.6376$ZP1.4994@dukeread11... >> >>>Can someone tell me where I can get an SWR meter that will work in the >>>2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several websites >>>that claim to tell you how to build your own, but none of them have >>>anywhere enough information for someone who doesn't already know what >>>they are doing. >>>-- >>>Chris W >>> >>>Gift Giving Made Easy >>>Get the gifts you want & give the gifts they want >>>One stop wish list for any gift, from anywhere, for any occasion! >>>http://thewishzone.com >>> >> >> Hi Chris >> >> Could you get the information you need with a directional coupler?? > > That is a good question. One site talked about using a directional > coupler, a few diodes and a scope to measure SWR but I didn't really > understand it all and it sounded like I needed a special diode that they > didn't give details on where to get. > What I am trying to do is tune home made antennas for wireless networks. > So I need to measure the SWR so I know when the antenna is tunned as good > as I can get it. > > -- > Chris W > > Gift Giving Made Easy > Get the gifts you want & give the gifts they want > One stop wish list for any gift, from anywhere, for any occasion! > http://thewishzone.com Hi Chris If you are lucky, you will get some response to your post from some of the very sharp antenna guys here. I'm not one of them. I personally would have alot of learning to do if I wanted to know how to *match* an antenna if I knew only VSWR. I need to know the actual impedance at the load. I have built a crude slotted line so I can measure complex load impedances at 137 MHz. That works OK, but certainly not perfect. Let me know if you have access to tools that you can use to build a slotted line for 2.4 GHz.. A slotted line makes impedance matching fairly easy. I suspect there are better ways to measure load impedance than building slotted lines for 2.4 GHz, I just dont yet understand them. Jerry Article: 218898 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Question on shooting a line Date: Sun, 30 Oct 2005 03:43:15 -0800 Message-ID: <11m9ceqjqnbs59b@corp.supernews.com> References: I've been doing this on Field Day for a long time. First off, I use about 6-8 pound test line. It's heavy enough to pull a nylon cord back over the tree, but light enough so it comes off smoothly and so I can get plenty of line on a reel. Second, I use teardrop-shaped fishing weights (narrow at the line end), never round or pyramid. The latter types snag too readily if you have to pull the weight back up. Try dragging the weight across a weedy back yard if you need an illustration. As for the weight itself -- over the years I slowly increased the weight to as much as 3 ounces, so it would drop freely through fairly dense pine and fir trees. But I had an increasing amount of trouble with the weight coming out of the pouch during the shot, leading to very short shots and even occasionally a cut elastic unless everything was just right. Dropping back with the weight cured the shooting problem, along with using a slingshot with wide spaced arms. I've settled on about 2 oz as the best compromise between trouble-free shooting and the ability to drop through the tree. I never use this method for a home installation unless it's for no more than a few days -- the twine or even rope cuts into the tree, making it impossible to get down. This might not be as much of a problem with hardwood trees as it is for softer and pitchier conifers. Also, I've had people tell me that very heavy nylon monofilament is less prone to this -- I haven't tried it. Roy Lewallen, W7EL Ed wrote: > I'm trying to shoot a line over a tree limb to hoist my next > generation of wire dipole. > > I'm using a slingshot, a 1 oz round lead fishing weight, and in this > case, 40# test fishing line. > > Although I have had fair success in the past, I'm having difficulties > lately. My weight won't pull the line down the other side of the limb > beyond where it stopped. > > My Question: What weight do you guys recommend? Does anyone know > what weight is used on the EZhang system? Comments sollicited. > > Right now I'm waiting for the wind to blow and hopefully move the tree > limb enough to make the hanging weight pull my live over to the point > where I can reach it. > > > Ed K7AAT Article: 218899 of rec.radio.amateur.antenna From: "Frank" References: Subject: Re: SWR meter for 2.4ghz Message-ID: Date: Sun, 30 Oct 2005 13:31:10 GMT > Can someone tell me where I can get an SWR meter that will work in the 2.4 > to 2.45 ghz range with 50 to 1000 mW? I have found several websites that > claim to tell you how to build your own, but none of them have anywhere > enough information for someone who doesn't already know what they are > doing. > -- > Chris W I would recommend the Mini-Circuits ZABDC-25HP directional coupler ($89.95). Do not use diode detectors. Mix the forward and reverse ports down to a low frequency, of 10 MHz or so (phase information is preserved). View the downconveted signals on a dual channel oscilloscope. Techincally you need to low pass filter the downconverted signals, but the scope will not see the higher frequency components. Do not attempt to use SO-239 connectors at 2.5 GHz. Building a directional coupler at 2.5 GHz requires track precision in the order of +/- 1/1000". You will also need high quality PCB material such as RT Duroid. Regards, Frank Article: 218900 of rec.radio.amateur.antenna From: "Steve - www.ukspeedtraps.co.uk" Subject: Backpack Antenna, help please Date: Sun, 30 Oct 2005 14:27:49 +0000 (UTC) Message-ID: Hi All I want to construct a backpack antenna that can be left on my rucksack and used when walking. The plan is to have a FT817 on my waist and the antenna fitted to the rucksack. I been playing with a mobile antenna today and can not get the SWR down without trailing a wire. I don't want a wire trailing behind me. Any ideas for a 2m antenna that can be left on a rucksack when walking and used for transmittion. Height is not a major problem but it has to realistic and robust. Thanks Steve -- The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk The UK Weather Guide" @ www.ukstorms.com Article: 218901 of rec.radio.amateur.antenna From: "Earl Needham" Subject: MasterMobile wanted Date: Sun, 30 Oct 2005 07:34:51 -0700 Message-ID: <11m9mged7ckqrcc@corp.supernews.com> Looking for one MasterMobile 20-meter coil and one MasterMobile 75-meter coil. Thanks, Earl -- Earl Needham Clovis, New Mexico USA Article: 218902 of rec.radio.amateur.antenna From: "John N9JG" Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Sun, 30 Oct 2005 09:41:17 -0500 Message-ID: References: <1130257330.949208.135330@o13g2000cwo.googlegroups.com> <8mgtl19fg7lbtc4titunm4vggfcqv72uem@4ax.com> <1130286662.633940.114410@g47g2000cwa.googlegroups.com> <11m5juvgvol5l3d@corp.supernews.com> <6ab7m1hulck0nf2oomgbc5gbv07n4j8lis@4ax.com> Take a look in the latest issue of the ARRL Antenna Book. Chapter 5 is devoted entirely to loop antennas, and the chapter includes information about small loops. At the end of the chapter is a nice sized bibliography. wrote in message news:qam8m1dj5402c0r83dt1tmjt9bc061tf3i@4ax.com... [stuff] > > Getting back to last nights study session. Spent a couple of hours in > my 1987 ARRL Handbook and the remainder on the web looking at real > life loops published there. The web aspect was really disappointingly > devoid of technical jargon, it seems like most of the loop authors > just threw something up and it seemed to work-the end:>: Do people > just throw stuff up without understanding what they're doing, or do > they understand and just fail to document the theory?? > > The Handbook tour was almost as bad. Very little was said about loops > except that which applied to the full wave resonant loop and how it > can serve as a driven element in a 1 lambda 'guad' type radiator. > Other than the theoretical wavelength, the correction factor for wire > diameter, there was not more than 2 paragraphs written with useful > information on short loops such as I am trying to put up. > [stuff] Article: 218903 of rec.radio.amateur.antenna From: "Fred W4JLE" References: Subject: Re: Question on shooting a line Date: Sun, 30 Oct 2005 09:41:29 -0500 Message-ID: Ed, did you forget to climb the tree and grease the limb so the line would slide over? "Ed" wrote in message news:Xns96FEA2142E556spectrumhogstarbandn@207.106.93.175... > > I'm trying to shoot a line over a tree limb to hoist my next > generation of wire dipole. > > I'm using a slingshot, a 1 oz round lead fishing weight, and in this > case, 40# test fishing line. > > Although I have had fair success in the past, I'm having difficulties > lately. My weight won't pull the line down the other side of the limb > beyond where it stopped. > > My Question: What weight do you guys recommend? Does anyone know > what weight is used on the EZhang system? Comments sollicited. > > Right now I'm waiting for the wind to blow and hopefully move the tree > limb enough to make the hanging weight pull my live over to the point > where I can reach it. > > > Ed K7AAT Article: 218904 of rec.radio.amateur.antenna From: "Caveat Lector" References: Subject: Re: Backpack Antenna, help please Message-ID: Date: Sun, 30 Oct 2005 08:32:41 -0800 TRY HF PACK WEB SITE http://www.hfpack.com/ -- CL -- I doubt, therefore I might be ! "Steve - www.ukspeedtraps.co.uk" wrote in message news:dk2l95$1ij$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com... > Hi All > > I want to construct a backpack antenna that can be left on my rucksack and > used when walking. > > The plan is to have a FT817 on my waist and the antenna fitted to the > rucksack. I been playing with a mobile antenna today and can not get the > SWR down without trailing a wire. I don't want a wire trailing behind me. > > Any ideas for a 2m antenna that can be left on a rucksack when walking and > used for transmittion. Height is not a major problem but it has to > realistic and robust. > > Thanks > Steve > > -- > The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk > The UK Weather Guide" @ www.ukstorms.com > Article: 218905 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Backpack Antenna, help please References: Message-ID: Date: Sun, 30 Oct 2005 10:28:27 -0600 Hi Steve Many years ago I use to do early morning exercise walks in the mountain range immediately to the west of Sydney's metro area. As soon as I dropped off the western mountain edge all rptr sigs were still audible on my IC2A but they couldnt hear me. I made up a 2M jpole out of 10mm aluminium and tied it to my backpack with rope and/or rubber straps. The thing wobbled a bit but stayed more or less vertical. The backpack was very floppy, a more rigid one would have been better. There was about a 1/2 metre metal extension from the base of the matching section to faciltate the rope binding. The thing was about 1.3 metres max height above my head. I also built a 10W PA running off 12 D cell NiCd's. Worked very well until the constant battery pack flexing shorted something and the hot wiring melted a hole through the backpack pocket it was sitting in! If the extra matching section length is an issue you might find other ways of end/voltage feeding the 1/2 wave. Lots of possibilities here. You could also use a fibreglass rod with 300 ohm ribbon tied to it in a jpole or slim jim form. Handy in a region of low flying trees. Height on LOS frequencies is everything . Getting the antenna above your head will make a huge difference. Everyone thinks you are a extraterrestrial visitor too! Your present mobile antenna will need a counterpoise. (aka groundplane) I suggest you discard the idea of using it unless you can get use to the trailing 1/4 wave wire(s). Maybe it would work by mounting the antenna on an extension so its base is about head height, then wrapping three ground radials down the sides of the backpack. You could make it more permanent by weaving the wire into the backpack itself. Cheers Bob VK2YQA (in W5) Steve - www.ukspeedtraps.co.uk wrote: > Hi All > > I want to construct a backpack antenna that can be left on my rucksack and > used when walking. Article: 218906 of rec.radio.amateur.antenna Subject: Re: Question on shooting a line From: Ed References: <11m9ceqjqnbs59b@corp.supernews.com> Message-ID: Date: Sun, 30 Oct 2005 17:15:46 GMT Thanks Roy. Good discussion on my qeustions. Ed > I've been doing this on Field Day for a long time. > > First off, I use about 6-8 pound test line. It's heavy enough to pull > a nylon cord back over the tree, but light enough so it comes off > smoothly and so I can get plenty of line on a reel. > > Second, I use teardrop-shaped fishing weights (narrow at the line > end), never round or pyramid. The latter types snag too readily if you > have to pull the weight back up. Try dragging the weight across a > weedy back yard if you need an illustration. > > As for the weight itself -- over the years I slowly increased the > weight to as much as 3 ounces, so it would drop freely through fairly > dense pine and fir trees. But I had an increasing amount of trouble > with the weight coming out of the pouch during the shot, leading to > very short shots and even occasionally a cut elastic unless everything > was just right. Dropping back with the weight cured the shooting > problem, along with using a slingshot with wide spaced arms. I've > settled on about 2 oz as the best compromise between trouble-free > shooting and the ability to drop through the tree. > > I never use this method for a home installation unless it's for no > more than a few days -- the twine or even rope cuts into the tree, > making it impossible to get down. This might not be as much of a > problem with hardwood trees as it is for softer and pitchier conifers. > Also, I've had people tell me that very heavy nylon monofilament is > less prone to this -- I haven't tried it. > > Roy Lewallen, W7EL > Article: 218907 of rec.radio.amateur.antenna Subject: Re: Question on shooting a line From: Ed References: Message-ID: Date: Sun, 30 Oct 2005 17:16:58 GMT Thanks, Fred, (and others). I'll try the plastic bucket method of dispensing next time! Ed Article: 218908 of rec.radio.amateur.antenna From: "Charlie" Subject: Anyone using ZX GP-2W 12m/17m vertical??? Date: Sun, 30 Oct 2005 11:46:13 -0600 Message-ID: <11ma1nl9gnjm3c2@news.supernews.com> I am interested to learn from those that have them installed. It is the only 12M/17M vertical I can find anywhere. Made in Germany with no UISA dealers I can locate. It is just what I need but can't even find reviews of it on eHam. Any info very much appreciated... -- Charlie-AD5TH www.ad5th.com Article: 218909 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Backpack Antenna, help please Date: Sun, 30 Oct 2005 10:45:08 -0800 Message-ID: <11ma55ns0dmj7b9@corp.supernews.com> References: A half wave antenna such as the AEA Hot Rod or the MFJ copy of it works well with no ground plane or trailing wire. The models I mentioned are telescoping, so you can collapse them when not walking. Roy Lewallen, W7EL Steve - www.ukspeedtraps.co.uk wrote: > Hi All > > I want to construct a backpack antenna that can be left on my rucksack and > used when walking. > > The plan is to have a FT817 on my waist and the antenna fitted to the > rucksack. I been playing with a mobile antenna today and can not get the SWR > down without trailing a wire. I don't want a wire trailing behind me. > > Any ideas for a 2m antenna that can be left on a rucksack when walking and > used for transmittion. Height is not a major problem but it has to realistic > and robust. > > Thanks > Steve > Article: 218910 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 20:06:08 +0000 (UTC) Message-ID: References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> "Richard Clark" wrote - > Wanna step out into > the parking lot to talk about this? =================================== A typical USA aggresive attitude towards foreigners. ;o) Article: 218911 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR meter for 2.4ghz Message-ID: References: Date: Sun, 30 Oct 2005 20:15:51 GMT On Sat, 29 Oct 2005 23:27:13 -0500, Chris W <1qazse4@cox.net> wrote: >Can someone tell me where I can get an SWR meter that will work in the >2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several websites >that claim to tell you how to build your own, but none of them have >anywhere enough information for someone who doesn't already know what >they are doing. Firstly, to answer your question. "SWR meters" like you buy off the shelf for HF/VHF/UHF are not commonly used at microwave frequencies, and you are talking about low end microwave frequencies. The nearest equivalent would be to get a directional coupler (a four port device with IN, OUT, FORWARD and REFLECTED ports where the FORWARD and REFLECTED ports are a sample of the forward and reflected (RF) waves). You then measure the RF power at the FORWARD and REFLECTED ports using a wattmeter such as a bolometer wattmeter like the HP432A, and calculate the SWR. Used directional couplers are not very expensive, but power meters are and they (or the bolometer heads) are very sensitive to physical damage. Second, so... now that you have measured / calculated SWR, what are you going to do with it. You haven't told us exactly what you are measuring, but SWR is caused by a multi-dimensional problem, and unless you know that a single adjustment will bring SWR into acceptable range, then SWR doesn't give you enough information. It is almost all CB enthusiasts, most hams, and apparently some WiFi enthusiasts that think SWR gives them all the answers. If you are genuinely interested in the technical aspects of transmission lines and antennas, picking a project at 2.4GHz is possibly a most difficult one for learning the principles because instrumentation is so expensive and components are so small physically (good and bad, but mainly bad). Owen -- Article: 218912 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 15:30:59 -0500 Message-ID: <59edd$43652ddf$97d56aa2$18916@ALLTEL.NET> What da ya mean by that, you want me to kick your limey ass... "Reg Edwards" wrote in message news:dk393g$kma$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com... =================================== > > A typical USA aggresive attitude towards foreigners. ;o) > > Article: 218913 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: antenna lengths References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> Message-ID: Date: Sun, 30 Oct 2005 20:50:17 GMT Reg Edwards wrote: > "Richard Clark" wrote - >>Wanna step out into >>the parking lot to talk about this? > > A typical USA aggresive attitude towards foreigners. ;o) That's also a pick up line, Reg. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 218914 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: antenna lengths Message-ID: <0edam1lvufnurh1boc9bsvav40qccuue87@4ax.com> References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> Date: Sun, 30 Oct 2005 21:07:06 GMT On Sun, 30 Oct 2005 20:50:17 GMT, Cecil Moore wrote: >Reg Edwards wrote: >> "Richard Clark" wrote - >>>Wanna step out into >>>the parking lot to talk about this? >> >> A typical USA aggresive attitude towards foreigners. ;o) > >That's also a pick up line, Reg. :-) Cecil, I don't know whether these guys want to step into the parking lot to trade kicks to the groin, or to smooch... but neither is too edifying! Owen -- Article: 218915 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: SWR meter for 2.4ghz Date: Sun, 30 Oct 2005 14:13:53 -0800 Message-ID: <11mahd8l6rp635f@corp.supernews.com> References: Thanks for the vote of confidence, but I don't have a ready answer. Making an HF SWR meter that works well with 50 mW isn't trivial, and making an SWR meter that's accurate at 2.4 GHz isn't easy, either. Homebrewing either one, let alone the combination, requires considerable experience and skill, which Chris indicates he doesn't have, if even crudely accurate results are desired. Suggestions of a directional coupler or slotted line including detector, obtained complete from eBay or other surplus source, sound like the best ideas to me. Impedance information is available from the slotted line, but either will give enough information to allow adjusting for the best match. Another way to adjust the match would be to put a 50 ohm pad -- 6 dB or so should be plenty of attenuation -- between the signal generator and antenna to insure a 50 ohm source impedance. Then the match can be adjusted for maximum field strength as indicated by a field strength meter. That avoids the need for an SWR meter or any calibration or reference. All you need are fairly decent pad and coax, both of which are easy to come by. Roy Lewallen, W7EL Amos Keag wrote: > I believe a "Slotted Line" would be among the better ways to measure SWR > in this frequency range. > > Ask Cecil or Roy, regular contributors to this list, for their advice. > > AK > > Chris W wrote: > >> Can someone tell me where I can get an SWR meter that will work in the >> 2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several >> websites that claim to tell you how to build your own, but none of >> them have anywhere enough information for someone who doesn't already >> know what they are doing. > > Article: 218916 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 14:33:29 -0800 Message-ID: <11maihtikj385c6@corp.supernews.com> References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> Reg Edwards wrote: > > A typical USA aggresive attitude towards foreigners. ;o) > I hope none of the readers of this newsgroup are tempted to consider Reg's attitude or abrasiveness as typical of his countrymen. I recently returned from three weeks in Great Britain, ranging from southern England to the Isle of Skye in Scotland, and to southern and central Wales. Like on my previous three trips there, I was treated very well by some of the nicest people I know and have met. I, my wife, and son were taken in as house guests by two very good friends in different parts of the country. I'm sure that if I'd displayed the sort of attitude toward the British that Reg constantly does toward Americans, I would have had an entirely different experience. But I'd rather concentrate on what good people have in common. And there are a lot of good people in all countries. As well as a few grumps, of course. Roy Lewallen, W7EL Article: 218917 of rec.radio.amateur.antenna From: Jim - NN7K Subject: Re: SWR meter for 2.4ghz References: Message-ID: Date: Sun, 30 Oct 2005 22:33:09 GMT Might look for items under "Farinon" - they made a 2 gig rig, (PT-2000)? for telephone service , used 3cx100a5's and the rigs were junk - but the ONE thing they had was a SWR/POWER meter , on a panel - and many of those were salvaged to use with replacement equipment. But, much of THAT is being retired, because of Cell sites and other users are buying this equipment for access to those freqs (replaceing with 6 GHz). Also, think Bird's meters are rated to 3 GHz (I have a slug for 1 watt at 2000-2500 GHz), and thusly, also would work with Dielectric, and their predicessor, Coaxial Dynamics meters all of which are based on the BIRD 43 meters, physically, and electric- ally. And, also Struthers 503 Military #'s TS-3686, A.K.A., URM-203 All (except for looks of the meter, are identical to the Bird 43and use the same slugs as Bird manufactures (30 microamp movement). Most likely, there are others, but these come to mind immediatly- Jim - NN7K Chris W wrote: > Can someone tell me where I can get an SWR meter that will work in the > 2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several websites > that claim to tell you how to build your own, but none of them have > anywhere enough information for someone who doesn't already know what > they are doing. Article: 218918 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: SWR meter for 2.4ghz References: <11mahd8l6rp635f@corp.supernews.com> Message-ID: Date: Sun, 30 Oct 2005 16:41:43 -0600 Roy Lewallen wrote: > Thanks for the vote of confidence, but I don't have a ready answer. > > Making an HF SWR meter that works well with 50 mW isn't trivial, and > making an SWR meter that's accurate at 2.4 GHz isn't easy, either. > Homebrewing either one, let alone the combination, requires > considerable experience and skill, which Chris indicates he doesn't have, Experience in electronics, especially when it comes to RF, no. However, I do have considerable skill. I can solder pretty good and when it comes to mechanical components, on a bad day I can cut things accurate to +/- .003" on a good day +/- .001" or better. So with detailed instructions and drawings I can build it as long as it isn't so complex that it isn't worth the time. > if even crudely accurate results are desired. Suggestions of a > directional coupler or slotted line including detector, obtained > complete from eBay or other surplus source, sound like the best ideas > to me. Impedance information is available from the slotted line, but > either will give enough information to allow adjusting for the best > match. > > Another way to adjust the match would be to put a 50 ohm pad -- 6 dB > or so should be plenty of attenuation -- between the signal generator > and antenna to insure a 50 ohm source impedance. Then the match can be > adjusted for maximum field strength as indicated by a field strength > meter. That avoids the need for an SWR meter or any calibration or > reference. All you need are fairly decent pad and coax, both of which > are easy to come by. Sounds easy enough if I knew what a 50 ohm pad was. I guess I should open that ARRL Antenna book and start reading from the beginning. -- Chris (waiting for my call sign to show up on the FCC database) W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218919 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: HIGH Q CAPS FOR VLF LOOP ANTENNA? Date: Sun, 30 Oct 2005 16:37:57 -0600 Message-ID: <16584-43654B45-763@storefull-3254.bay.webtv.net> References: TRABEM wrote: "I didn`t price it yet, but I need more technical information!" There`s a better approach than high "Q" capacitors for a VLF loop. It`s been available since the year 1912 and much used soon after its invention. Edwin H. Armstrong, 1890 - 1964 was radio`s most productive inventor. He invented regenerative control in 1912. I think he awakened his sister in the middle of the middle of the night screaming : "Eureka, I`ve found it!" or something to that effect. It wasn`t ubique for Howard Armstrong to discover things. Following controlled regeneration, he discovered the principle of the superhet in 1918, superregeneration in 1922, and the complete system of frequency modulation in 1933. He would battle RCA and Sarnoff for his entire life over control of his discoveries. I recall seeing a photo of the battery portable radio Howard built and gave his bride as a wedding present on an IEEE magazine cover. Ever since 1912 there have been regenerative circuits introducing a fraction of a receiver`s output back into its input to enhance its amplification and sharpen its selectivity. Some of these are called "Q" multipliers. A "Q" multiplier is an oscillator circuit which has its regenerative feedback adjusted just below the point of oscillation. It amplifies the signal many times and shrinks the apparent bandwidth the tuned circuit accepts. I`ve seen them used for reception of WWV at Boulder on 60 kHz and for other low frequencies. This seems easier than using super parts. Use some positive controlled feedback in the loop circuit. Adjust it for convenience. Best regards, Richard Harrison, KB5WZI Article: 218920 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR meter for 2.4ghz Message-ID: References: Date: Sun, 30 Oct 2005 22:45:36 GMT On Sun, 30 Oct 2005 14:21:39 -0800, Richard Clark wrote: >On Sun, 30 Oct 2005 20:15:51 GMT, Owen Duffy wrote: > >>"SWR meters" like you buy off the shelf for HF/VHF/UHF are not >>commonly used at microwave frequencies, and you are talking about low >>end microwave frequencies. > >Hi Owen, > >You are about to make this too difficult. Richard, in the absence of the specific purpose for the meter, I was guided by the request for an "SWR meter" and offered a solution that would do what most modern "SWR meters" will do, measure power in each direction. It was (IMHO) a fairly complete answer to a functional equivalent that has the needed sensitivity, without regard to what features were essential to the unstated task. I agree that for some purposes, a directional coupler with a detector may provide indication of the least reflected power, even if not an absolute measure. (You could probably buy a used coupler, xtal detector, termination and some attenuators for modest $$$ on Ebay, but it won't be as cheap as going and buying a commercial panel array for 2.4GHz if the objective is just to make a high gain antenna.) I think that the discussion demonstrates that an instrument without appropriate knowledge isn't the full answer, not even half ways there. As for the choice of a sandbox for exploration of antennas and transmission line principles, I think that VHF has a lot of merit for hobbyists. Owen -- Article: 218921 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> <11maihtikj385c6@corp.supernews.com> Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 17:53:45 -0500 Message-ID: Roy, I have to second your opinion. The last time the wife and I were in Europe, we were standing in the airport in Frankfurt heading to Italy, we both at the same time said "Let's go back to England". We like to stay at the Bull in Gerrard's Cross and find the people are wonderful. I was readily accepted into the Denham flying club and enjoyed touring England via private plane. The huge chalk carvings south of London can only be appreciated from the air. I picture Reg as an old socialist that time has passed by, and he has since decided to become a professional curmudgeon. He does provide humor from time to time. We must always remember - Everyone has a purpose in life, even if it is only as a bad example -. I think of him every time I see the brother-in-law on "Keeping Up Appearances" on the BBC. "Roy Lewallen" wrote in message news:11maihtikj385c6@corp.supernews.com... > Reg Edwards wrote: > > > > A typical USA aggresive attitude towards foreigners. ;o) > > > > I hope none of the readers of this newsgroup are tempted to consider > Reg's attitude or abrasiveness as typical of his countrymen. I recently > returned from three weeks in Great Britain, ranging from southern > England to the Isle of Skye in Scotland, and to southern and central > Wales. Like on my previous three trips there, I was treated very well by > some of the nicest people I know and have met. I, my wife, and son were > taken in as house guests by two very good friends in different parts of > the country. > > I'm sure that if I'd displayed the sort of attitude toward the British > that Reg constantly does toward Americans, I would have had an entirely > different experience. But I'd rather concentrate on what good people > have in common. And there are a lot of good people in all countries. As > well as a few grumps, of course. > > Roy Lewallen, W7EL Article: 218922 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: SWR meter for 2.4ghz References: Message-ID: Date: Sun, 30 Oct 2005 20:45:29 -0600 Owen Duffy wrote: >On Sat, 29 Oct 2005 23:27:13 -0500, Chris W <1qazse4@cox.net> wrote: > > > >>Can someone tell me where I can get an SWR meter that will work in the >>2.4 to 2.45 ghz range with 50 to 1000 mW? I have found several websites >>that claim to tell you how to build your own, but none of them have >>anywhere enough information for someone who doesn't already know what >>they are doing. >> >> > >Firstly, to answer your question. > >"SWR meters" like you buy off the shelf for HF/VHF/UHF are not >commonly used at microwave frequencies, and you are talking about low >end microwave frequencies. > >The nearest equivalent would be to get a directional coupler (a four >port device with IN, OUT, FORWARD and REFLECTED ports where the >FORWARD and REFLECTED ports are a sample of the forward and reflected >(RF) waves). You then measure the RF power at the FORWARD and >REFLECTED ports using a wattmeter such as a bolometer wattmeter like >the HP432A, and calculate the SWR. Used directional couplers are not >very expensive, but power meters are and they (or the bolometer heads) >are very sensitive to physical damage. > >Second, so... now that you have measured / calculated SWR, what are >you going to do with it. You haven't told us exactly what you are >measuring, but SWR is caused by a multi-dimensional problem, and >unless you know that a single adjustment will bring SWR into >acceptable range, then SWR doesn't give you enough information. > > That's a fair question. I am working on a few different antenna designs, not my own design but other designs I find on the net. Such as a wave guide antenna, collinear array and helix. In most cases part of the design tells you to adjust a certain part till you have the lowest SWR. That is what I plan to do with it. I am changing the designs some, but only in a mechanical sense that I don't believe will have anything but a positive effect on their electrical characteristics. Such as in the wave guide, instead of using cans of some random size, I found a copper pipe with a 3.5" ID that. Also instead of trying to mount a flat flange connector to a round tube (ugly), I have a method of directly attaching a coax cable to the tube with the center conductor being the radiating element. >It is almost all CB enthusiasts, most hams, and apparently some WiFi >enthusiasts that think SWR gives them all the answers. > > I keep reading about keeping the SWR down, but I'm not sure if I thought this, I certainly don't now :) >If you are genuinely interested in the technical aspects of >transmission lines and antennas, picking a project at 2.4GHz is >possibly a most difficult one for learning the principles because >instrumentation is so expensive and components are so small physically >(good and bad, but mainly bad). > > due to physical limitations it is just a lot easier to work with the small stuff, and I do have the resources to make very accurate parts for the antennas. It's not that I can't work with the lower frequencies, larger antennas, it's just more work and takes up more workshop space. I may try a few at 440 though. Anything lower hz than that I will just buy an antenna and pay/con someone to mount it on my roof and be done with it. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218923 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: SWR meter for 2.4ghz Message-ID: References: Date: Mon, 31 Oct 2005 03:14:28 GMT On Sun, 30 Oct 2005 20:45:29 -0600, Chris W <1qazse4@cox.net> wrote: >That's a fair question. I am working on a few different antenna >designs, not my own design but other designs I find on the net. Such as >a wave guide antenna, collinear array and helix. In most cases part of >the design tells you to adjust a certain part till you have the lowest >SWR. That is what I plan to do with it. I am changing the designs >some, but only in a mechanical sense that I don't believe will have >anything but a positive effect on their electrical characteristics. >Such as in the wave guide, instead of using cans of some random size, I >found a copper pipe with a 3.5" ID that. Also instead of trying to >mount a flat flange connector to a round tube (ugly), I have a method of >directly attaching a coax cable to the tube with the center conductor >being the radiating element. Nevertheless, there are good reasons to use a coax connector. How are you weatherproofing this antenna, and what type / length of coax are you using? > >>It is almost all CB enthusiasts, most hams, and apparently some WiFi >>enthusiasts that think SWR gives them all the answers. >> >> > >I keep reading about keeping the SWR down, but I'm not sure if I thought >this, I certainly don't now :) > The statement that measuring that the SWR is say, 3, doesn't tell you what things to do to improve / fix it. What adjustements do you have, are there matching screws near the launch antenna to match it to the waveguide / space or are you going to "dent tune" it? It may be worth looking for designs that incorporate matching screws. If you get that sorted, Richards suggestion of a simple coupler and diode detector should be enough to match it up, but again I suggest that learning how to calibrate a directional coupler at microwave frequencies is jumping in the deep end. His other suggestion of a simple field strength meter (perhaps another identical antenna + detector) is a short cut to the performance you want without considering the SWR as the lead to that outcome. Owen -- Article: 218924 of rec.radio.amateur.antenna From: "David G. Nagel" Subject: Re: Passive battery switch RFID Date: Sun, 30 Oct 2005 21:34:18 -0600 Message-ID: <11mb4663b5c2dd2@corp.supernews.com> References: Use the passive receiver to power a transistor switch to activate the transmitter. You should be able to induce enough power in the unit to switch some kind of transistor switch connecting the battery to the second stage of the unit. You would have to be careful that only the proper signal activates the unit though. Dave WD9BDZ fh03 wrote: > thanks for your input guys. I havent been able to come online due to > power outages caused by hurricane wilma. > > anyway. the reed switch mentioned would work, but the distance is the > issue. I currently have an rfid reader and passive tag, but they too > work only within a few inches. What I need is for the device to be > activated within 5 feet of the receiver and from my understanding a > reed switch cant do that. > > I know electronic toll payment systems seem to conserve battery, and > thats what i need. Bascially I want to have a battery in the unit, but > I dont want the battery to be connected until we're in that range. The > reason passive devices dont work is because even though the antenna can > provide an induced current, without a battery the tag doesnt have enough > power to be able to transmit over say a few inches, let alone five feet. > So we need battery in the transmitter. The user only carries a > transmitter, so it doenst know when it is within range. I have a > microcontroller that will transmit an ID as soon as it is powered up, > but I dont want it to be on at all times, and I dont want a switch. > I'll look into the "Hall Effect" now and see what its about. > > Thanks again guys, keep it coming. > > Article: 218925 of rec.radio.amateur.antenna From: Chris W <1qazse4@cox.net> Subject: Re: SWR meter for 2.4ghz References: Message-ID: Date: Sun, 30 Oct 2005 23:08:37 -0600 Owen Duffy wrote: >On Sun, 30 Oct 2005 20:45:29 -0600, Chris W <1qazse4@cox.net> wrote: > > > > >>That's a fair question. I am working on a few different antenna >>designs, not my own design but other designs I find on the net. Such as >>a wave guide antenna, collinear array and helix. In most cases part of >>the design tells you to adjust a certain part till you have the lowest >>SWR. That is what I plan to do with it. I am changing the designs >>some, but only in a mechanical sense that I don't believe will have >>anything but a positive effect on their electrical characteristics. >>Such as in the wave guide, instead of using cans of some random size, I >>found a copper pipe with a 3.5" ID that. Also instead of trying to >>mount a flat flange connector to a round tube (ugly), I have a method of >>directly attaching a coax cable to the tube with the center conductor >>being the radiating element. >> >> > >Nevertheless, there are good reasons to use a coax connector. > >How are you weatherproofing this antenna, and what type / length of >coax are you using? > > I have a 4' section of LMR 400 with a female N connector on one end. That connects to the pigtail adapter I have for my wifi pc card. It's hard to describe with out a photo but the connection of the cable to the wave guide will be weather tight. So the only way any moisture could get in is through the far end of the copper pipe. If I ever permanently mount this antenna, some plastic glued to the end of the pipe should work fine. > > > >>>It is almost all CB enthusiasts, most hams, and apparently some WiFi >>>enthusiasts that think SWR gives them all the answers. >>> >>> >>> >>> >>I keep reading about keeping the SWR down, but I'm not sure if I thought >>this, I certainly don't now :) >> >> >> > >The statement that measuring that the SWR is say, 3, doesn't tell you >what things to do to improve / fix it. > > I'm not sure what you are trying to say here. >What adjustements do you have, are there matching screws near the >launch antenna to match it to the waveguide / space or are you going >to "dent tune" it? It may be worth looking for designs that >incorporate matching screws. > > In the case of the wave guide I think the length of the radiating element is the main adjustment. Also the distance from the back of the wave guide to the radiating element but I didn't do anything to make that adjustable, I just did the calculation and had my brother drill the hole with his milling machine, it should be with in +/- .001" of where I calculated it. I may decide to make it adjustable in future versions if this one works out good. The problem is it is hard to come by short lengths of 3 1/2" copper pipe, 3" is easier to come by but it is on the small side from the calculations I made. For the collinear array, 2 of the 3 web sites I have found say to move a decoupling element up and down near the feed point to minimize SWR. They all do something a little different on each end of the antenna and I'm not sure if one is right, all are wrong, or it is just different ways of doing the same thing. Here are the 3 sites I have found on that design. http://www.guerrilla.net/reference/antennas/2ghz_collinear_omni/ http://www.rason.org/Projects/collant/collant.htm http://www.repeater-builder.com/antenna/wa6svt.html For the helix in the ARRL Antenna book it says you have to match the impedance of the antenna to the coax and it says to do that you can adjust the spacing of the wire in the first turn to get it closer to the ground plane and use an SWR meter to know when you have it right. I'm reading this from page 19-29 of the 19th edition of the ARRL Antenna book. I think this design mod of the standard helix is from K6ZMW published in the June 1981 issue of QST. -- Chris W Gift Giving Made Easy Get the gifts you want & give the gifts they want One stop wish list for any gift, >from anywhere, for any occasion! http://thewishzone.com Article: 218926 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: antenna lengths Date: Sun, 30 Oct 2005 21:35:37 -0800 Message-ID: <11mbb9ddjk54e14@corp.supernews.com> References: <29v7m11uu2npjlhh1lv0rvtdb6jnvcnb6e@4ax.com> <11maihtikj385c6@corp.supernews.com> Dan Richardson wrote: > On Sun, 30 Oct 2005 17:53:45 -0500, "Fred W4JLE" > wrote: > > >>I think of him every time I see the brother-in-law on "Keeping Up >>Appearances" on the BBC. > > > Don't you feel that's a bit complimentary whats-his-name and a bit > derogatory to the brother-in-law. > > Danny, K6MHE Samuel Clemens (Mark Twain) is one of the characters in one of Harry Turtledove's excellent "alternate history" books. In the story, Clemens is living in San Francisco and has a dog named after the mayor, whom he detests. After a particularly frustrating meeting with the mayor, Clemens returns home and apologizes to the dog -- "When I named you," he says, "I thought I was insulting the mayor. But it turns out that I was insulting you." Roy Lewallen, W7EL Article: 218927 of rec.radio.amateur.antenna From: reality@america.com Subject: Re: SWR meter for 2.4ghz Date: Sun, 30 Oct 2005 21:46:51 -0800 Message-ID: <7nbbm11nn48egc1078ciu9l3cfls6u8g3l@4ax.com> References: On Sun, 30 Oct 2005 23:08:37 -0600, Chris W <1qazse4@cox.net> wrote: >Owen Duffy wrote: > >>On Sun, 30 Oct 2005 20:45:29 -0600, Chris W <1qazse4@cox.net> wrote: >> >> >> >> >>>That's a fair question. I am working on a few different antenna >>>designs, not my own design but other designs I find on the net. Such as >>>a wave guide antenna, collinear array and helix. In most cases part of >>>the design tells you to adjust a certain part till you have the lowest >>>SWR. That is what I plan to do with it. I am changing the designs >>>some, but only in a mechanical sense that I don't believe will have >>>anything but a positive effect on their electrical characteristics. >>>Such as in the wave guide, instead of using cans of some random size, I >>>found a copper pipe with a 3.5" ID that. Also instead of trying to >>>mount a flat flange connector to a round tube (ugly), I have a method of >>>directly attaching a coax cable to the tube with the center conductor >>>being the radiating element. >>> >>> >> >>Nevertheless, there are good reasons to use a coax connector. >> >>How are you weatherproofing this antenna, and what type / length of >>coax are you using? >> >> >I have a 4' section of LMR 400 with a female N connector on one end. >That connects to the pigtail adapter I have for my wifi pc card. It's >hard to describe with out a photo but the connection of the cable to the >wave guide will be weather tight. So the only way any moisture could >get in is through the far end of the copper pipe. If I ever permanently >mount this antenna, some plastic glued to the end of the pipe should >work fine. > > >> >> >> >>>>It is almost all CB enthusiasts, most hams, and apparently some WiFi >>>>enthusiasts that think SWR gives them all the answers. >>>> >>>> >>>> >>>> >>>I keep reading about keeping the SWR down, but I'm not sure if I thought >>>this, I certainly don't now :) >>> >>> >>> >> >>The statement that measuring that the SWR is say, 3, doesn't tell you >>what things to do to improve / fix it. >> >> >I'm not sure what you are trying to say here. > >>What adjustements do you have, are there matching screws near the >>launch antenna to match it to the waveguide / space or are you going >>to "dent tune" it? It may be worth looking for designs that >>incorporate matching screws. >> >> >In the case of the wave guide I think the length of the radiating >element is the main adjustment. Also the distance from the back of the >wave guide to the radiating element but I didn't do anything to make >that adjustable, I just did the calculation and had my brother drill the >hole with his milling machine, it should be with in +/- .001" of where I >calculated it. I may decide to make it adjustable in future versions if >this one works out good. The problem is it is hard to come by short >lengths of 3 1/2" copper pipe, 3" is easier to come by but it is on the >small side from the calculations I made. > >For the collinear array, 2 of the 3 web sites I have found say to move a >decoupling element up and down near the feed point to minimize SWR. >They all do something a little different on each end of the antenna and >I'm not sure if one is right, all are wrong, or it is just different >ways of doing the same thing. Here are the 3 sites I have found on that >design. > >http://www.guerrilla.net/reference/antennas/2ghz_collinear_omni/ >http://www.rason.org/Projects/collant/collant.htm >http://www.repeater-builder.com/antenna/wa6svt.html > > >For the helix in the ARRL Antenna book it says you have to match the >impedance of the antenna to the coax and it says to do that you can >adjust the spacing of the wire in the first turn to get it closer to the >ground plane and use an SWR meter to know when you have it right. I'm >reading this from page 19-29 of the 19th edition of the ARRL Antenna >book. I think this design mod of the standard helix is from K6ZMW >published in the June 1981 issue of QST. Not that it helps you any, but I had to smile when reading your last sentence - I know K6ZMW from work. FYI, his work background is in the RF Design group for a satellite company so he does indeed know a thing or two about antennas. Article: 218929 of rec.radio.amateur.antenna Message-ID: <313030303837383543660A4434@zetnet.co.uk> Date: Mon, 31 Oct 2005 12:12:52 GMT From: Dave Piggin Subject: Re: Question on shooting a line References: <1130633563.967446.51040@g49g2000cwa.googlegroups.com> If you can, manufacture/fabricate a catapult 6" in front of a fishing reel that has a closed faced spool that has 100 Yards of 6Lb monofilament line on the spool. You might be able to get the local kid to sell you his catapult. Fix them to a piece of wood with the reel at the rear of your lenght of wood "upside down" to the catapult. The reel can be fixed on the wood with insulting tape on the reel feet. The catapult needs fixing on the wood, at the end. Make a fixing to steady it up on the wooden bar. The catapult hand grip goes below the wooden bar. If you use a lenght of wood long enough to support a stock piece that you can pull into your shoulder, this will help in making the target alot easier to "hit" and will give support at the rear, the catapult handle giving support at the front, thus enableing your other hand to pull the catapult rubber back. After tying the line to the weight, (use a pear shaped lead) place the weight in the catapult pouch, release the bail pin and the lead weight is shot over the tree limb. After reaching and acheiving the desired target!! remove the lead weight, tie a nylon cord to it and "reel the line back in" Remove line after reeling back in, put assembly away. Tie your dogbone or insulating piece that's on the end of your wire to the cord, pull your nylon cord back and anchor to anything usable. Jobs a good un. ezy pezy Sounds dead long winded, but simple really. Dave -- Amateur Radio Call Sign M1BTI, Located in Manchester England. Locator square IO83TK Chairman Of Trafford Radio Club. Club Call Signs G0TRG & M1BBP Located at Umist, University Of Manchester Institute For Science And Technology Share What You Know, Learn What You Dont. Article: 218930 of rec.radio.amateur.antenna From: N7ZZT - Eric Oyen Subject: Re: SWR meter for 2.4ghz References: Message-ID: Date: Mon, 31 Oct 2005 06:17:34 -0700 Chris W wrote: > Owen Duffy wrote: >>It is almost all CB enthusiasts, most hams, and apparently some WiFi >>enthusiasts that think SWR gives them all the answers. >> >> > > I keep reading about keeping the SWR down, but I'm not sure if I thought > this, I certainly don't now :) SWR isn't the only important thing to consider. SWR BANDWIDTH is probably more important. once you have it established at its lowest point, you then have to measure the 3 DB dropoff points to determine antenna efficiency. the narrower this band, the higher the antenna efficiency (within limits) However, given the nature of WiFi signals (> 500 Mhz wide), this presents some unusual problems to the mix: balancing Antena efficiency without losing performance. That turns out to be complicated (more so considering that you are working in the microwave bands here and very small changes in antenna length/width can have huge impacts on operation). Now, I have a fair amount of knowledge vis a vis antenna design, but I am, by no means, an expert on them (even less for microwave designs). I would suggest that one check out a few of the ARRL books on antenna design. -- DE N7ZZT Eric Oyen Phoenix, Arizona e-mail: n7zzt(at)hotmail(dot)com the difference between intelligence and stupidity is that intelligence has its limits. Article: 218931 of rec.radio.amateur.antenna From: "W5GT" Subject: WTB: 1 Section 25G in DFW area Message-ID: Date: Mon, 31 Oct 2005 10:12:21 -0600 I need one section of 25G in the Dallas/Ft Worth area. Please contact me at w5gt@arrl.net. Thanks Dave - W5GT Article: 218932 of rec.radio.amateur.antenna From: "RST Engineering" Subject: Re: SWR meter for 2.4ghz Date: Mon, 31 Oct 2005 08:33:09 -0800 Message-ID: <11mchqajdo0hj2d@corp.supernews.com> References: <11mahd8l6rp635f@corp.supernews.com> You left out the most expensive part -- a 2.4 Gig signal generator isn't cheap OR easy to come by. Jim Suggestions of a directional > coupler or slotted line including detector, obtained complete from eBay or > other surplus source, sound like the best ideas to me. Impedance > information is available from the slotted line, but either will give > enough information to allow adjusting for the best match. Article: 218933 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: SWR meter for 2.4ghz Date: Mon, 31 Oct 2005 09:32:55 -0800 Message-ID: <11mclac3eu4m9ac@corp.supernews.com> References: <11mahd8l6rp635f@corp.supernews.com> <11mchqajdo0hj2d@corp.supernews.com> RST Engineering wrote: > You left out the most expensive part -- a 2.4 Gig signal generator > isn't cheap OR easy to come by. > > Jim > True, but because the OP was looking for an SWR meter I assumed he had some sort of signal source. If he doesn't, neither an SWR meter nor any other of the suggested methods will be of much use. Roy Lewallen, W7EL Article: 218934 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna gain question Date: Mon, 31 Oct 2005 10:16:07 -0800 Message-ID: References: <11m6ctlaj9568f9@corp.supernews.com> <1130697713.178097.190440@g43g2000cwa.googlegroups.com> <545am11jsm295ddpo588v5nbtj0u4tedo9@4ax.com> <1130716250.857903.226190@g43g2000cwa.googlegroups.com> Richard Clark wrote: > On 30 Oct 2005 15:50:50 -0800, "lu6etj" wrote: > > >>although that is >>not possible for the whole universe (I suppose this allows me to escape >>elegantly of Richard's question... ;> D >> >>73=B4s for all, and thank you very much for your very interesting and >>instructive habitual postings. > > > Hi Miguel, > > Can there be an escape? Ron's question was posed with an impossible > proposition. A collapsing sphere of electromagnetic energy? This has > so many so many fantastic presumptions built in. On all but the smallest of scales, the sky is quite uniform in its luminosity. It can hardly be described as a "collapsing sphere"; not even from the point of view of a geocentric model of the universe. ac6xg Article: 218935 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna gain question Date: Mon, 31 Oct 2005 10:37:15 -0800 Message-ID: References: <11m6ctlaj9568f9@corp.supernews.com> <1130697713.178097.190440@g43g2000cwa.googlegroups.com> <545am11jsm295ddpo588v5nbtj0u4tedo9@4ax.com> <1130716250.857903.226190@g43g2000cwa.googlegroups.com> <3nocm11d7h0ljkon3km9c5eggnu5mvhepl@4ax.com> Richard Clark wrote: > On Mon, 31 Oct 2005 10:16:07 -0800, Jim Kelley > wrote: > > >>On all but the smallest of scales, the sky is quite uniform in its >>luminosity. It can hardly be described as a "collapsing sphere"; not >>even from the point of view of a geocentric model of the universe. > > > Hi Jim, > > Perhaps not, but "quite uniform" is rather in the eye of the beholder. It's quite impossible to behold anywhere near the smallest of scales by eye, Richard. > When I take panagraphic photographs (a broad scale), it is quite > evident that the uniformity is not very uniform. Another variable is > that polarization is not very uniform either (which, photographically > may be saying the same thing). > > The eye is a wonderful device, but not very precise. It's like the internet in that regard, where people, with just the right amounts of terminology and pomposity, can assume the status of expert at just about anything and everything! ;-) ac6xg Article: 218936 of rec.radio.amateur.antenna From: "Steve - www.ukspeedtraps.co.uk" Subject: Re: Backpack Antenna, help please Date: Mon, 31 Oct 2005 20:30:15 +0000 (UTC) Message-ID: References: <11ma55ns0dmj7b9@corp.supernews.com> "Roy Lewallen" wrote in message news:11ma55ns0dmj7b9@corp.supernews.com... >A half wave antenna such as the AEA Hot Rod or the MFJ copy of it works >well with no ground plane or trailing wire. The models I mentioned are >telescoping, so you can collapse them when not walking. > > Roy Lewallen, W7EL > > Steve - www.ukspeedtraps.co.uk wrote: >> Hi All >> >> I want to construct a backpack antenna that can be left on my rucksack >> and used when walking. >> >> The plan is to have a FT817 on my waist and the antenna fitted to the >> rucksack. I been playing with a mobile antenna today and can not get the >> SWR down without trailing a wire. I don't want a wire trailing behind me. >> >> Any ideas for a 2m antenna that can be left on a rucksack when walking >> and used for transmittion. Height is not a major problem but it has to >> realistic and robust. >> >> Thanks >> Steve >> Many thanks for the help, some good usefull stuff. Thanks Steve The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk The UK Weather Guide" @ www.ukstorms.com Article: 218937 of rec.radio.amateur.antenna From: Ron Subject: Re: Antenna gain question References: Message-ID: Date: Mon, 31 Oct 2005 21:57:46 GMT Question (repeated here for convenience): -------------------------------------------------------------------- Assume a receiving antenna is in the center of a sphere and the received signal is coming in equal amounts from all points on the surface of the sphere. Which receiving antenna would capture more power, an omni or a high gain beam? There are no noise and no losses. --------------------------------------------------------------------- First, thanks for all the comments. They have helped me better understand the answer. I am leaning toward the belief that the omni (isotropic) antenna would capture more power and, as odd as it may seem, would have more gain than a high gain beam (or any other directional antenna for that matter). Here is my thinking: This is a very unusual RF field. Usually the field is assumed to be planar with coherent rays - then antennas behave as expected. But this field originates uniformly from all points on the surface of a sphere. It does not spread but converges at the focal point of the sphere. An isotropic antenna placed at the focal point would collect all of the rays whereas a directional antenna at would not. Therefore, in this particular situation, the isotropic would have higher gain and capture more power than any directional antenna. Please correct me if I am wrong. Ron, W4TQT Article: 218938 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Antenna gain question Date: Mon, 31 Oct 2005 22:56:24 -0000 Message-ID: <11md88ojem25ac1@corp.supernews.com> References: >Question (repeated here for convenience): >-------------------------------------------------------------------- >Assume a receiving antenna is in the center of a sphere and the >received signal is coming in equal amounts from all points on the >surface of the sphere. Which receiving antenna would capture more >power, an omni or a high gain beam? There are no noise and no losses. >--------------------------------------------------------------------- > >First, thanks for all the comments. They have helped me better >understand the answer. I am leaning toward the belief that the omni >(isotropic) antenna would capture more power and, as odd as it may >seem, would have more gain than a high gain beam (or any other >directional antenna for that matter). Here is my thinking: > >This is a very unusual RF field. Usually the field is assumed to be >planar with coherent rays - then antennas behave as expected. But this >field originates uniformly from all points on the surface of a sphere. >It does not spread but converges at the focal point of the sphere. > >An isotropic antenna placed at the focal point would collect all of >the rays whereas a directional antenna at would not. > >Therefore, in this particular situation, the isotropic would have >higher gain and capture more power than any directional antenna. > >Please correct me if I am wrong. Well, for one thing, your model assumes something which does not and cannot exist. It assumes the existence of an actual isotropic antenna. Such cannot actually be constructed - there's no way to get a truly omnidirectional radiation pattern without violating Maxwell's equations. I suspect that you'll find the same problem existing, in the reverse direction, if you try to construct the sort of RF field you're talking about. If you try to specify the E-plane and H-plane field components for a uniform, arriving-from-all-points-of-a-sphere field, I believe that you'll find that you can't achieve your goal: there will always be "seams" (abrupt discontinuities or cancellations) in the field components in some directions. -- 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: 218939 of rec.radio.amateur.antenna From: Jim Kelley Subject: Re: Antenna gain question Date: Mon, 31 Oct 2005 15:33:08 -0800 Message-ID: References: Ron wrote: > Question (repeated here for convenience): > -------------------------------------------------------------------- > Assume a receiving antenna is in the center of a sphere and the received > signal is coming in equal amounts from all points on the surface of the > sphere. Which receiving antenna would capture more power, an omni or a > high gain beam? There are no noise and no losses. > --------------------------------------------------------------------- > > First, thanks for all the comments. They have helped me better > understand the answer. I am leaning toward the belief that the omni > (isotropic) antenna would capture more power and, as odd as it may seem, > would have more gain than a high gain beam (or any other directional > antenna for that matter). Here is my thinking: > > This is a very unusual RF field. Usually the field is assumed to be > planar with coherent rays - then antennas behave as expected. But this > field originates uniformly from all points on the surface of a sphere. Uniformly inward, outward, or both? > It does not spread but converges at the focal point of the sphere. By focal point of the sphere do you mean the center of the sphere? How big of a sphere are we talking about, and where is the antenna in relation to the sphere? > An isotropic antenna placed at the focal point would collect all of the > rays whereas a directional antenna at would not. Probably. > Therefore, in this particular situation, the isotropic would have higher > gain and capture more power than any directional antenna. Not according to the accepted use of the term 'gain' in connection with antennas. > Please correct me if I am wrong. > > Ron, W4TQT In the instance you describe, the antenna with gain will pick up less signal than an antenna without gain. The gain antenna will be able to sense signal arriving from only a fraction of the sphere, whereas the isotropic antenna responds to signals arriving from the entire 4-pi sphere. Therefore, the antenna with less gain produces the greater signal level. But this should often be the case when a directional antenna is pointed away from most of the signal. The omni, on the other hand, is 'pointed toward' this particular signal in all directions. Out of curiosity, what kind of signal source are you interested in? ac6xg Article: 218940 of rec.radio.amateur.antenna From: Roger Subject: Re: Question on shooting a line Message-ID: References: <1130633563.967446.51040@g49g2000cwa.googlegroups.com> <313030303837383543660A4434@zetnet.co.uk> Date: Mon, 31 Oct 2005 18:56:38 -0500 On Mon, 31 Oct 2005 12:12:52 GMT, Dave Piggin wrote: >If you can, manufacture/fabricate a catapult 6" in front of a fishing >reel that has a closed faced spool that has 100 Yards of 6Lb >monofilament line on the spool. >You might be able to get the local kid to sell you his catapult. > Why not just use the rod and reel? Admittedly some can throw farther than they can cast. OTOH in the city of Midland it is illegal to use said catapult, bow, or other mechanical means of throwing things. At least they've not outlawed the use of the rod and reel. Myself, I like a good cross bow. OTOH you'd need a lot more than a 100 yards of monofilament.<:-)) Still it's not problem here as I live out in the country. Roger Halstead (K8RI & ARRL life member) (N833R, S# CD-2 Worlds oldest Debonair) www.rogerhalstead.com Article: 218941 of rec.radio.amateur.antenna Subject: Re: Question on shooting a line From: Ed References: <1130633563.967446.51040@g49g2000cwa.googlegroups.com> <313030303837383543660A4434@zetnet.co.uk> Message-ID: Date: Tue, 01 Nov 2005 01:13:09 GMT > Why not just use the rod and reel? Admittedly some can throw farther > than they can cast. I doubt there are very many people who can either throw, or cast a line, at 70 feet, over a particular branch of a rather densely packed conifer tree. I can do it, however, with a slingshot. A bow or crossbow would be even better, I'll admit. Ed Article: 218942 of rec.radio.amateur.antenna From: Ron Subject: Re: Antenna gain question References: Message-ID: Date: Tue, 01 Nov 2005 01:42:52 GMT This was only a mental exercise to help me visualize the concept of gain. No resemblance to a real antenna or RF field was intended. Thinking about it has helped me understand what antenna gain is (assuming my conclusions are correct). And that's all it was supposed to do. I hope it has helped someone else to do the same. Ron Jim Kelley wrote: > > > Ron wrote: > >> Question (repeated here for convenience): >> -------------------------------------------------------------------- >> Assume a receiving antenna is in the center of a sphere and the >> received signal is coming in equal amounts from all points on the >> surface of the sphere. Which receiving antenna would capture more >> power, an omni or a high gain beam? There are no noise and no losses. >> --------------------------------------------------------------------- >> >> First, thanks for all the comments. They have helped me better >> understand the answer. I am leaning toward the belief that the omni >> (isotropic) antenna would capture more power and, as odd as it may >> seem, would have more gain than a high gain beam (or any other >> directional antenna for that matter). Here is my thinking: >> >> This is a very unusual RF field. Usually the field is assumed to be >> planar with coherent rays - then antennas behave as expected. But this >> field originates uniformly from all points on the surface of a sphere. > > > Uniformly inward, outward, or both? > >> It does not spread but converges at the focal point of the sphere. > > > By focal point of the sphere do you mean the center of the sphere? How > big of a sphere are we talking about, and where is the antenna in > relation to the sphere? > >> An isotropic antenna placed at the focal point would collect all of >> the rays whereas a directional antenna at would not. > > > Probably. > >> Therefore, in this particular situation, the isotropic would have >> higher gain and capture more power than any directional antenna. > > > Not according to the accepted use of the term 'gain' in connection with > antennas. > >> Please correct me if I am wrong. >> >> Ron, W4TQT > > > In the instance you describe, the antenna with gain will pick up less > signal than an antenna without gain. The gain antenna will be able to > sense signal arriving from only a fraction of the sphere, whereas the > isotropic antenna responds to signals arriving from the entire 4-pi > sphere. Therefore, the antenna with less gain produces the greater > signal level. But this should often be the case when a directional > antenna is pointed away from most of the signal. The omni, on the other > hand, is 'pointed toward' this particular signal in all directions. > > Out of curiosity, what kind of signal source are you interested in? > > ac6xg > Article: 218943 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna gain question References: Message-ID: <8zA9f.9066$dO2.6799@newssvr29.news.prodigy.net> Date: Tue, 01 Nov 2005 02:39:00 GMT Ron wrote: > Please correct me if I am wrong. If the moon were made out of green cheese, then a cow could jump over it. That is a true statement, by definition. -- 73, Cecil http://www.qsl.net/w5dxp Article: 218944 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Antenna gain question References: <11m6ctlaj9568f9@corp.supernews.com> <1130697713.178097.190440@g43g2000cwa.googlegroups.com> <545am11jsm295ddpo588v5nbtj0u4tedo9@4ax.com> <1130716250.857903.226190@g43g2000cwa.googlegroups.com> <1130780109.071745.6290@g14g2000cwa.googlegroups.com> <1130789249.346785.153520@o13g2000cwo.googlegroups.com> Message-ID: Date: Tue, 01 Nov 2005 02:48:58 GMT Richard Clark wrote: > An orbital electron only radiates when it changes orbital levels to a > LOWER orbit. His question was about a conductive loop RF antenna. RF radiation from an antenna comes from free electrons. Their associated photon energy levels are correlated to the frequency of the excitation energy, not to changes in atomic orbits. -- 73, Cecil http://www.qsl.net/w5dxp