Article: 220854 of rec.radio.amateur.antenna From: Jim Yanik Subject: Re: Need some pointers on building UHF/microwave 50 ohm termination/power splitter Date: 7 Jan 2006 05:07:02 GMT Message-ID: References: <11rtv0e2m530lfd@corp.supernews.com> Chris Jones wrote in news:11rtv0e2m530lfd@corp.supernews.com: > Paul Burridge wrote: > >> Hi all, >> >> I need a couple of accessories to enable me to make some phase >> measurements with my HP network analyzer. I'd thought I could pick >> these up on ebay easily enough, but note the lack of availably with >> surprise and dismay. >> I need to therefore contrive two precision parts: >> >> Firstly, 50 ohm load that's essentially non-reactive up to 1.3Ghz. >> Power handling only need be a few tens of miliwatts. N-type >> connection. >> >> Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type >> connections, again flat up to 1.3Ghz. No switching needed, >> thankfully. >> >> If I can't source these parts elsewhere, how feasible is it to make >> them up and can anyone point me to any designs on the web that might >> fit the bill? >> >> I'm aware that the introduction of any stray reactances into the >> devices will render all subsequent measurements invalid so I need to >> get these parts right. At least 1.3Ghz capability should be >> achievable for a hobbyist with care. >> >> Thanks, >> P. > > You can make a pretty good 50 Ohm termination with a PCB-mounting SMA > connector. Cut off the centre pin of the PCB-end of the connector > leaving 0.5mm or less protruding (careful of your eyes, the pin can go > shooting off pretty fast, it's hard metal), and then solder two 0.1% > 100 Ohm 0603 resistors between the centre pin and the outer (ground) > part of the connector. The resistors should be diametrically > opposite. > > I made one with 1% resistors and got the following: > s11 < -30dB up to 6GHx and > s11 < -47dB up to 500MHz > > It helps to tweak how flat you lie the resistors on the teflon at the > back of the connector, but without a working VNA you just have to > accept what you get. > > If you want a termination with a N connector, then you could use a > really good adapter with the SMA termination I mentioned above, or > work out something similar with a N connector however I have never > tried that since I mostly use SMA anyway. > > I think a very accurate / flat power divider would be fairly hard to > make well unless you can get boards made with microwave substrates. > If you can work out your measurement setup such that the flatness etc > of the divider is not so important, then that would help. > > There's a guy in the UK selling a one input two output type power > divider with N connectors and a 50 Ohm N termination on e-bay at the > moment if that helps you. > > Chris A two-output splitter,IIRC,uses 3 25 ohm resistors in a Y config. Use a double-sided PCB for the ground plane between the three N connectors. -- Jim Yanik jyanik at kua.net Article: 220855 of rec.radio.amateur.antenna From: Russ Subject: Re: Crimp, Clamp or Solder? Message-ID: <39qur1lfeackmo61hfi0tk6q3de8ku7pbh@4ax.com> References: <76fsq1hrdjvdt82p798efnk9iui6jv4vlo@4ax.com> <113sf.16964$wq.9439@bignews7.bellsouth.net> <0bj2r15i9iic4td11aejgpe330g8b07efe@4ax.com> Date: Sat, 07 Jan 2006 07:10:30 GMT On Sat, 07 Jan 2006 00:44:41 +0100, Paul Burridge wrote: >On Tue, 27 Dec 2005 19:00:57 GMT, "kd5sak" >wrote: > > >>Guess that's right, let's see now. Formula ! car wheels just have one big >>lug nut, don't they? >> > >Pit-stop time is critical. You want to race a car that takes 6 guys >all fumbling in over- intimate proximity to change each wheel? NASCAR crews seem to do just fine with on man at each wheel. Each wheel has five lug nuts. R Article: 220856 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Transmission line help References: <1136601460.068728.122510@g49g2000cwa.googlegroups.com> Message-ID: Date: Sat, 07 Jan 2006 14:24:27 GMT address removed wrote: > I am self studying transmission lines and I can't figure out this > problem. Given Z(r), Z_not, and 'd' you are asked to find Tau(d). To my > understanding, Tau(d) is 1+ Z_r(normalized with Z_not) divided by (1 - > Z_r(normalized by Z_not)). For the data I had, I don't get the phase of > Tau(d) correct. I would really appreciate if you could point out where > I am making the mistake or explain it to me the correct way to > calculate Tau(d). Different texts use different subscripts. Is Z(r) the load impedance and Z_not the characteristic impedance? What is 'd'? Are you using a Z-parameter analysis? From "Fields and Waves in Communication Electronics", by Ramo, Whinnery, and Van Duzer, page 28: rho = (ZL-Z0)/(ZL+Z0) = Vref/Vfor tau = 2*ZL/(ZL+Z0) = (Vfor+Vref)/Vfor where rho is the voltage reflection coefficient and tau is the voltage transmission coefficient. ZL is the load impedance and Z0 is the characteristic impedance of the transmission line. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220857 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: MFJ974H References: <1136540435.263601.115880@o13g2000cwo.googlegroups.com> Message-ID: <%GQvf.9894$UF3.3820@newssvr25.news.prodigy.net> Date: Sat, 07 Jan 2006 14:59:07 GMT Peter wrote: > Hi - just wonder if anyone has any comments on the MFJ 974H tuner, > please. I am thinking of getting one to use with a 260' centre fed > antenna and balanced line. It seems the ideal tuner to use having a > direct balanced output and not one via a balun. There was some discussion about moving the balun from the output of an unbalanced tuner to the input. It is generally accepted that action will not improve things very much. The only difference in that action and what MFJ has done is that, in the MFJ-974H, there is some series capacitor impedance opposing the common mode current. That series impedance varies with capacitor settings and is therefore not constant. The Johnson Matchboxes suppressed common mode current through link coupling (no balun required). The MFJ-974H doesn't use link coupling so the common mode current flows right through the tuning caps. And the MFJ-974H does indeed have a balun function on the source side of the network. It appears to be a w2du 1:1 choke balun. So the MFJ-974H is not as good at choking common mode currents as the Johnson Matchbox and not extremely superior to an unbalanced tuner with a w2du 1:1 choke balun on the output. I'm not trying to discourage anyone but the MFJ-974H may not be an extreme improvement over an unbalanced tuner with a w2du 1:1 choke- balun on the output. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220858 of rec.radio.amateur.antenna From: "Thierry" Subject: radar and health ? Date: Sat, 7 Jan 2006 15:47:01 +0000 (UTC) Message-ID: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Hi, I received this message from a colleague but I cannot answer him. I d not know these systems. Could you help me ? My company has installed a Radar Tower for Port survaillence. The tower is about 50 meter height on top of the of a 3 stories building roof and my office building just below the tower on the same level, 20 meter away >from the tower. At the same time, the surrounding is my working area ( Jetty Terminal for ships loading and unloading activities ). I can say that I'll be around that area 12 hours a day for another 20 years. My question: Is it safe to work in that area???? Thanks in advance Thierry http://www.astrosurf.org/lombry -- Posted via Mailgate.ORG Server - http://www.Mailgate.ORG Article: 220859 of rec.radio.amateur.antenna From: Paul Burridge Subject: Re: Need some pointers on building UHF/microwave 50 ohm termination/power splitter Date: Sat, 07 Jan 2006 16:49:52 +0100 Message-ID: <5bovr1l58sbkhobq21rocii504f7hbfavf@4ax.com> References: On Fri, 06 Jan 2006 19:40:27 -0700, Wes Stewart wrote: >http://cgi.ebay.com/HP-909A-50-Ohm-Coaxial-Termination_W0QQitemZ7577035113QQcategoryZ26237QQssPageNameZWDVWQQrdZ1QQcmdZViewItem Thanks, Wes. I'll keep an eye on it. >> >>Secondly, a 50 ohm power splitter (one feed-in; three outputs) N-type >>connections, again flat up to 1.3Ghz. No switching needed, thankfully. > >I must ask, what is the purpose of this? The (thumping great) service manual that came with this VNA gives various levels of tests that can be performed oneself prior sending the thing away for calibration. The power splitter together with a few other basic items enables the analyzer to 'check itself' for fundamental operating fitness. I'm eager to get measurin' stuff, but need to establish some basic, satisfactory level of accuracy first. Being just a hobbyist, I don't require any absolute standard, thankfully!! -- "What is now proved was once only imagin'd" - William Blake Article: 220860 of rec.radio.amateur.antenna Message-ID: <43BFFBFE.7CB0FE7F@sympatico.ca> From: Dave Holford Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Date: Sat, 07 Jan 2006 12:35:58 -0500 Thierry wrote: > Hi, > > I received this message from a colleague but I cannot answer him. I d > not know these systems. > Could you help me ? > > My company has installed a Radar Tower for Port survaillence. The tower > is about 50 meter height on top of the of a 3 stories building roof and > my office building just below the tower on the same level, 20 meter away > from the tower. At the same time, the surrounding is my working area ( > Jetty Terminal for ships loading and unloading activities ). I can say > that I'll be around that area 12 hours a day for another 20 years. > > My question: > > Is it safe to work in that area???? > > Thanks in advance > Thierry > http://www.astrosurf.org/lombry > > -- > Posted via Mailgate.ORG Server - http://www.Mailgate.ORG I have spent most of my working life around various RADARs starting in my late teens at the Royal Radar Research Establishment; which was flooded with RF from numerous operating systems on a large variety of frequencies - throughout much of the establishment a neon bulb would often light just from the RF environment. The last 25years or so before retirement were in a building with numerous installations, including a long range L band ATC primary and secondary installation which provided some entertainment in idle hours as I computed the radiation pattern - with a surprising degree of accuracy - from the noise emanating from my office radio as the beam swept by. Across the hall was a lunchroom with a large health and safety warning sign on the door that a microwave oven was in the room. Looking out the window one was staring down the throat of an operating marine RADAR less than 30 feet away!! To the best of my knowledge no one who worked there has developed any strange illness that even rumour has related to the RADARs. I retired 10 years ago and have no significant illness. Oh yes, and my kids seem to be relatively normal. (Maybe because I wore aluminum underwear?) Dave Article: 220861 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Message-ID: Date: Sat, 07 Jan 2006 11:16:13 -0600 Hi Thierry I dont have the answers on hand. There are however exposure limits set by legislation in various countries. You will often find websites that help you determining what the conditions are at your location. Amateur radio stations for example meed to be concerned about EMR levels when the radiated power gets high. If you cant find anything on your countries radiocomm authorities site have a look at the US's FCC or Australia's ACMA sites. The exposure limits tend to be a fairly universal thing. I would suggest too that to license such a radar structure a EMR study would have to be done as a matter of course. This is a important part of spectrum and safety planning that is certainly the norm in Australia. I would suspect too that being used for ships at short range the output power would not be nowhere near what is used at longer distances. If perchance it is used for longer range as well, then the antenna system would be designed in such a way that most of the radiated power is horizontal and as such only a small component would be aimed down at your office/work location. This is the same logic as placing a cellphone antenna up very high so that nearby EMR is not an issue. My gut feel is that it is safe. You havent of course provided power and antenna pattern figures for the installation. Cheers Bob W5/VK2YQA Thierry wrote: > > My question: > > Is it safe to work in that area???? > Article: 220862 of rec.radio.amateur.antenna From: You Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> Message-ID: Date: Sat, 07 Jan 2006 18:14:01 GMT In article <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org>, "Thierry" wrote: > Hi, > > I received this message from a colleague but I cannot answer him. I d > not know these systems. > Could you help me ? > > My company has installed a Radar Tower for Port survaillence. The tower > is about 50 meter height on top of the of a 3 stories building roof and > my office building just below the tower on the same level, 20 meter away > from the tower. At the same time, the surrounding is my working area ( > Jetty Terminal for ships loading and unloading activities ). I can say > that I'll be around that area 12 hours a day for another 20 years. > > My question: > > Is it safe to work in that area???? > > Thanks in advance > Thierry > http://www.astrosurf.org/lombry Oh yea, you gonnies are going to shrink up, and you winkie is going to fall off......for sure..... you Article: 220863 of rec.radio.amateur.antenna From: "F4DRH" References: <71286$43bc9d37$42a1bfc2$1899@FUSE.NET> Subject: Re: Stupid question on twin feedline (air) Date: Sat, 7 Jan 2006 20:31:20 +0100 Message-ID: <43c01707$0$6666$8fcfb975@news.wanadoo.fr> Hello Jawod, I have buit a twin leed for my center feeder dipole with PCV tubes: http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=57&album=7&pos=2 Tubes are after filled with glue. You can see here the final result (click on the picture to enlarge it): http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=5&album=7&pos=4 Spacing is 5 cm Distance between spacers is 60 cm It has been installed for 3 years. It has resisted to many strong winds. Good luck Regards Jean-Marc F4DRH www.barbaxoops.com "jawod" a écrit dans le message de news: 71286$43bc9d37$42a1bfc2$1899@FUSE.NET... >I will assume that balanced (air) feedline is homebrew. What >recommendations are there for spacing between the twin lines? Number of >spacers per foot? If homebrew, how to keep spacers from migrating...will >small wire "stays" modify feedline characteristics? > > This is all about feedline to simple dipole or inverted V. > > Thanks, > > a new (old) ham > > jawod aka john Article: 220864 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Matching network for end-fed half wave, Q calculations etc.? Date: Sat, 7 Jan 2006 20:59:08 +0000 (UTC) Message-ID: References: <1136517045.065705.123740@g44g2000cwa.googlegroups.com> <11rtggi4j9pusbb@corp.supernews.com> <1136617337.917831.305030@g14g2000cwa.googlegroups.com> MATCHING END-FED 1/2-WAVE ANTENNAS TO THE TRANSMITTER. Instead of depending on hearsay and old-wives tales, there is a logical way of selecting tuned-circuit L and C values. To begin, in the case of impedance matching it is always required to maximise power efficiency. It is the power lost in the tuned circuit which matters. To minimise power lost in the tuned circuit it is necessary to minimise the current circulating in it. (Circulating current is the antenna current times working Q but there's no need to know what Q actually is.) For a given radiated power the voltage across the tuned circuit and antenna when at resonance is fixed. So to minimise circulating current the reactances of L and C should be as high as practicably possible. That's obvious! So for a high reactance of C (which is approximately the reactance of L), C should be mimised. The limit on the smallness of C is the minimum setting value of the tuning capacitor, plus coil self-capacitance, plus stray capacitance associated with wiring and connections to the end of the antenna, plus an allowance for the antenna not being exactly at resonance, plus a small 'safety' margin to allow the tuning capacitor to be adjusted to either above or below resonance. For half-wave antennas at frequencies below 11 MHz a tuning capacitor setting of 20 or 25 pF is suitable. This choice automatically sets the value of the inductance (which is usually higher than the inductance value of a roller inductor and can be home-brewed quite easily.) The maximum setting of the tuning capacitor allows the circuit with the antenna to be tuned to the lower frequency bands. But efficiency will be reduced on lower frequency bands due to smaller reactances of L and C and the greater circulating current. Note that the reactances of L and C are always approximately equal to each other. Theoretically, if the antenna length is slightly shorter than 1/2-wavelength, then it is impossible to obtain an impedance match with this particular circuit. You can't have a tuning capacitor less than zero pF. It is prudent to select the overall antenna length to be a few feet longer than 1/2-wavelength at the desired operating frequency. On the other hand, it is just as well to remember, a non-resonant end-fed antenna wire is no less efficient than an exactly resonant wire provided it can be matched to whatever load resistance is required by the transmitter. (And the load resistance presented to the tansmitter as indicated by a TLI has nothing to do with the so-called, and imaginary, SWR). As Walter Maxwell has peviously pointed out, SWR = Short Wave Radio. But, despite its diagramatic simplicity, a parallel tuned circuit is a not-so-simple, quite complicated arrangement when used as an impedance matching transformer between an end-fed antenna and the transmitter. No maths needed - just arithmetic. Slight change of topic - I am presently imbibing White, Argentinian, Chardonnay Torrentes. I do hope my use of plain English language does not lead to misunderstandings. May I add that I much prefer a decent, intoxicated, political opposition-party leader to a sober, war-mongering Tony Blair. At least a few of you USA citizens must be acquainted with the relatively trivial events taking place in the 'mother' country. In sympathy with what's happening in the US. When will you impeach your so-called president and rid yourselves of your secret Nazi/OGPU CIA police. I'm sure the Constitution does not allow such people to exist. We would be happy to confine both Blair and Bush, here, in the historic Tower of London, chained to the cold stone walls, for an indefinite period, on bread and water, without access to legal representation, as so many other kidnapped prisoners (disappeared people), for years, are being presently detained without sound reason or charge. Have you no conscience? Or have you no idea what a map of the World looks like? To obtain an elementary understanding of a simple tuned circuit as an impedance-matching circuit, download program TUNEHALF from website below. There are other programs available related to the same subject. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... ========================================= Article: 220865 of rec.radio.amateur.antenna From: "Harold E. Johnson" References: <1136517045.065705.123740@g44g2000cwa.googlegroups.com> <11rtggi4j9pusbb@corp.supernews.com> <1136617337.917831.305030@g14g2000cwa.googlegroups.com> Subject: Re: Matching network for end-fed half wave, Q calculations etc.? Message-ID: Date: Sat, 07 Jan 2006 21:42:37 GMT > To obtain an elementary understanding of a simple tuned circuit as an > impedance-matching circuit, download program TUNEHALF from website > below. There are other programs available related to the same > subject. > Intoxicated BS Diatribe snipped Or, use an "L" network. Same number of components, and it will even match impedances that call for negative component values in a parallel tuned circuit. W4ZCB Article: 220866 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Matching network for end-fed half wave, Q calculations etc.? Date: Sat, 7 Jan 2006 23:18:47 +0000 (UTC) Message-ID: References: <1136517045.065705.123740@g44g2000cwa.googlegroups.com> <11rtggi4j9pusbb@corp.supernews.com> <1136617337.917831.305030@g14g2000cwa.googlegroups.com> > Or, use an "L" network. Same number of components, and it will even match > impedances that call for negative component values in a parallel tuned > circuit. > > W4ZCB ====================================== Actually, with an exact 1/2-wave antenna, an L-network suffers from the same disability as does the simple L and C tuned circuit. This is why automatic antenna tuner manufacturers, which use L-networks, state in their operating handbooks that exactly 1/2-wave antennas should be avoided. But it is not an important matter. Very few antennas are EXACTLY 1/2-wavelength in length. And it is a simple matter to shift the resonant frequency up or down a few KHz. ---- Reg, G4FGQ. Article: 220867 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Dipoles and the rig's RF ground... References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Sun, 08 Jan 2006 00:52:35 GMT Charles Schuler wrote: > Ran a Windom in Texas in 1965 (WA5KBO) with only 150W and burned a hole in > my lip (no joke) with the RF on the metal ring around the microphone! The > Windom was a good performer, but I could not effectively ground the rig. I > was in student housing (College Station) and was not allowed antennas but > improvised! Dang Charles, I did exactly the same thing in 1957. If you had asked me, I would have told you to watch out for those metal microphones when using a Windom. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220868 of rec.radio.amateur.antenna From: Paul Burridge Subject: Re: RF power splitter design (was something else) Date: Sun, 08 Jan 2006 01:07:20 +0100 Message-ID: References: <5bovr1l58sbkhobq21rocii504f7hbfavf@4ax.com> On Sat, 07 Jan 2006 10:25:18 -0700, Wes Stewart wrote: >Okay, I couldn't figure out what operational use it would have. Actually, I've noticed that on checking up the mini circuits pointers that the splitters they manufacture are only good for a given frequency range. And I don't mean DC- Fx; I mean from say 30Mhz - 1000Mhz or similar. I'd have thought this type of stuff would have a bottom end of *DC* not some relatively high radio frequency. We're only talking about power splitters after all, not broadband filters. So why the low frequency cut-off? Are there some capacitantances utilized in these designs and if so, what are they doing there? -- "What is now proved was once only imagin'd" - William Blake Article: 220869 of rec.radio.amateur.antenna From: John_H Subject: Re: RF power splitter design (was something else) References: <5bovr1l58sbkhobq21rocii504f7hbfavf@4ax.com> Message-ID: Date: Sun, 08 Jan 2006 02:15:16 GMT Paul Burridge wrote: > On Sat, 07 Jan 2006 10:25:18 -0700, Wes Stewart > wrote: > > > >>Okay, I couldn't figure out what operational use it would have. > > > Actually, I've noticed that on checking up the mini circuits pointers > that the splitters they manufacture are only good for a given > frequency range. And I don't mean DC- Fx; I mean from say 30Mhz - > 1000Mhz or similar. I'd have thought this type of stuff would have a > bottom end of *DC* not some relatively high radio frequency. We're > only talking about power splitters after all, not broadband filters. > So why the low frequency cut-off? Are there some capacitantances > utilized in these designs and if so, what are they doing there? If all you need is a resistive power divider, the frequency limits should be generous. If you want efficient power dividers (with little loss in the splitter itself) you use wideband transformers to get the power split. Article: 220870 of rec.radio.amateur.antenna From: "Hal Rosser" References: <71286$43bc9d37$42a1bfc2$1899@FUSE.NET> Subject: Re: Stupid question on twin feedline (air) Message-ID: Date: Sat, 7 Jan 2006 22:02:41 -0500 "jawod" wrote in message news:71286$43bc9d37$42a1bfc2$1899@FUSE.NET... > I will assume that balanced (air) feedline is homebrew. What > recommendations are there for spacing between the twin lines? Number of > spacers per foot? If homebrew, how to keep spacers from > migrating...will small wire "stays" modify feedline characteristics? > I've heard some use well-varnished dowels as well as pvc pipe, and pieces of scrap vinyl siding cut to size and drilled for spacers. and for stays, I've heard epoxy, super-glue, and hot-melt glue works. If the pieces of vinyl (siding scraps) were folded into a "V", then drilled for the wire on each side, the springiness of the vinyl would probably hold itself in place without glue. spacing of spacers would depend on the stiffness of the wire. Use common sense - just need to keep a consistent spacing. It would take more spacers for flexible, stranded wire than for stiff solid wire. 10 guage solid wire is stiffer than 20 guage braided stranded wire. Article: 220871 of rec.radio.amateur.antenna From: "Joe S." Subject: Re: GeoTool antenna mounts for pickup truck stake holes Date: Sat, 7 Jan 2006 22:57:09 -0500 Message-ID: References: "Joe S." wrote in message news:dpk46e01m06@news4.newsguy.com... > Anyone have experience with these mounts? > > http://www.geotool.com/antmount.htm > > As you see from their website, the mounts are mounted into the stake holes > in the sides of a pickup bed. Anyone here used these mounts? What was > your experience? What truck? How difficult/easy was the installation? > Has the mount lasted? > > Thanks. > > Thanks to all who replied. I checked out the GeoTool website, read their instructions, etc. Then, I investigated my truck and it looks like a simple installation -- the interior of the stake hole is readily accessible with the taillight fixture removed. I ordered two of the GeoTool mounts today -- one for a Radiall/Larsen dual-bander VHF/UHF and one for an ASAT-120. Will post photos of the installation later. > Article: 220872 of rec.radio.amateur.antenna From: "Gary Smith" Subject: Dick Smith Radio Direction Finder Date: Sun, 8 Jan 2006 23:56:31 +1100 Message-ID: Hi, i have aquired an old Dick Smith Radio Direction Finder unit but there is no ASU (Antenna Switching Unit) or antennas with it. I would like to know if someone might have information on how to build the antennas and ASU and any more information on the kit itself. Thanks Gary Article: 220873 of rec.radio.amateur.antenna Date: Mon, 09 Jan 2006 00:28:25 +1100 From: Simon Templar Subject: Re: Dick Smith Radio Direction Finder References: Message-ID: <43c11379$1_2@news.melbourne.pipenetworks.com> Gary Smith wrote: > Hi, i have aquired an old Dick Smith Radio Direction Finder unit but there > is no ASU (Antenna Switching Unit) or antennas with it. I would like to know > if someone might have information on how to build the antennas and ASU and > any more information on the kit itself. > > Thanks > > Gary Could you have found any more newsgroups to cross-post to? -- 73 de Simon, VK3XEM. Article: 220874 of rec.radio.amateur.antenna Message-ID: <43C130E2.1050904@nospam.com> From: Fred Bloggs Subject: Re: RF power splitter design (was something else) References: <5bovr1l58sbkhobq21rocii504f7hbfavf@4ax.com> Date: Sun, 08 Jan 2006 15:33:57 GMT > Actually, I've noticed that on checking up the mini circuits pointers > that the splitters they manufacture are only good for a given > frequency range. And I don't mean DC- Fx; I mean from say 30Mhz - > 1000Mhz or similar. I'd have thought this type of stuff would have a > bottom end of *DC* not some relatively high radio frequency. We're > only talking about power splitters after all, not broadband filters. > So why the low frequency cut-off? Are there some capacitantances > utilized in these designs and if so, what are they doing there? These are ferrite transformer hybrid splitters with fractional dB insertion loss beyond the 3dB split and typically 30dB isolation between output ports. If you want a DC splitter then they have those too- but you're not swift enough to see them. They are simply this. What do you think the loss and isolation is now?: View in a fixed-width font such as Courier. . . . . . v . | . .-/ \ -. . | | . [50] [50] . | | . +-[50]-+ . | | . ^ ^ . . . . Article: 220875 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Correction of my error. Date: Sun, 8 Jan 2006 18:01:40 +0000 (UTC) Message-ID: References: <1136517045.065705.123740@g44g2000cwa.googlegroups.com> <11rtggi4j9pusbb@corp.supernews.com> <1136617337.917831.305030@g14g2000cwa.googlegroups.com> > > Or, use an "L" network. Same number of components, and it will even > match > > impedances that call for negative component values in a parallel > tuned > > circuit. > > > > W4ZCB > ====================================== > > Actually, with an exact 1/2-wave antenna, an L-network suffers from > the same disability as does the simple L and C tuned circuit. > > This is why automatic antenna tuner manufacturers, which use > L-networks, state in their operating handbooks that exactly 1/2-wave > antennas should be avoided. > > But it is not an important matter. Very few antennas are EXACTLY > 1/2-wavelength in length. And it is a simple matter to shift the > resonant frequency up or down a few KHz. > ---- > Reg, G4FGQ. ============================================ It was incorrect of me to say that an L-network suffers from the same disability as the parallel L and C tuned circuit. But it does suffer >from disabilities of a different sort. As you say, Harold, the L-network can be tuned to either side of antenna resonance without calling for impossible negative component settings. The input impedance of a 1/2-wave antenna at resonance is a pure resistance of several thousand ohms. But only very slightly on either side of resonance the series resistive component of Zin falls to a much smaller value - and there arises a series reactive component which can also rise to several thousand ohms. Things change very fast versus frequency. The automatic tuner manufacturers recommend avoidance of end-fed 1/2-wave antennas because very high values of switched inductance are needed on the lower frequency HF bands to provide an impedance match to 50 ohms. You will be aware, in automatic tuners, that both L and C are switched. It is uneconomic to provide large microhenry values of switched inductance for use only on antennas which are rarely found, i.e. on end-fed wires which happen to be exactly 1/2-wave resonant. It is also uneconomic to provide a switched range of small value capac itors, say from 0 to 20 pF. Whereas, with an L & C parallel tuned circuit the coil is home-brewed, it has high intrinsic Q, it is fixed in value, and tuning is done by varying only the capacitor. Impedance matching to the transmitter is done by tapping the transmission line up and down the coil turns. It also transpires that the power efficiency of a parallel tuned L & C matching circuit is higher than an L-network which does the same job. That is because the circuit designer has control over choice of L and C values. Whereas, with an L-match, the L and C values are pre-determined by the values of the load and generator impedances over which the circuit designer has no control. There is an additional complication of L-network design. At certain values of load and generator impedances, the location and values of L's and C's in the circuit can suddenly change versus frequency. And there is always a choice between 2 circuits which perform same job. Anyone interested can download program L_TUNER from website below. The antenna input impdances obtained from program TUNEHALF can be inserted in program L_TUNER and the L and C component values compared between one type of tuner and the other. Remember that with the L-tuner both L and C are variable. With the parallel L and C tuned circuit, in general, only C is variable and impedance matching is accomplished by tapping up the coil. ( or by varying the turns on a link-coupling which, by the way, confers other advantages.) ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220876 of rec.radio.amateur.antenna From: "Harold E. Johnson" References: <1136517045.065705.123740@g44g2000cwa.googlegroups.com> <11rtggi4j9pusbb@corp.supernews.com> <1136617337.917831.305030@g14g2000cwa.googlegroups.com> Subject: Re: Correction of my error. Message-ID: <4Zcwf.692079$_o.561067@attbi_s71> Date: Sun, 08 Jan 2006 18:36:48 GMT > Anyone interested can download program L_TUNER from website below. > > The antenna input impdances obtained from program TUNEHALF can be > inserted in program L_TUNER and the L and C component values compared > between one type of tuner and the other. > > Remember that with the L-tuner both L and C are variable. With the > parallel L and C tuned circuit, in general, only C is variable and > impedance matching is accomplished by tapping up the coil. ( or by > varying the turns on a link-coupling which, by the way, confers other > advantages.) > ---- > ........................................................... > Regards from Reg, G4FGQ MUCH better Reg. At one time, my 160 meter half wave was fed with a parallel tuned circuit using a huge roller inductor (5 inch diameter, foot long surplus thing) I used the same motor driven vacuum variable to obtain resonance and the roller "tap" was only to obtain the 50 Ohm match. Was a fine 160 meter antenna, but my 40 meter quad was an eyesore and difficult to maintain, and I had nothing up for 80. Swapping out the inductor for a piece of Airdux and tapping that for 3 values of inductance and selecting those with an old Ledex motor driven rotary switch gave me all 3 bands with an "L" network. Difficult to accomplish with a parallel tuned circuit without appreciable additional complexity, never noticed any difference in performance on 160 meters. We now have two copycat antennas, up for several years. W4GCK and W1TRF, both are as well pleased as I have been. GCK and I have a directional antenna for the higher bands, TRF uses his on all bands. Regards W4ZCB Article: 220877 of rec.radio.amateur.antenna From: Al Klein Subject: Re: Dick Smith Radio Direction Finder Message-ID: References: Date: Sun, 08 Jan 2006 18:03:41 -0500 On Sun, 8 Jan 2006 23:56:31 +1100, "Gary Smith" wrote: There are probably at least a dozen other RDF designs nased on the same idea floating around on the web. A look at any of them, and a schematic of what you have (draw one if necessary), will tell you how to make what you need. The antennas are usually 1/2 wave dipoles at whatever frequency the unit will be used. Copperweld or wire hangers make decent antennas, although I prefer stainless control wire of the type used on model planes. Article: 220878 of rec.radio.amateur.antenna From: "Gary Smith" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 10:32:54 +1100 Message-ID: References: <43c11379$1_2@news.melbourne.pipenetworks.com> Well, i thought if you need information why not get as much as you can in one go? Seems logical to me. And it's not like i'm posting some dribble, bs, flame. I am getting some good replies so far. Gary Article: 220879 of rec.radio.amateur.antenna From: "Gary Smith" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 10:34:40 +1100 Message-ID: References: Dave, if i had a manual with info on how to build one i'd be down the electronics shop getting the bits and building one as we speak :> Gary "Dave" wrote in message news:Aq-dnVewhKvCg1zeRVn-jw@crocker.com... > they never came with antennas that i know of, you had to build them > yourself. the plans for the asu including circuit board and parts list > are in the manual, they are simple things that you should be able to find > at any radio parts store... assuming you can find one of those today. Article: 220880 of rec.radio.amateur.antenna From: "Gary Smith" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 10:44:30 +1100 Message-ID: References: Thanks Al, but i'm not too good at working out stuff like that, if it's all laid out in kit form i'm ok. and i thought that seeing these things are reasonably critical (antenna units) that if i tried another design i may be waisting my time and parts on something that isn't suited. Thanks for your input. Gary "Al Klein" wrote in message news:a863s15jsisveq0ghaag6ec4fcj7csg3ei@4ax.com... > On Sun, 8 Jan 2006 23:56:31 +1100, "Gary Smith" > wrote: > > There are probably at least a dozen other RDF designs nased on the > same idea floating around on the web. A look at any of them, and a > schematic of what you have (draw one if necessary), will tell you how > to make what you need. > > The antennas are usually 1/2 wave dipoles at whatever frequency the > unit will be used. Copperweld or wire hangers make decent antennas, > although I prefer stainless control wire of the type used on model > planes. Article: 220881 of rec.radio.amateur.antenna From: "Gary Smith" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 10:45:22 +1100 Message-ID: References: <43C15BA4.3F39@orcon.net.nz> Glenn that would be great if you could possibly scan the docs and email them, really appreciate that, Thanks. Gary > I've got one - defective - I think I popped the switching diodes by > accidentally transmitting thru it. I know I've got the dox 'somewhere' > - just gotta dig 'em out. > > From memory, the four pin cable from the main unit sends a rotating DC > bias to each of the switching diodes in the box. There's a diode at the > antenna base too, by design. I haven't opened the box yet, but the > diode at the antenna base is ITT BA 282 Cathode (bar) to coax > shield. > > If/when I find the dox, I'll get back to you. Let me know how you > progress. > > Glenn ZL2TLD Article: 220882 of rec.radio.amateur.antenna Subject: Re: Dipoles and the rig's RF ground... From: Dave Oldridge References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Mon, 09 Jan 2006 03:26:39 GMT "Charles Schuler" wrote in news:A_SdnaQv_rICElzeRVn-gQ@comcast.com: > > >> Dang Charles, I did exactly the same thing in 1957. If you had >> asked me, I would have told you to watch out for those metal >> microphones when using a Windom. > > I only made that mistake once! That burn was very slow to heal, by > the way. I clearly understood several principles after that. > Close-talking the mic and over-modulation was the least of them. This is where those artificial ground things come in handy. But the end of the counterpoise needs to be where it can do no harm, as that's where the artificial ground sticks the voltage. -- Dave Oldridge+ ICQ 1800667 Article: 220883 of rec.radio.amateur.antenna Date: Sun, 08 Jan 2006 22:45:40 -0500 From: jawod Subject: Any experience with the G5RV multiband wire antenna? Message-ID: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> The G5RV antenna can be found by googling. Anyone using this arrangement. It uses a coax feed to balanced feed (which variously acts as radiating elements, depending on the band). The author says a balun is not needed but then describes an RF choke that sounds a lot like a balun. I am also concerned about TVI with this system. John Article: 220884 of rec.radio.amateur.antenna From: "DOUGLAS SNOWDEN" Subject: Home Made Hazer Ideas? Message-ID: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Date: Mon, 09 Jan 2006 04:06:22 GMT I have a 60ft Universal Tower (aluminum) that is laying on the ground ready to be tilted up. Before I put it up I would like to build a hazer type system to lift the rotor/antenna up. One VE gave me the idea of using barn door sliders as guides. Trouble is, I can't even find barn door sliders. Seems like it would be a good way to do it. I could build the rotor/antenna mont out of aluminum to make it fairly light. Ideas? Doug N4IJ Harrah, OK Article: 220885 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Mon, 9 Jan 2006 02:19:51 -0500 Message-ID: The choke balun is used because the G5RV is fed with balanced line. They work well, last a long time and require a tuner. I have never had any TVI with one, nor did I ever expect any. "jawod" wrote in message news:184c4$43c1dc66$42a1bfc2$11376@FUSE.NET... > The G5RV antenna can be found by googling. Anyone using this > arrangement. It uses a coax feed to balanced feed (which variously acts > as radiating elements, depending on the band). The author says a balun > is not needed but then describes an RF choke that sounds a lot like a > balun. I am also concerned about TVI with this system. > > John Article: 220886 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> Message-ID: Date: Mon, 09 Jan 2006 05:14:22 GMT jawod wrote: > The G5RV antenna can be found by googling. Anyone using this > arrangement. It uses a coax feed to balanced feed (which variously acts > as radiating elements, depending on the band). The author says a balun > is not needed but then describes an RF choke that sounds a lot like a > balun. I am also concerned about TVI with this system. http://www.cebik.com/wire/g5rv.html http://www.vk1od.net/G5RV/ -- 73, Cecil http://www.qsl.net/w5dxp Article: 220887 of rec.radio.amateur.antenna Message-ID: <43C1F19E.533D@wt.net> Date: Sun, 08 Jan 2006 23:16:14 -0600 From: Mark Keith Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> jawod wrote: > > The G5RV antenna can be found by googling. Anyone using this > arrangement. It uses a coax feed to balanced feed (which variously acts > as radiating elements, depending on the band). The author says a balun > is not needed but then describes an RF choke that sounds a lot like a > balun. I am also concerned about TVI with this system. > > John I'm not crazy about them at all. I'm not a fan of switching feedline types midroute to the antenna. This applies to other antennas as well. The G5RV was designed mainly as a 20 meter antenna. I'm not sure who decided it was the magical platform for a multiband antenna, but someone did... Someone should get a rope I think... :/ You would be much better ditching the coax and choke, and running straight ladder line, if feeding all bands with a tuner. I think coax fed antennas should see a proper match at the feedpoint of the antenna. If I'm going to use coax, I'm going to run coax the whole way. Some run the "carolina" windoms the same way pretty much.. :( I've directly tested simple coax fed dipoles against both of these antennas. It was fairly ugly. The simple dipole thrashed both of them handily. There is a good bit of loss in all that feedline clutter. Some bands worse than others. If you are going to run a tuner and ladder line for all band use, a simple dipole on the lowest band to be used is a fairly decent compromise. No need to add excess feedline clutter. And loss. :( If you use ladder line all the way, and tune carefully using the least inductance, you will have a fairly efficient system on most all the bands. Most tuners include a 4:1, but some prefer a 1:1 balun instead. MK -- http://web.wt.net/~nm5k Article: 220888 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Mon, 9 Jan 2006 06:50:11 +0000 (UTC) Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <43C1F19E.533D@wt.net> To summarise - dump it ! Article: 220889 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Home Made Hazer Ideas? References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Message-ID: Date: Mon, 09 Jan 2006 10:56:42 GMT DOUG, Depending on how you build the 'hazer', you really don't need rails. The thing will slide up the tubes of the tower just fine, won't even bump on the bolts (much). Also sort of depends on just how 'much' antenna is used and how often it goes up/down, since there is some wear on the tower. 'Normal' use shouldn't be any problem though. A friend built one for me. Not aluminum, and aside from building muscles I didn't particularly want, worked fine. 'Doc Article: 220890 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Home Made Hazer Ideas? References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Message-ID: Date: Mon, 09 Jan 2006 14:23:43 GMT DOUGLAS SNOWDEN wrote: > I have a 60ft Universal Tower (aluminum) that is laying > on the ground ready to be tilted up. Before I put it up > I would like to build a hazer type system to lift the > rotor/antenna up. One VE gave me the idea of using barn door sliders as > guides. Trouble is, I can't even find barn door sliders. Seems like it > would be a good way to do it. > I could build the rotor/antenna mont out of aluminum to make it fairly > light. Ideas? > > > Doug N4IJ > Harrah, OK > > Almost any full service lumber yard in Oklahoma should carry barn door hardware. Also, Home Depot and Tractor Supply carry that sort of item. 73, Gene W4SZ Article: 220891 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> Message-ID: <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Mon, 09 Jan 2006 15:50:20 GMT Ricke wrote: > If SETUP right , There the best HF I've ever used. Maybe the only one? :-) The G5RV, with tuner, is a pretty good 80m, 40m, 20m, and 12m antenna. If the series section is varied from 20 feet to 36 feet, it becomes a very good all-HF-band antenna. With the addition of a parallel 1000pf capacitor with the series section at 22 feet, on 75m my "G5RV" has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220892 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> Message-ID: Date: Mon, 09 Jan 2006 15:51:36 GMT nm5k@wt.net wrote: > It should be illegal to add resisters to otherwise > perfectly good antennas. Except Rhombics, of course. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220893 of rec.radio.amateur.antenna From: Eskay Subject: Re: Home Made Hazer Ideas? References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Message-ID: Date: Mon, 09 Jan 2006 19:05:24 GMT On Mon, 09 Jan 2006 14:23:43 GMT, Gene Fuller wrote: > DOUGLAS SNOWDEN wrote: >> I have a 60ft Universal Tower (aluminum) that is laying >> on the ground ready to be tilted up. Before I put it up >> I would like to build a hazer type system to lift the >> rotor/antenna up. One VE gave me the idea of using barn door sliders as >> guides. Trouble is, I can't even find barn door sliders. Seems like it >> would be a good way to do it. >> I could build the rotor/antenna mont out of aluminum to make it fairly >> light. Ideas? >> >> >> Doug N4IJ >> Harrah, OK >> >> > > Almost any full service lumber yard in Oklahoma should carry barn door > hardware. Also, Home Depot and Tractor Supply carry that sort of item. > > 73, > Gene > W4SZ Maybe he doesn't quite know what to look for. Many years ago an article was published here how to make this Hazer type device..It looked heavy on the side of his tower. If anyone wants the article, I could try to find it and make a scan. Eskay. Article: 220894 of rec.radio.amateur.antenna From: "F4DRH" References: Subject: Re: J-Pole Installation Questions Date: Mon, 9 Jan 2006 21:45:36 +0100 Message-ID: <43c2cb70$0$6663$8fcfb975@news.wanadoo.fr> Hello Paul, You do not need to ground the J-Pole antenna because it is a half-wave dipole feeded with a quarter-wave length. That's why the total antenna lentgh = (1/2 + 1/4) x lambda I have built several 2m J-Pole antennae (with copper pipes) without any problems. The last one was clipped to the TV mast (as yours). The only problem I have experienced was with a dual band (2m/70cm) J-Pole (your case). It was solved by ajusting some of the dimensions. If it is your first J-Pole, I suggest you to built first a mono-band (2m). You will succed because this is the most easier antenna I have ever built!!! Then you will be able to handle a dual band J-Pole. Do not vanish!!!.... This is a very nice antenna. It's main benefit is the very low angle of its radiation over the horizon (between 3 and 4 degrees). I did a contact with Marocco from my location (IN88HR) with 10 watts!!! OK !!! It was a sporadic .... ;-))) Good luck. Contact me if you want more details. Best regards Jean-Marc F4DRH www.barbaxoops.com "> > Antenna: Copper Pipe Dual Band 2M/70CM. Bottom of long leg is tee. lower > leg of tee goes 14" w/ 1/2" copper then transitions to 1" x 36". This is > clamped to two tv mast mounts, anchored to a wooden chimney chase. > > When I built the antenna, it displayed a relatively flat SWR across both > bands, using an MFJ-269. Antenna was free standing in yard, away from > anything to affect it. > > After mounting, the SWR seems to vary from as measured (1:1.2) to off the > map. Thought it was maybe bad coax (LMR-400) but as I checked it, the SWR > came back into line. Someone told me to ground the lower end of the > j-pole, as if it were clamped to a tower. I did this and the SWR goes off > the map. > > Should a J-pole be grounded? if not, how do you protect it or the > structure from a lightning strike? > > Thanks > > Paul P > Article: 220895 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Query.. Date: Mon, 9 Jan 2006 20:55:39 +0000 (UTC) Message-ID: References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> "Cecil Moore" wrote - > Except Rhombics, of course. :-) ==================================== Cecil, get yourself up to date. A terminated rhombic is only 50 percent (or even less) efficient. It transmitts to, and receives from, only half of the available directions. A wicked waste of power. I can't imagine why anybody bothers to use one which is not rotateable. Have you ever erected a 160-meter or 80-meter or even a 40-meter rotateable rhombic? ---- Reg, G4FGQ. Article: 220896 of rec.radio.amateur.antenna From: "F4DRH" References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Mon, 9 Jan 2006 21:55:03 +0100 Message-ID: <43c2cda6$0$19688$8fcfb975@news.wanadoo.fr> Hi John, The "Center Feeded Dipole" (feeding with twin-leads) would give you better performances and no TVI. But if you prefer the G5RV do not use any balun (with magnetic stuff). In somme cases, baluns brings losses (if high SWR on the line). You may find many people that will say that their G5RV works perfectly well with a balun .... they are lucky !!! It is better to connect the coax directly to your antenna tuner. Good luck Jean-Marc F4DRH www.barbaxoops.com "jawod" a écrit dans le message de news: 184c4$43c1dc66$42a1bfc2$11376@FUSE.NET... > The G5RV antenna can be found by googling. Anyone using this arrangement. > It uses a coax feed to balanced feed (which variously acts as radiating > elements, depending on the band). The author says a balun is not needed > but then describes an RF choke that sounds a lot like a balun. I am also > concerned about TVI with this system. > > John Article: 220897 of rec.radio.amateur.antenna From: Wes Stewart Subject: Re: Query.. Date: Mon, 09 Jan 2006 14:05:39 -0700 Message-ID: <0mj5s1drlbpogbeppah6uocoirehpte0pi@4ax.com> References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> On Mon, 9 Jan 2006 20:55:39 +0000 (UTC), "Reg Edwards" wrote: > >"Cecil Moore" wrote - >> Except Rhombics, of course. :-) >==================================== > >Cecil, get yourself up to date. > >A terminated rhombic is only 50 percent (or even less) efficient. Actually, that is not true. A big enough rhombic is nearly self-terminating. The energy radiated is not available to the terminating resistor and thus is not -lost-. >It transmitts to, and receives from, only half of the available >directions. A wicked waste of power. I can't imagine why anybody >bothers to use one which is not rotateable. > >Have you ever erected a 160-meter or 80-meter or even a 40-meter >rotateable rhombic? I completed my 2-meter Worked All Continents award by working VK5MC, who was using stacked rhombics (350 feet/leg), partially steerable by a rope and pulley arrangement. Worked for me [g]. Article: 220898 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Query.. Date: Mon, 9 Jan 2006 21:46:09 +0000 (UTC) Message-ID: References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <0mj5s1drlbpogbeppah6uocoirehpte0pi@4ax.com> "Wes Stewart" wrote in message news:0mj5s1drlbpogbeppah6uocoirehpte0pi@4ax.com... > On Mon, 9 Jan 2006 20:55:39 +0000 (UTC), "Reg Edwards" > wrote: > > > > >"Cecil Moore" wrote - > >> Except Rhombics, of course. :-) > >==================================== > > > >Cecil, get yourself up to date. > > > >A terminated rhombic is only 50 percent (or even less) efficient. > > Actually, that is not true. > > A big enough rhombic is nearly self-terminating. The energy radiated > is not available to the terminating resistor and thus is not -lost-. > > >It transmitts to, and receives from, only half of the available > >directions. A wicked waste of power. I can't imagine why anybody > >bothers to use one which is not rotateable. > > > >Have you ever erected a 160-meter or 80-meter or even a 40-meter > >rotateable rhombic? > > I completed my 2-meter Worked All Continents award by working VK5MC, > who was using stacked rhombics (350 feet/leg), partially steerable by > a rope and pulley arrangement. Worked for me [g]. > =========================================== Wes, of course it worked. You would have done even better had it not been terminated. =========================================== Article: 220899 of rec.radio.amateur.antenna Message-ID: <43C2D9BB.9060804@fuse.net> Date: Mon, 09 Jan 2006 16:46:35 -0500 From: jawod Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <43c2cda6$0$19688$8fcfb975@news.wanadoo.fr> F4DRH wrote: > Hi John, > > The "Center Feeded Dipole" (feeding with twin-leads) would give you better > performances and no TVI. > > But if you prefer the G5RV do not use any balun (with magnetic stuff). In > somme cases, baluns brings losses (if high SWR on the line). You may find > many people that will say that their G5RV works perfectly well with a balun > .... they are lucky !!! > It is better to connect the coax directly to your antenna tuner. > > Good luck > > Jean-Marc > F4DRH > www.barbaxoops.com > > > > > > > "jawod" a écrit dans le message de news: > 184c4$43c1dc66$42a1bfc2$11376@FUSE.NET... > >>The G5RV antenna can be found by googling. Anyone using this arrangement. >>It uses a coax feed to balanced feed (which variously acts as radiating >>elements, depending on the band). The author says a balun is not needed >>but then describes an RF choke that sounds a lot like a balun. I am also >>concerned about TVI with this system. >> >>John > > > Thanks to all for advice! It seems likely that, as I re-enter ham radio, I will be using a rig with an SO-239 plug as an output. The unit I am considering has an internal ATU. So, it would appear likely that SOME coax will be used. I've read articles that indicate a simple PVC pipe wound with 20 or so turns of coax is sufficient for a coax to dipole configuration. I guess I am trying to have a multiband dipole antenna that uses the low-loss ladder line as part of the antenna on some bands. This seems consistent with the G5RV. Any thoughts on other designs to accomplish this? Many articles seem to steer clear of series traps in the dipole. I must have TVI as a high potential concern.. Anyway THANKS! Jean-Marc: nice antenna system...your twin lead looks like coax...is it? john Article: 220900 of rec.radio.amateur.antenna From: "F4DRH" References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <43c2cda6$0$19688$8fcfb975@news.wanadoo.fr> <43C2D9BB.9060804@fuse.net> Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Mon, 9 Jan 2006 23:04:39 +0100 Message-ID: <43c2ddf8$0$20163$8fcfb975@news.wanadoo.fr> > > Jean-Marc: nice antenna system...your twin lead looks like coax...is it? > > john Hi John, Here is my twin lead detail: http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=57&album=7&pos=2 ... and the twin lead installed on the center feed (click on picture to enlarge): http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=5&album=7&pos=4 http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=5&album=7&pos=4 The antenna tuner (MacCoy): http://www.barbaxoops.com/modules/xcgal/displayimage.php?pid=46&album=7&pos=0 Good luck Jean-Marc F4DRH www.barbaxoops.com Article: 220901 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Dipoles and the rig's RF ground... Date: Mon, 9 Jan 2006 22:29:58 +0000 (UTC) Message-ID: References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> > Single wire feed. I was a student (living off of my wife) and used what I > could get my hands on. ======================================= A true radio amateur! Just get a random, bent wire into the air. A single-wire feed helps a lot. With a modest ground and a simple tuner you have an efficient, multi-band, go-anywhere antenna system you can be proud of. Anybody who boasts about his G5RV has never tried anything else. ---- Reg. Article: 220902 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Dipoles and the rig's RF ground... Message-ID: <72p5s15hpr0eos67c35nqd9i294ouognju@4ax.com> References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Date: Mon, 09 Jan 2006 22:33:36 GMT On Mon, 9 Jan 2006 22:29:58 +0000 (UTC), "Reg Edwards" wrote: >Anybody who boasts about his G5RV has never tried anything else. Sounds like the text for a bumper sticker! Owen -- Article: 220903 of rec.radio.amateur.antenna From: "Anthony Fremont" References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Subject: Re: Dipoles and the rig's RF ground... Message-ID: Date: Mon, 09 Jan 2006 23:04:05 GMT "Reg Edwards" wrote > > Single wire feed. I was a student (living off of my wife) and used > what I > > could get my hands on. > ======================================= > > A true radio amateur! > > Just get a random, bent wire into the air. A single-wire feed helps a > lot. With a modest ground and a simple tuner you have an efficient, > multi-band, go-anywhere antenna system you can be proud of. > > Anybody who boasts about his G5RV has never tried anything else. Right.....you should hear the bands open up when you launch a kite antenna. There's nothing like a few hundred feet of random long wire up in the air. ;-) WARNING: No one should ever do such a thing for what should be very obvious safety reasons. I'm a big fan of cubical quads, but you need allot of room for them. I'd take one over a yagi any day. I built a two element quad for 10 meters using bamboo fishing poles for the spreaders. The boom was made >from cedar. It lasted about three years before a flying tree limb took it out. I also made an 8 element quad for 2 meters using 1/2" poplar dowel rod spreaders and a wooden boom as well. Man was that thing hard to tune. Weird things happen after the fifth element is added for some reason. Might explain why most have only 4 elements. ;-) Seriously, it really kicked ass but the tornadic storm took it out too. I'll not be making another with that many elements, too fussy but extremely narrow beam w/incredible back side rejection. Article: 220904 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 16:18:57 -0600 Message-ID: References: Gary, I'm in the process of finishing a new display for my "Roanoke Doppler". Do a search on that name and you'll get many hits. For just the antenna, the Homing In Web site has info on both main types in common use. I'm not sure what the Dick Smith does, but perhaps Homing-In talks about it. Homing In is the place to start: http://members.aol.com/homingin/index.html It has antenna system (typically 1/4 wave whips for the Ham units) references: Down a ways on the main page under Home Built: http://members.aol.com/homingin/newdopant2.html This specificlly addresses the Dick Smith unit: http://members.aol.com/homingin/DSEfix.html You can always email K0OV. 73, Steve, K,9.D;C'I "Gary Smith" wrote in message news:dps7ih$cj$1@news-01.bur.connect.com.au... > Dave, if i had a manual with info on how to build one i'd be down the > electronics shop getting the bits and building one as we speak :> > > Gary > > "Dave" wrote in message > news:Aq-dnVewhKvCg1zeRVn-jw@crocker.com... > > they never came with antennas that i know of, you had to build them > > yourself. the plans for the asu including circuit board and parts list > > are in the manual, they are simple things that you should be able to find > > at any radio parts store... assuming you can find one of those today. > > Article: 220905 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Transmission line help Date: Mon, 9 Jan 2006 16:27:20 -0600 Message-ID: References: <1136601460.068728.122510@g49g2000cwa.googlegroups.com> Don't you mean Z_naught (meaning Z0 a.k.a. Z sub zero)? Z_not sounds like an active-low digital signal line. 73, Steve, K9DCI "Cecil Moore" wrote in message news:vaQvf.3981$fb4.1628@newssvr14.news.prodigy.com... > address removed wrote: > > I am self studying transmission lines and I can't figure out this > > problem. Given Z(r), Z_not, and 'd' you are asked to find Tau(d). To my > > understanding, Tau(d) is 1+ Z_r(normalized with Z_not) divided by (1 - > > Z_r(normalized by Z_not)). For the data I had, I don't get the phase of > > Tau(d) correct. I would really appreciate if you could point out where > > I am making the mistake or explain it to me the correct way to > > calculate Tau(d). > > Different texts use different subscripts. Is Z(r) the load > impedance and Z_not the characteristic impedance? What is 'd'? > Are you using a Z-parameter analysis? > > From "Fields and Waves in Communication Electronics", by Ramo, > Whinnery, and Van Duzer, page 28: > > rho = (ZL-Z0)/(ZL+Z0) = Vref/Vfor > > tau = 2*ZL/(ZL+Z0) = (Vfor+Vref)/Vfor > > where rho is the voltage reflection coefficient and tau is the > voltage transmission coefficient. ZL is the load impedance and > Z0 is the characteristic impedance of the transmission line. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 220906 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Still have problems reading MJF-269 Analyzer Date: Mon, 9 Jan 2006 16:34:06 -0600 Message-ID: References: <96ydncE65IOaCCfeRVn-tw@comcast.com> <3rCuf.167640$V7.100747@news-server.bigpond.net.au> David, Be careful of that "Match Efficiency" number read out by the MFJ. I don't remember what they are showing, but I do remember there was a caution in their manual about just what it was and that it was a rather crude indicator. Some over simplified readout. 73, Steve, K,9.D;C'I "David" wrote in message news:3rCuf.167640$V7.100747@news-server.bigpond.net.au... > Amos, > > The circuit is passive (R/L/C) only. I would not expect any non-linearity. > > I suspect the previous post may have been correct. The match was over a > large ratio of impedance (50 Ohms to 4500 Ohms). I expect the small > value of inductor and reasonably low Q was limiting the performance of > the circuit. > > I tried the match again from 50 Ohms to 800 Ohms as a test and found the > MJ-269 showed match efficiency of 90% with SWR dropping to 1.8. These > results are much better. > > Regards > > David > > Amos Keag wrote: > > Have you considered that there may be non-linear effects in the test set > > up? > > > > The MFJ uses several to ten milliwatts in it's circuitry [+10 dBm]. > > Sensitivity is generally measured at the pico-watt [~ -130 dBm] level. > > > > AK > > > > David wrote: > > > >> Hi, > >> > >> I have a matching circuit that matches 50 Ohms to 4500 Ohms in > >> parallel with 2.5pF at 45MHz. > >> > >> The coil was measured at 147nH with a Q of 50 at 45 MHz. > >> > >> The circuit is a C-Tap typology with following values. > >> > >> Tap input to ground = 784pF > >> Tap to hot side of coil = 92pF > >> Par inductor = 147nH > >> > >> My design calculations predict Loaded Q = 26 and BW = 1.7 MHz. > >> > >> I used a 50p trimmer in par with 68pF cap for top of tap to fine tune. > >> > >> A 4k7 resistor and 2p2 cap were placed across the output to simulate > >> the correct load. > >> > >> The test results show BW = 1.7 MHz and Loaded Q = 24.7 (agree with > >> calculated values). > >> > >> When installed on the IF front end, the expected sensitivity is > >> achieved when tuned. This would indicate most of the signal must be > >> getting through or sensitivity would be effected due to mismatch. > >> > >> All seems to look ok but when I attach the MJF-269 Analyzer I get > >> impedance of 280 angle 35 degrees (240 -j 179) for the impedance, I > >> get SWR = 6.1 , return loss of 2.8dB and match efficiency of 48%. > >> > >> I cannot understand why there is such a discrepency between the design > >> values and tested results (using sig gen, spectrum analyzer and power > >> meter) compared to the MJF-269. > >> > >> Is there something I am doing wrong here or is it a mis-interpretation > >> of displayed values ? > >> > >> Thanks for any help. > > > > Article: 220907 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: Dick Smith Radio Direction Finder Date: Mon, 9 Jan 2006 16:24:30 -0600 Message-ID: References: <43C15BA4.3F39@orcon.net.nz> <5JOdnSO7esrq51zeRVn-vA@comcast.com> <43C18707.12BE@orcon.net.nz> "Glenn McAllister" <"(callsign)"@orcon.net.nz> wrote in message news:43C18707.12BE@orcon.net.nz... > ... > The ones in the box switch one of the antennas at a time to the RDF, and > the ones at the base of the antennas groung the out-of-use antennas. > > Glenn ZL2TLD The standard advise from K0OV is to NOT ground the unused antennas, but to leave them open which is in a non resonant state. This is so they have minimal effect on the active antenna and thus do not act like a parasitic element. I'm not sure why, but he recommends having NO amplitude (pattern) effects in your system. 73, Steve, K9DCI. Article: 220908 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Query.. Date: Mon, 09 Jan 2006 15:20:34 -0800 Message-ID: <11s5ru2qve3vje9@corp.supernews.com> References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> Don't get too hung up on efficiency. What counts is signal strength. Suppose you have a bidirectional antenna. Unless you're talking to two people in opposite directions at the same time, it doesn't matter if the antenna is 100% efficient and half the power goes into an unused reverse lobe or whether it goes into a resistor which makes the antenna 50% efficient. The result is exactly the same as far as the other station is concerned. So to the extent that the rhombic isn't optimal, it's because it's inherently bidirectional, not necessarily because it's inefficient. A bidirectional antenna is usually not an optimum choice. For the same number of elements or same amount of real estate, you can usually make a unidirectional antenna which has a single main lobe of about the same width but 3 dB greater gain. Or, you can have a main lobe of about the same gain as before but greater width, which is an advantage when the antenna can't be rotated. However, this doesn't say anything about simplicity, which is the main attractiveness of a rhombic, along with its bandwidth. Roy Lewallen, W7EL Article: 220909 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: radar and health ? Date: Mon, 9 Jan 2006 16:38:38 -0600 Message-ID: References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <1136722082.927929.234700@o13g2000cwo.googlegroups.com> I don't understand being "on the same level" AND being "20 feet below". 73, Steve, K,9.D;C'I I've been working in RF and transmitters for many years and I can say that there are absolutely no side eff eff eff effects. *(:-) "Thierry" wrote in message news:1136722082.927929.234700@o13g2000cwo.googlegroups.com... > OK Thanks Howard and the others. > I have well an article on my website about EMR and health but I hadn't > data about radar. > > Still thanks > Thierry > Article: 220910 of rec.radio.amateur.antenna From: David Subject: Re: Still have problems reading MJF-269 Analyzer References: <96ydncE65IOaCCfeRVn-tw@comcast.com> <3rCuf.167640$V7.100747@news-server.bigpond.net.au> Message-ID: <7uCwf.212503$V7.141570@news-server.bigpond.net.au> Date: Mon, 09 Jan 2006 23:38:43 GMT Steve, The MJK unit is now giving sensible results. I changed the match from 4500 to 800 Ohms. I think the inductor Q at the higher ratio of impedance transform was not high enough. Matching to lower impedance only required a Q of around 8. Steve Nosko wrote: > David, > > Be careful of that "Match Efficiency" number read out by the MFJ. I > don't remember what they are showing, but I do remember there was a caution > in their manual about just what it was and that it was a rather crude > indicator. Some over simplified readout. > > 73, Steve, K,9.D;C'I > > > "David" wrote in message > news:3rCuf.167640$V7.100747@news-server.bigpond.net.au... > >>Amos, >> >>The circuit is passive (R/L/C) only. I would not expect any non-linearity. >> >>I suspect the previous post may have been correct. The match was over a >>large ratio of impedance (50 Ohms to 4500 Ohms). I expect the small >>value of inductor and reasonably low Q was limiting the performance of >>the circuit. >> >>I tried the match again from 50 Ohms to 800 Ohms as a test and found the >>MJ-269 showed match efficiency of 90% with SWR dropping to 1.8. These >>results are much better. >> >>Regards >> >>David >> >>Amos Keag wrote: >> >>>Have you considered that there may be non-linear effects in the test set >>>up? >>> >>>The MFJ uses several to ten milliwatts in it's circuitry [+10 dBm]. >>>Sensitivity is generally measured at the pico-watt [~ -130 dBm] level. >>> >>>AK >>> >>>David wrote: >>> >>> >>>>Hi, >>>> >>>>I have a matching circuit that matches 50 Ohms to 4500 Ohms in >>>>parallel with 2.5pF at 45MHz. >>>> >>>>The coil was measured at 147nH with a Q of 50 at 45 MHz. >>>> >>>>The circuit is a C-Tap typology with following values. >>>> >>>>Tap input to ground = 784pF >>>>Tap to hot side of coil = 92pF >>>>Par inductor = 147nH >>>> >>>>My design calculations predict Loaded Q = 26 and BW = 1.7 MHz. >>>> >>>>I used a 50p trimmer in par with 68pF cap for top of tap to fine tune. >>>> >>>>A 4k7 resistor and 2p2 cap were placed across the output to simulate >>>>the correct load. >>>> >>>>The test results show BW = 1.7 MHz and Loaded Q = 24.7 (agree with >>>>calculated values). >>>> >>>>When installed on the IF front end, the expected sensitivity is >>>>achieved when tuned. This would indicate most of the signal must be >>>>getting through or sensitivity would be effected due to mismatch. >>>> >>>>All seems to look ok but when I attach the MJF-269 Analyzer I get >>>>impedance of 280 angle 35 degrees (240 -j 179) for the impedance, I >>>>get SWR = 6.1 , return loss of 2.8dB and match efficiency of 48%. >>>> >>>>I cannot understand why there is such a discrepency between the design >>>>values and tested results (using sig gen, spectrum analyzer and power >>>>meter) compared to the MJF-269. >>>> >>>>Is there something I am doing wrong here or is it a mis-interpretation >>>>of displayed values ? >>>> >>>>Thanks for any help. >>> >>> > > -- Kind Regards David Huisman General Manager ----------------------------------------------------------------------- ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work (Telemetry, Control, Monitoring, Security, HVAC ...) A.C.N. 107 441 869 Website : http://www.orbitcoms.com PO Box 4474 Lakehaven NSW 2263, AUSTRALIA Phone: 61-2-4393-3627 Fax : 61-2-4393-3685 Mobile: 61-413-715-986 Article: 220911 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> Message-ID: Date: Mon, 09 Jan 2006 23:54:10 GMT Reg Edwards wrote: > A terminated rhombic is only 50 percent (or even less) efficient. But it's 50% in the bad direction, not the good direction. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220912 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1136844730.293136.96470@g14g2000cwa.googlegroups.com> Message-ID: Date: Tue, 10 Jan 2006 00:15:30 GMT nm5k@wt.net wrote: >>The G5RV, with tuner, is a pretty >>good 80m, 40m, 20m, and 12m antenna. > Depends what you compare it to... I bet my paralleled > 80/40/20 dipoles would beat it on all those bands. Not by enough to notice on the other end. The G5RV has a slight amount of gain over your 40m dipole. It has low loss on the ladder-line matching section and an SWR of less than 4:1 on the RG-213 coax. Where are the losses? >>If the series section >>is varied from 20 feet to 36 feet, it becomes a very good >>all-HF-band antenna. With the addition of a parallel 1000pf >>capacitor with the series section at 22 feet, on 75m my "G5RV" >>has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. > > You would be the exception to the rule. And I still really doubt > it's the total equal of a simple coax fed dipole on 80m. It's a 3/8WL dipole on 75m, fed with low-loss ladder-line, a parallel door knob cap, and an SWR of 1.3:1 on the RG-213 coax. Where are the losses? > The "usual" G5RV that most people tend to buy and run > is one of the most pathetic 80m antennas I've ever used > in my life. Well, maybe. The one I bought in 1988 was well designed with a w2du balun and RG-8x coax. It worked well with a tuner and I made lots of improvements as I learned more about it. There was probably something wrong with the particular G5RV's that you have been exposed to. Some people run a 4:1 balun at the coax/twinlead junction on a G5RV. That's the absolute worst thing to do on 75m as the impedance at that point is already low at 16 ohms. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220913 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Dipoles and the rig's RF ground... References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Tue, 10 Jan 2006 00:21:30 GMT Reg Edwards wrote: > Anybody who boasts about his G5RV has never tried anything else. Reg, I replaced my 130 ft. dipole with a G5RV so I could experiment with it. Given my modifications, Nobody can tell it from the 130 ft. dipole so there's no reason to return to the 130 ft. dipole. My G5RV has an SWR of less than 2:1 on all eight HF bands. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220914 of rec.radio.amateur.antenna From: "Bill Booth" <710138@ican.net> References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Mon, 9 Jan 2006 19:50:58 -0500 Message-ID: <7dc71$43c304f3$d169d0f4$29410@PRIMUS.CA> > If SETUP right , There the best HF I've ever used. > I agree ...... the only HF wire antenna I have ever used. You have to pay close attention to the matching at 20m and then it works great. I use 300 ohm ladder line for the feed as I find that works the best. Build one and try it out .......then you can see for yourself. -- Bill Booth VE3NXK Sundridge ON, Canada 79.23.37 W x 45.46.18 N FN05ns Visit my weather WebCam at http://www.almaguin.com/wxcurrent/weather.html Article: 220915 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Query.. Date: Tue, 10 Jan 2006 00:57:10 +0000 (UTC) Message-ID: References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> "Cecil Moore" wrote > Reg Edwards wrote: > > A terminated rhombic is only 50 percent (or even less) efficient. > > But it's 50% in the bad direction, not the good direction. :-) =========================================== In the most simplistic of terms, a rhombic consists of four 1/2-wavelength wires plus a lossy resistor which gets hot. If the four 1/2-wavelength wires are rearranged to form a dipole, plus a reflector, plus two directors, we have only one good direction in which 100% of the power is radiated. Nothing gets hot. Common sense prevails. No need to refer to Eznec. Even a drunken old-wife would know which arrangement to choose, if only because it saves the cost and fitting of a high power, non-reactive resistor. ;o) But no doubt US Army Field Manuals still call upon rhombics. ---- Reg. Article: 220916 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Dipoles and the rig's RF ground... Date: Tue, 10 Jan 2006 01:18:15 +0000 (UTC) Message-ID: References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> "Cecil Moore" wrote My G5RV has an SWR of less than 2:1 > on all eight HF bands. ========================================= The CIA W.M.D. department must have told you that naughty fib. The SWR on your 380-ohm transmission line to the antenna is umpteen times greater than that! Isn't it time you changed the name of your SWR meter? ---- Reg. Article: 220917 of rec.radio.amateur.antenna From: dplatt@radagast.org (Dave Platt) Subject: Re: Query.. Date: Tue, 10 Jan 2006 01:28:03 -0000 Message-ID: <11s63d3hf8jjqe3@corp.supernews.com> References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> In article , Reg Edwards wrote: >In the most simplistic of terms, a rhombic consists of four >1/2-wavelength wires plus a lossy resistor which gets hot. And, in this case, I think the "most simplistic terms" are a misapplication of the way the term is usually used. My recollection is that in practice, rhombics of the sort being referred to have arms which are several wavelengths long. The total double-arm-length of a wire rhombic is often 10 wavelengths or more. In this sort of rhombic, the great majority of the transmitted power is radiated before it reaches the termination resistor. There is little power left to dissipate in the resistor. If the rhombic were unterminated, and the forward-travelling wave were reflected at the end of the rhombic, most of this reflected power would be radiated before it reached the transmitter and were re-reflected. Dissipating the remaining (small) amount of forward wave at the end of the rhombic helps maintain a very high front-to-back ratio. This can be advantageous both when transmitting (no back-spill) and when receiving. I believe that rhombics were popular among U.S. government radio sites for use at coastal sites, for precisely this reason - they were very good at rejecting QRM from landside transmitters, and didn't blast landside receivers with high power. Long, terminated rhombics have another advantage - they maintain a consistent directionality and feedpoint impedance over a wide range of frequencies... rather wider than you can do with a resonant standing-wave antenna such as a reflector/DE/directors beam. >Common sense prevails. No need to refer to Eznec. Even a drunken >old-wife would know which arrangement to choose, if only because it >saves the cost and fitting of a high power, non-reactive resistor. If you're insisting that a "rhombic" may have arms of no longer than 1/2 wavelength, I'd agree. Since that's not the only way to design 'em, though (and is not how some of the better-known ones were designed), I think that your conclusion is overbroad. It's all a matter of serving your needs, whatever they may be. If you're limited on space, and/or want a steerable beam, then a Yagi or similar is probably the best choice. I certainly wouldn't try to put up an effective HF rhombic on my roof! If you've got oodles of space, want to listen (or transmit) only in a single direction, need a lot of front-to-back isolation, and want a broad bandwidth and consistent radiation patterns and a considerable amount of gain, then a long-armed terminated rhombic may be a better choice than the alternatives (e.e. a honking-big LPDA). -- 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: 220918 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Tue, 10 Jan 2006 01:39:44 GMT On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote: >Ricke wrote: >> If SETUP right , There the best HF I've ever used. > >Maybe the only one? :-) The G5RV, with tuner, is a pretty >good 80m, 40m, 20m, and 12m antenna. If the series section >is varied from 20 feet to 36 feet, it becomes a very good >all-HF-band antenna. With the addition of a parallel 1000pf >capacitor with the series section at 22 feet, on 75m my "G5RV" >has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. Now that is one of those things about a G5RV, no two are alike. What are the key factors that "define" a G5RV? The things that I recall from Varney's article were: - 31m long dipole - centre fed - flat top / inverted V - open wire section of half wave length on 20m, from his physical description, Zo about 520 ohms, but IIRC he suggests Zo is not critical - undefined length of either coax of open wire line of undefined, but low Zo (50 - 120 ohms though he seemed to think figure 8 flex has a lower Zo than it probably does). - balun or no balun at the coax to open wire line transition, depending on his article, he changed his mind. My question is how many of these characteristics can be dispensed with, or varied significantly and still legitimately speak of it as a G5RV? I am watching the argument between those who swear by a G5RV and those who swear at a G5RV and suspect that one of the reasons (and not the only reason) is they are not talking about the same thing. There is a tendency to call anything with a ~30m centre fed dipole a G5RV, and yet that component's pattern is independent of everything else (excluding feedline radiation) and its efficiency is quite good independently of everything else. It is "everything" else that contains the losses that result from the dipole's feedpoint load impedance, and it is the "everything else" that makes or breaks the antenna. Owen -- Article: 220919 of rec.radio.amateur.antenna From: "DOUGLAS SNOWDEN" References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Subject: Re: Home Made Hazer Ideas? Message-ID: <35Fwf.5377$%W1.4601@newsread2.news.atl.earthlink.net> Date: Tue, 10 Jan 2006 02:36:47 GMT Thanks for the input, but my tower is tapered and by the time the hazer moved from bottom to top there would be too much slop. That is why I need some sort of rail system. Doug N4IJ "'Doc" wrote in message news:Kjrwf.2251$801.676@newssvr30.news.prodigy.com... > DOUG, > Depending on how you build the 'hazer', you really don't need > rails. The thing will slide up the tubes of the tower just fine, > won't even bump on the bolts (much). Also sort of depends on just > how 'much' antenna is used and how often it goes up/down, since > there is some wear on the tower. 'Normal' use shouldn't be any > problem though. > A friend built one for me. Not aluminum, and aside from building > muscles I didn't particularly want, worked fine. > 'Doc Article: 220920 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Dipoles and the rig's RF ground... References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Tue, 10 Jan 2006 04:57:02 GMT Reg Edwards wrote: > "Cecil Moore" wrote >> My G5RV has an SWR of less than 2:1 >>on all eight HF bands. > > The SWR on your 380-ohm transmission line to the antenna is umpteen > times greater than that! I'm not talking about SWR on the series section transformer, Reg, I'm talking about on the 50 feet of RG-213. And it's not "umpteen times", rather limited to about ten times. > Isn't it time you changed the name of your SWR meter? Nope, for a G5RV with the nominal 70 feet of 50 ohm coax, the SWR meter is indeed reading the SWR on the coax. Remember, I'm not using a tuner. The coax from the G5RV goes directly to the transceiver through the SWR meter. I actually use my SWR meter to display the SWR. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220921 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Message-ID: Date: Tue, 10 Jan 2006 05:13:05 GMT Owen Duffy wrote: > My question is how many of these characteristics can be dispensed > with, or varied significantly and still legitimately speak of it as a > G5RV? Well, with G5RV himself recommending ladder-line all the way to the transmitter (ARRL Antenna Compendium #1) "If this form (of the G5RV) is employed, almost any length (of balanced line) may be used from center of the antenna to the matching network (balanced) output terminals", the paintbrush is pretty broad. I started out with a standard G5RV and modified it on a per band basis to perform on all eight HF bands. 36 ft. of ladder- line works on both 40m and 17m, my two favorite bands. When I switch to 75m, I use 23 ft. of ladder-line with a parallel 1000pf cap. I call that the *PC-50* point, the point at which a (P)arallel (C)apacitor will cause a match to (50) ohms. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220922 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1136844730.293136.96470@g14g2000cwa.googlegroups.com> <1136860946.696895.50410@g44g2000cwa.googlegroups.com> Message-ID: <3xHwf.15613$oW.8393@newssvr11.news.prodigy.com> Date: Tue, 10 Jan 2006 05:23:11 GMT nm5k@wt.net wrote: > W5DXP wrote: >>It has >>low loss on the ladder-line matching section and an SWR >>of less than 4:1 on the RG-213 coax. Where are the losses? > > At the ladderline/choke/coax junction I would suspect. The only thing there that could be lossy would be the choke. Why would a 1000 ohm choke be lossy? >>It's a 3/8WL dipole on 75m, fed with low-loss ladder-line, >>a parallel door knob cap, and an SWR of 1.3:1 on the RG-213 >>coax. Where are the losses? > > Does that version use the choke? Being the data is incomplete, > hard to say at this point. But if there is loss, I can probably > find it.. :/ Yes, but the impedance at that point is very close to 50 ohms and the choke has about 1000 ohms of choking impedance. >>Well, maybe. The one I bought in 1988 was well designed with >>a w2du balun and RG-8x coax. It worked well with a tuner and >>I made lots of improvements as I learned more about it. > > Hummm...Does that mean it's not really a G5RV anymore? Call it a modified G5RV. It still looks like a G5RV. > Whatever I use will never mix > feedline types midroute to the antenna, I know that > for sure. It's like a crapshoot ... Not a crapshoot at all - just an application of a series section. Do you object to 1/4WL of 75 ohm twinlead feeding a full-wave loop? -- 73, Cecil http://www.qsl.net/w5dxp Article: 220923 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Dipoles and the rig's RF ground... Date: Tue, 10 Jan 2006 13:40:19 +0000 (UTC) Message-ID: References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> "Cecil Moore" wrote in message news:y8Hwf.15610$oW.13838@newssvr11.news.prodigy.com... > Reg Edwards wrote: > > "Cecil Moore" wrote > >> My G5RV has an SWR of less than 2:1 > >>on all eight HF bands. > > > > The SWR on your 380-ohm transmission line to the antenna is umpteen > > times greater than that! > > I'm not talking about SWR on the series section transformer, > Reg, I'm talking about on the 50 feet of RG-213. And it's > not "umpteen times", rather limited to about ten times. > > > Isn't it time you changed the name of your SWR meter? > > Nope, for a G5RV with the nominal 70 feet of 50 ohm coax, > the SWR meter is indeed reading the SWR on the coax. > Remember, I'm not using a tuner. The coax from the G5RV > goes directly to the transceiver through the SWR meter. > I actually use my SWR meter to display the SWR. > -- > 73, Cecil http://www.qsl.net/w5dxp ======================================= I see you are happy to change names when in a tight corner. The name "Transmission line" has been conveniently changed to "Series Section Transformer". But it still has standing waves on it far higher than what you claim for all bands. And don't standing waves increase loss on SST's just as much as they do on transmission lines? Louis is turning over in his grave - yet again. But what the heck? A G5RV will work even if you havn't got one. I once set up an 80 feet dipole without a series section transformer. Unsurprisingly - it worked. ;o) ---- Reg. Article: 220924 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <07ednaJgzcDqKF7eRVn-uQ@comcast.com> Message-ID: Date: Tue, 10 Jan 2006 15:25:35 GMT Amos Keag wrote: > A resonant rhombic without a termination resistor is > bidirectional. Yes and, being open-ended, is a *standing-wave* antenna. Contrary to what has been said here on r.r.a.a in the past, Balanis says: "The current and voltage distributions on open-ended antennas are similar to the standing wave patterns on open-ended transmission lines. ... Standing wave antennas, such as the dipole, can be analyzed as traveling wave antennas with waves propagating in opposite directions (forward and backward) and represented by traveling wave currents If and Ib in Figure 10.1(a)." -- 73, Cecil http://www.qsl.net/w5dxp Article: 220925 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Dipoles and the rig's RF ground... References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Tue, 10 Jan 2006 15:48:01 GMT Reg Edwards wrote: > The name "Transmission line" has been conveniently changed to "Series > Section Transformer". > > But it still has standing waves on it far higher than what you claim > for all bands. And don't standing waves increase loss on SST's just as > much as they do on transmission lines? As you know, standing waves increase loss on SST's just as much as they do on transmission lines *OF THE SAME LENGTH*. For instance, on 3.8 MHz, that 300 ohm series section transformer on a G5RV has an SWR of about 20:1 and a line loss of about 0.7 dB, about 12% of one S-unit. That's a small price to pay for multi-band operation. And using Wireman #554 (like I do) instead of 300 ohm twinlead will cut those SST losses down to 0.37 dB, about 6% of an S-unit. > I once set up an 80 feet dipole without a series section transformer. > Unsurprisingly - it worked. ;o) If you fed it with ladder-line, you fed it with a long series section transformer. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220926 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <07ednaJgzcDqKF7eRVn-uQ@comcast.com> Message-ID: <%kRwf.243281$qk4.55259@bgtnsc05-news.ops.worldnet.att.net> Date: Tue, 10 Jan 2006 16:32:59 GMT Cecil Moore wrote: > > Yes and, being open-ended, is a *standing-wave* antenna. > Contrary to what has been said here on r.r.a.a in the > past, Balanis says: "The current and voltage distributions > on open-ended antennas are similar to the standing wave > patterns on open-ended transmission lines. ... Standing > wave antennas, such as the dipole, can be analyzed as > traveling wave antennas with waves propagating in opposite > directions (forward and backward) and represented by > traveling wave currents If and Ib in Figure 10.1(a)." Why would that be of any advantage? Do you believe it is easier to solve for the exact radiated fields by partitioning the standing wave into two components? The real challenge in antenna theory is determining the exact current distribution. Further subdividing or superposing the current is a trivial exercise in comparison, and such manipulation may or may not be useful. In other words, what Balanis says may be true, but so what? 73, Gene W4SZ Article: 220927 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Subject: Re: Dipoles and the rig's RF ground... Date: Tue, 10 Jan 2006 01:02:09 -0500 Message-ID: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> I have both a 130 foot dipole and a G5RV, I can switch between the two and the reports are exactly the same on 75. With 100 watts on the G5RV I have worked well over 100 countries on SSB 75 meters. The day I received the Olivia for my mix w, worked Russia on it with 5 watts on 20 meters. I use it nightly on my Navy Mars nets in the 3 Mhz area. Like the 130 foot dipole I vary the feed line length to tune. Both feedlines are fed from the rig to the ladderline with coax covered with ferrite beads at the junction end. "Cecil Moore" wrote in message news:e6Dwf.18941$UF3.4834@newssvr25.news.prodigy.net... > Reg Edwards wrote: > > Anybody who boasts about his G5RV has never tried anything else. > > Reg, I replaced my 130 ft. dipole with a G5RV so I could > experiment with it. Given my modifications, Nobody can tell > it from the 130 ft. dipole so there's no reason to return > to the 130 ft. dipole. My G5RV has an SWR of less than 2:1 > on all eight HF bands. > -- > 73, Cecil http://www.qsl.net/w5dxp Article: 220928 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Dipoles and the rig's RF ground... Date: Tue, 10 Jan 2006 19:57:54 +0000 (UTC) Message-ID: References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> "Cecil Moore" wrote > If you fed it with ladder-line, you fed it with a long series > section transformer. :-) ========================================= . . . . and your SWR meter is not an SWR meter - it is a transmitter loading indicator. ;o) Go on then - call me a copy cat! ---- Reg. Article: 220929 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <07ednaJgzcDqKF7eRVn-uQ@comcast.com> <%kRwf.243281$qk4.55259@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Tue, 10 Jan 2006 20:15:12 GMT Gene Fuller wrote: > Cecil Moore wrote: >> Yes and, being open-ended, is a *standing-wave* antenna. >> Contrary to what has been said here on r.r.a.a in the >> past, Balanis says: "The current and voltage distributions >> on open-ended antennas are similar to the standing wave >> patterns on open-ended transmission lines. ... Standing >> wave antennas, such as the dipole, can be analyzed as >> traveling wave antennas with waves propagating in opposite >> directions (forward and backward) and represented by >> traveling wave currents If and Ib in Figure 10.1(a)." > > In other words, what Balanis says may be true, but so what? The "so what" is the additional knowledge to be gained by not choosing to ignore the underlying physics. When the forward EM wave hits the end of the dipole, what happens? Essentially the same thing that happens when a forward EM wave hits the end of an open-circuit transmission line. The H-field (current) goes to zero and the E-field (voltage) doubles, i.e. the forward wave existing at that point is completely reflected. That explains why the feedpoint impedance of a 1/2WL dipole is 50-75 ohms instead of the physical characteristic impedance of ~1200 ohms. The feedpoint impedance of a 1/2WL dipole is a virtual impedance caused by destructive interference between the forward and reflected voltages, Vfp = |Vfor|-|Vref|, and constructive interference between the forward and reflected currents, Ifp = |Ifor|+|Iref|, and Zfp = Vfp/Ifp It is interesting to note the consistency of the arguments here on r.r.a.a. Someone says, "'A' is true". Someone else says, "No, 'A' is gobbledygook". After 'A' is proven to be true, the argument shifts to, "OK, so what? Those grapes are probably sour anyway." :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220930 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Recommendation for 915MHz omni antenna Date: Tue, 10 Jan 2006 13:51:04 -0600 Message-ID: <5278-43C41028-632@storefull-3251.bay.webtv.net> References: Howard, W3CQH wrote: "Try a loop yagi." Construction details are given for 1296 MHz Loop Yagis in my 19th edition of the ARRL Antenna book and easily scaled to 915 MHz. Best regards, Richard Harrison, KB5WZI Article: 220931 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <07ednaJgzcDqKF7eRVn-uQ@comcast.com> <%kRwf.243281$qk4.55259@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Tue, 10 Jan 2006 20:23:02 GMT Cecil, I don't understand the "sour grapes" reference. To the contrary, I believe I have argued with you many times that there are multiple ways to solve a problem. Use standing waves or traveling waves as you choose for computational convenience. The only thing that goes into the field-defining equations is the current, not the waves. Your original message implied that may be some special benefit to a *standing-wave* antenna over a *non-standing-wave* antenna. Other than all of the hand-waving, which seems to somehow be connected to your intuitive thinking, there is no physical difference. >> In other words, what Balanis says may be true, but so what? 73, Gene W4SZ Cecil Moore wrote: > Gene Fuller wrote: > >> Cecil Moore wrote: >> >>> Yes and, being open-ended, is a *standing-wave* antenna. >>> Contrary to what has been said here on r.r.a.a in the >>> past, Balanis says: "The current and voltage distributions >>> on open-ended antennas are similar to the standing wave >>> patterns on open-ended transmission lines. ... Standing >>> wave antennas, such as the dipole, can be analyzed as >>> traveling wave antennas with waves propagating in opposite >>> directions (forward and backward) and represented by >>> traveling wave currents If and Ib in Figure 10.1(a)." >> >> >> In other words, what Balanis says may be true, but so what? > > > The "so what" is the additional knowledge to be gained by > not choosing to ignore the underlying physics. When the > forward EM wave hits the end of the dipole, what happens? > Essentially the same thing that happens when a forward EM > wave hits the end of an open-circuit transmission line. > The H-field (current) goes to zero and the E-field (voltage) > doubles, i.e. the forward wave existing at that point is > completely reflected. > > That explains why the feedpoint impedance of a 1/2WL dipole is > 50-75 ohms instead of the physical characteristic impedance > of ~1200 ohms. The feedpoint impedance of a 1/2WL dipole is > a virtual impedance caused by destructive interference > between the forward and reflected voltages, Vfp = |Vfor|-|Vref|, > and constructive interference between the forward and reflected > currents, Ifp = |Ifor|+|Iref|, and Zfp = Vfp/Ifp > > It is interesting to note the consistency of the arguments > here on r.r.a.a. Someone says, "'A' is true". Someone else > says, "No, 'A' is gobbledygook". After 'A' is proven to > be true, the argument shifts to, "OK, so what? Those grapes > are probably sour anyway." :-) Article: 220932 of rec.radio.amateur.antenna From: Me Subject: Re: radar and health ? References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <1136722082.927929.234700@o13g2000cwo.googlegroups.com> Message-ID: Date: Tue, 10 Jan 2006 20:59:42 GMT In article , "Steve Nosko" wrote: > I don't understand being "on the same level" AND being "20 feet below". > > 73, Steve, K,9.D;C'I Seems that you don't understand the Antenna Beamwidths in the Horozontal and Vertical Planes, on Modern Marine Radar Systems. Me Article: 220933 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Tue, 10 Jan 2006 21:14:40 GMT On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote: >Ricke wrote: >> If SETUP right , There the best HF I've ever used. > >Maybe the only one? :-) The G5RV, with tuner, is a pretty >good 80m, 40m, 20m, and 12m antenna. If the series section >is varied from 20 feet to 36 feet, it becomes a very good >all-HF-band antenna. With the addition of a parallel 1000pf >capacitor with the series section at 22 feet, on 75m my "G5RV" >has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ? In that article, on 75m you model a feedpoint impedance of 36-j324, 28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 46.7 deg length of 300 ohm line with 0.007dB loss (optimistic)). At that point, were 50 ohm coax connected directly, the VSWR at the load end of the 50 ohm coax would be 3, however you shunt the 17+j4 with 1000pF to give a new Z of 12.5-j8 that results in a VSWR at the load end of the 50 ohm coax of around 4.1, driving a little more loss into the coax section. Presumably when you say that the capacitor improves the VSWR on 75m, you mean the VSWR on the coax. Did I miss something, how does the capacitor improve the VSWR on 75m? Owen PS I couldn't make the numbers work for 22' as in your quote, where I got a VSWR at the load end of the coax of 27. I couldn't see where the VSWR of 1.3 comes from? -- Article: 220934 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Tue, 10 Jan 2006 21:41:46 GMT On Tue, 10 Jan 2006 21:14:40 GMT, Owen Duffy wrote: >On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote: > >>Ricke wrote: >>> If SETUP right , There the best HF I've ever used. >> >>Maybe the only one? :-) The G5RV, with tuner, is a pretty >>good 80m, 40m, 20m, and 12m antenna. If the series section >>is varied from 20 feet to 36 feet, it becomes a very good >>all-HF-band antenna. With the addition of a parallel 1000pf >>capacitor with the series section at 22 feet, on 75m my "G5RV" >>has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. > >Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ? I have made a mistake during my analysis, let me try again: In that article, on 75m you model a feedpoint impedance of 36-j324, 28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 48.2 deg length of 300 ohm line with 0.007dB loss (optimistic)). At that point, were 50 ohm coax connected directly, the VSWR at the load end of the 50 ohm coax would be 3, however you shunt the 17+j4 with 1000pF to give a new Z of 17.3-j3.0 that results in a VSWR at the load end of the 50 ohm coax of around 2.9, almost identical to the case without the capacitor. Presumably when you say that the capacitor improves the VSWR on 75m, you mean the VSWR on the coax. Did I miss something, how does the capacitor improve the VSWR on 75m? Owen PS I couldn't make the numbers work for 22' as in your quote, where I got a VSWR at the load end of the coax of 27. I couldn't see where the VSWR of 1.3 comes from? -- -- Article: 220935 of rec.radio.amateur.antenna From: "AAA RF Products" Subject: RF Connectors, Adapters & Cable Assemblies Message-ID: Date: Tue, 10 Jan 2006 13:52:37 -0800 For your free copy of our new catalog, please email sales@AAARFProducts.com or see www.aaarfproducts.com or call 949 481 3154 (San Clemente, CA, USA) No minimum order. No handling charges. Article: 220936 of rec.radio.amateur.antenna From: "Fred W4JLE" References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> Subject: Re: Dipoles and the rig's RF ground... Date: Tue, 10 Jan 2006 19:53:11 -0500 Message-ID: <24b83$43c42d12$471d24c1$27562@ALLTEL.NET> Tell me how to coax feed a dipole that works from 3.3 to 4.1 MHz and you have my attention. wrote in message news:1136927708.070996.198280@f14g2000cwb.googlegroups.com... . > But...I am serious about what I say.. If you want the vurry > best 80m dipole, feed it with nuttin but coax. > MK > Article: 220937 of rec.radio.amateur.antenna From: "Jerry" References: <11rr4922agp1acd@corp.supernews.com> Subject: Re: WTB Outbacker Mobile HF Antenna Message-ID: Date: Tue, 10 Jan 2006 16:55:20 -0500 "Reg Edwards" wrote in message news:dpkmb6$87k$1@nwrdmz02.dmz.ncs.ea.ibs-infra.bt.com... > > "Roy Lewallen" wrote - >> Reg Edwards wrote: >> > >> > 9dB is only one and a half S-units. (Ignoring Roy's ancient > S-meter). >> > >> > The Outbacker may still be well worth the money! >> > >> > But that's just the Capitalist System which places Religion above >> > scientific facts. Sorry for becoming a little off topic. >> > >> > A drop of South African Western Cape helps to keep things in >> > proportion. >> >> 9 dB is also the gain of a good long-boom 4 element Yagi over a > dipole. >> You'd have to drink more than a spot of the wine to not see the > difference. >> > ========================================= > > Roy, you have the unfortunate habit of changing the subject in the > middle of a discussion in the forlorn hope of it not being noticed. > > What have 4-element yagis to do with Outbackers? > > By switching to Chinese "Great Wall" white wine I can make my S-meter > read whatever I fancy. You ought to try some! > > But perhaps you are a teetotaller who has never had the pleasure. If > in fact you are indeed a teetotaller, then, I must admit, you deserve > congratulations for having evaded the 'demon' drink. > > It's all in the genes, anyway! I acquired it from my Grandmother. > ---- > Reg. How about someone who simply doesn't LIKE alcoholic drinks? :) I've had a sip of a beer twice in 15 years. Like some that don't like broccoli, I don't like liquor. It all tastes horrible to me and I'd rather have a unspiked Coke! It all tastes the same to me----Nasty! YUCK! BARF! The Coke tastes sweet and, when I drive home afterwards, I know where home IS and can get there unassisted! The only "bad" effect from a Coca Cola is, it makes me have to pee! :) After 57 years, I think I can do without for a few more. Now the broccoli? I love broccoli casserole!! ;) 73 J Article: 220938 of rec.radio.amateur.antenna From: "Jerry" References: <1136481553.458674.149950@g14g2000cwa.googlegroups.com> Subject: Re: friends,please help me!!!!!! Message-ID: Date: Tue, 10 Jan 2006 16:57:04 -0500 wrote in message news:1136481553.458674.149950@g14g2000cwa.googlegroups.com... > Hi Friends, > > I have two dish antennas at the roof of my apartment.They are lying > abandoned > for many years.I want to make use of them.Can i receive any signals > through them ? & If possible how to connect my computer to the dish > receiver & monitor those signals?I dont have any idea about how to get > started.Can any one give me a nice suggestion on how to utilize them ?& > whether any interesting activity can be carried out ? I require a step > by step complete instruction to carry out all the required > activities.Please guide me !!! Simple! Call your Dish Network dealer and he will help you all you need! :) J > Article: 220939 of rec.radio.amateur.antenna From: David Subject: Re: Recommendation for 915MHz omni antenna References: <_RHsf.124838$V7.65294@news-server.bigpond.net.au> Message-ID: Date: Tue, 10 Jan 2006 22:06:31 GMT Howard, How do you get an onmi-directional pattern from this antenna ? The other issue is that at 921MHz, the unit is almost 1m long (too big to mount in our indoor applications) Howard W3CQH wrote: > Try a loop yagi= > > "David" wrote in message > news:_RHsf.124838$V7.65294@news-server.bigpond.net.au... > >>Hi, >> >>I am looking for recommendation for a design of antenna to operate >>in the band 915-928 MHz. >> >>The desired response is omni-directional with gain greater than or equal >>to a 1/2 wave dipole, something that does not require a ground plane >>and is reasonably straight forward to manufacture in-house. >> >>So far I am considering a 1/2 wave vertical dipole with feed through lower >>element, J-Pole and Collinear. >> >>Thanks in advance for any ideas or link to a web site that might have some >>homebrew versions I could replicate and try. >> >> >>-- >> >>Kind Regards >> >>David Huisman > > > -- Kind Regards David Huisman General Manager ----------------------------------------------------------------------- ORBIT COMMUNICATIONS Pty Ltd - Wireless Solutions that Work (Telemetry, Control, Monitoring, Security, HVAC ...) A.C.N. 107 441 869 Website : http://www.orbitcoms.com PO Box 4474 Lakehaven NSW 2263, AUSTRALIA Phone: 61-2-4393-3627 Fax : 61-2-4393-3685 Mobile: 61-413-715-986 Article: 220940 of rec.radio.amateur.antenna From: Pig Bladder Subject: Re: Dipoles and the rig's RF ground... Message-ID: References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Date: Tue, 10 Jan 2006 23:10:37 GMT On Sat, 07 Jan 2006 23:51:47 +0000, Dave wrote: > rf 'ground' is a real misunderstood thing. and things like this point out > just how poorly understood it is. [snip] Broken shift key, huh? -- Flap! The Pig Bladder from Uranus, still waiting for that hot babe to ask what my favorite planet is. ;-j Article: 220941 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Query.. References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <1136670512.505925.207910@g14g2000cwa.googlegroups.com> <07ednaJgzcDqKF7eRVn-uQ@comcast.com> <%kRwf.243281$qk4.55259@bgtnsc05-news.ops.worldnet.att.net> Message-ID: Date: Tue, 10 Jan 2006 23:42:16 GMT Gene Fuller wrote: > I don't understand the "sour grapes" reference. To the contrary, I > believe I have argued with you many times that there are multiple ways > to solve a problem. Actually, you have gone from saying I was wrong to saying that I am right but it doesn't matter. I guess that's an improvement. :-) > Your original message implied that may be some special benefit to a > *standing-wave* antenna over a *non-standing-wave* antenna. Sorry, I never said anything about a standing-wave antenna having some special benefit over a traveling-wave antenna. It was a problem with the inferrence function, not with the implication function. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220942 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1136844730.293136.96470@g14g2000cwa.googlegroups.com> <1136860946.696895.50410@g44g2000cwa.googlegroups.com> <3xHwf.15613$oW.8393@newssvr11.news.prodigy.com> <1136926849.382842.50850@g14g2000cwa.googlegroups.com> Message-ID: Date: Tue, 10 Jan 2006 23:50:50 GMT nm5k@wt.net wrote: > If you change very much with a G5RV, it's not a G5RV > anymore. IE: If you feed a 102 ft dipole with ladder > line, but no choke or coax, it's not a G5RV anymore. But that's exactly what G5RV recommended as one form of his G5RV antenna. > Tell me this...What is the advantage of using the choke, > coax, etc, vs just running straight ladder line the whole > way? The advantage is a pretty good match on 80m, 40m, 20m and 12m that's not guaranteed with straight ladder-line. Some lengths of ladder-line present additional problems. For instance, if one happens upon a current maximum point located at a 4:1 balun, one can take 16 ohms down to 4 ohms. That's going in the wrong direction. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220943 of rec.radio.amateur.antenna Subject: Re: Dipoles and the rig's RF ground... From: Dave Oldridge References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Message-ID: Date: Wed, 11 Jan 2006 00:13:18 GMT "Anthony Fremont" wrote in news:FZBwf.39022$9e.30720 @tornado.texas.rr.com: > > "Reg Edwards" wrote >> > Single wire feed. I was a student (living off of my wife) and used >> what I >> > could get my hands on. >> ======================================= >> >> A true radio amateur! >> >> Just get a random, bent wire into the air. A single-wire feed helps a >> lot. With a modest ground and a simple tuner you have an efficient, >> multi-band, go-anywhere antenna system you can be proud of. >> >> Anybody who boasts about his G5RV has never tried anything else. > > Right.....you should hear the bands open up when you launch a kite > antenna. There's nothing like a few hundred feet of random long wire up > in the air. ;-) > WARNING: No one should ever do such a thing for what should be very > obvious safety reasons. > > I'm a big fan of cubical quads, but you need allot of room for them. I swear OH8OS used to MAKE his own band openings or 15 back in 65 when I used to work him from VE8ML. He had a huge quad, 15 elements, I think, pointed right in my direction. -- Dave Oldridge+ ICQ 1800667 Article: 220944 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 11 Jan 2006 00:13:14 GMT Owen Duffy wrote: > Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ? Nope, that's just an off-the-shelf vanilla G5RV. > In that article, ... Forget that article which only shows why the *standard* G5RV is a fairly well matched antenna on 80m and 40m. > Presumably when you say that the capacitor improves the VSWR on 75m, > you mean the VSWR on the coax. Did I miss something, how does the > capacitor improve the VSWR on 75m? I'm sure you know this already. Given an SWR circle on a Smith Chart that crosses the horizontal resistive line at less than 50 ohms and given the 1/50 conductance circle, those two circles will cross at two points. Where they cross in the capacitive reactance region is the point on the transmission line where a parallel capacitance will bring the impedance at that point to 50+j0 ohms. This is a common matching technique for 75m mobile antennas. The same thing can be done with a coil installed where the circles cross in the inductive reactance region. This technique is described in the ARRL Antenna Book. What I have done on my G5RV is find the point where the SWR circle intersects the 1/50 conductance circle in the capacitive reactance region on 3.8 MHz and install a 1000 pf parallel cap there. My series section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz. Given an SWR circle crossing the 1/50 conductance circle, there's a point where a cap will result in 50 ohms. A little farther, a cap will result in 300 ohms. A little farther, a cap will result in 450 ohms, etc. These are the points just past the current maximum point where one can hang a capacitive stub to achieve a purely resistive impedance. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220945 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Dipoles and the rig's RF ground... References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> Message-ID: Date: Wed, 11 Jan 2006 00:23:21 GMT nm5k@wt.net wrote: > If you want the vurry > best 80m dipole, feed it with nuttin but coax. Well, as a data point, Owen's transmission line loss calculator says there's 0.362 dB loss in 100 ft. of RG-213 feeding a 50 ohm antenna on 75m. The loss using 100 ft. of open-wire feedline feeding a 50 ohm antenna on 75m is 0.169 dB, less than half the loss in the coax. Even the Wireman #554 "450" ohm line is better than the coax at 0.269 dB. Where are the losses in a Ladder- Line fed system? -- 73, Cecil http://www.qsl.net/w5dxp Article: 220946 of rec.radio.amateur.antenna Subject: Re: 8jk From: Dave Oldridge References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> Message-ID: Date: Wed, 11 Jan 2006 00:29:02 GMT "wildboy" wrote in news:1136934974.430378.213490 @g14g2000cwa.googlegroups.com: > I want build a 8jk antenna, but i don't find a good project on > internet. > Can anyone help me? http://www.hard-core-dx.com/nordicdx/antenna/wire/w8jk.html -- Dave Oldridge+ ICQ 1800667 VA7CZ Article: 220947 of rec.radio.amateur.antenna From: "Anthony Fremont" References: <1136148463.132269.164130@g49g2000cwa.googlegroups.com> <11rj9uu7bkogd37@corp.supernews.com> <11rlqiv2po14n6d@corp.supernews.com> Subject: Re: Dipoles and the rig's RF ground... Message-ID: Date: Wed, 11 Jan 2006 00:33:26 GMT "Dave Oldridge" wrote in message > I swear OH8OS used to MAKE his own band openings or 15 back in 65 when I > used to work him from VE8ML. He had a huge quad, 15 elements, I think, > pointed right in my direction. You just about can. Even with just two elements on 10, I worked several contacts from Houston that couldn't hear anyone else in the US. I really loved that antenna. Article: 220948 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Message-ID: Date: Wed, 11 Jan 2006 00:36:25 GMT Owen Duffy wrote: > On Tue, 10 Jan 2006 21:14:40 GMT, Owen Duffy wrote: > > >>On Mon, 09 Jan 2006 15:50:20 GMT, Cecil Moore wrote: >> >> >>>Ricke wrote: >>> >>>>If SETUP right , There the best HF I've ever used. >>> >>>Maybe the only one? :-) The G5RV, with tuner, is a pretty >>>good 80m, 40m, 20m, and 12m antenna. If the series section >>>is varied from 20 feet to 36 feet, it becomes a very good >>>all-HF-band antenna. With the addition of a parallel 1000pf >>>capacitor with the series section at 22 feet, on 75m my "G5RV" >>>has SWR of 1.3:1 and works as well as a 75m 1/2WL dipole. >> >>Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ? > > > I have made a mistake during my analysis, let me try again: Now you tell me after I spent 15 minutes replying to it. :-) The details are there so I won't repeat it here. > In that article, on 75m you model a feedpoint impedance of 36-j324, > 28' of 300 ohm ladder line, for a Z of 15+j4 (seems to indicate 48.2 > deg length of 300 ohm line with 0.007dB loss (optimistic)). > > At that point, were 50 ohm coax connected directly, the VSWR at the > load end of the 50 ohm coax would be 3, however you shunt the 17+j4 > with 1000pF to give a new Z of 17.3-j3.0 that results in a VSWR at the > load end of the 50 ohm coax of around 2.9, almost identical to the > case without the capacitor. > > Presumably when you say that the capacitor improves the VSWR on 75m, > you mean the VSWR on the coax. Did I miss something, how does the > capacitor improve the VSWR on 75m? What you missed is that the frequency must be changed to obtain the benefit. The capacitor is *not* installed at the 17+j4 point. It is installed at the 1/50 + j1/X admittance point. You can either increase the length of the feedline past the 17+j4 point to the 1/50 + j1/X admittance point or increase the frequency thus electrically lengthening the feedline to the 1/50 + j1/X admittance point. You cannot keep both of those values constant as you tried to do above. You already know what I am trying to say. I must not be saying it very well. When a parallel cap is used on a 75m screwdriver antenna to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e. slightly inductive. When a parallel coil is used, the screwdriver is tuned to 1/50 - j1/X, i.e. slightly capacitive. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220949 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: WTB Outbacker Mobile HF Antenna References: <11rr4922agp1acd@corp.supernews.com> Message-ID: <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> Date: Wed, 11 Jan 2006 00:38:21 GMT Jerry wrote: > How about someone who simply doesn't LIKE alcoholic drinks? :) That someone has never tasted Bailey's. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220950 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: <5tj8s1tvhfro9mn1kfahsueeg8mmdo0the@4ax.com> References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Wed, 11 Jan 2006 01:17:03 GMT On Wed, 11 Jan 2006 00:13:14 GMT, Cecil Moore wrote: >Owen Duffy wrote: >> Is this the antenna described at http://www.qsl.net/w5dxp/G5RV.HTM ? > >Nope, that's just an off-the-shelf vanilla G5RV. > >> In that article, ... > >Forget that article which only shows why the *standard* G5RV is >a fairly well matched antenna on 80m and 40m. But... in that article which recommends 28' of 300 ohm ladder line you say "To improve the 75m SWR, try installing a 1000pF capacitor (mica or doorknob) in parallel across the ladder line at the ladder line to coax junction. Remove the capacitor for all other bands." IMHO, just considering in isolation what is shown on that page there is something inconsistent about the Smith chart, the impedances, lengths, and assertions about the SWR improvement. ... >What I have done on my G5RV is find the point where the SWR circle >intersects the 1/50 conductance circle in the capacitive reactance >region on 3.8 MHz and install a 1000 pf parallel cap there. My series >section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm >SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz. This implies you are trying to "tune out" the shunt capacitive reactance at a point on the line where the shunt resistive component is 50... but you need the opposite sign of reactance reactance (so that the susceptances subtract), you need an inductive reactance in that case. If "your G5RV" has a feedpoint impedance of 36-j324 (that seems reasonable), your 22.5 ft. of Wireman #554 will transform that to 21.53-j53.33, and the VSWR in 50 ohm line connected at that point would be 5.3. A shunt capacitance CANNOT improve the 50 ohm VSWR at that point The effect of the shunt 1000pF capacitance is to change the impedance at the junction to around 3.6-j25, which would cause a VSWR of around 17 in the 50 ohm line. However: If the ladder line was around 31' in length, then the Z at that point would be around 21+j25 (equivalent to 50 ohms R in parallel with +43 ohms X), and a shunt 1000pF (~ -42 ohms X) capacitor would give nearly perfect VSWR on the 50 ohm line. In summary, in a general sense, if you want to use a shunt capacitor as you propose, you need to find length of line such that the admittance at that point is 1/50-jB (negative susceptance is inductive), and the correct shunt capacitor has a reactance of 1/B. Flawed explanation aside, the only way that 22.5' works is if your feedpoint Z is quite different to 36-j324. Owen -- Article: 220951 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> Date: Wed, 11 Jan 2006 01:34:30 GMT On Wed, 11 Jan 2006 00:36:25 GMT, Cecil Moore wrote: >You already know what I am trying to say. I must not be saying it >very well. When a parallel cap is used on a 75m screwdriver antenna >to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e. >slightly inductive. When a parallel coil is used, the screwdriver >is tuned to 1/50 - j1/X, i.e. slightly capacitive. Negative susceptances are inductive. An inductive reactance of j5 is a susceptance of 1/j5 or -j1/5. I agree with your words, the sign of the admittances is wrong. Owen -- Article: 220952 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: 8jk Message-ID: References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> <1136937028.162711.187430@o13g2000cwo.googlegroups.com> <1136943521.247512.281220@z14g2000cwz.googlegroups.com> Date: Wed, 11 Jan 2006 01:57:07 GMT On 10 Jan 2006 17:38:41 -0800, "ik7ytt" wrote: >i want build this antenna because seams to be the best choise for a >multiband array with gain and no loss(less than other) for field day >use. > >If i buld it for 20mt it should work also on 15-10mt without traps.And >in this way i can use fisshing pole to build it. > > >http://www.hard-core-dx.com/nordicdx/antenna/wire/w8jk.html >The project find on this page seams to be perfect, i do not understand >the lenght are for half element or the full element The diagram is not clear, is it. The basic End-fire W8JK uses two half wavelength dipoles spaced an eight of a wavelength. It has a half twist of the openwire line between the dipoles, and it is fed at the centre of that line. So, for 20m, each of the two dipoles will be about 10m long (end to end), and they will be spaced about 2.5m apart. (The diagram might lead you to think that each half of the dipole is around 10m, but that not correct.) Owen -- Article: 220953 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: 8jk Message-ID: References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> <1136937028.162711.187430@o13g2000cwo.googlegroups.com> <1136943521.247512.281220@z14g2000cwz.googlegroups.com> <1136946750.794798.222720@g49g2000cwa.googlegroups.com> Date: Wed, 11 Jan 2006 03:11:02 GMT On 10 Jan 2006 18:32:30 -0800, "ik7ytt" wrote: >Thanks for explain the diagram. >But now i have another doubt. >i have found on cebik home page an example of w8jk antenna. > >You can seee at http://www.cebik.com/fdim/fdim9.pdf on page 6 and 7 > >in this project the full element is 44'(13.2m) but spacing is 22' >(6.6m) Doesn't he say it is cut for the lowest frequency, and that is 30m or 10MHz) in Table 3? >So in this case the element is longher than 1/2wl ( i'm also reading >that the optimum is that the full element is from 1wl to 1.25wl, so >from 20m to 25m) and spacing is between 1/8 wl to 1/2wl. > >What is the best choise? >If element is to short i may have very low impedence -- Article: 220954 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <5tj8s1tvhfro9mn1kfahsueeg8mmdo0the@4ax.com> Message-ID: Date: Wed, 11 Jan 2006 04:17:17 GMT Owen Duffy wrote: > But... in that article which recommends 28' of 300 ohm ladder line you > say "To improve the 75m SWR, try installing a 1000pF capacitor (mica > or doorknob) in parallel across the ladder line at the ladder line to > coax junction. Remove the capacitor for all other bands." Yes, but installing the cap will raise the resonant frequency. >>What I have done on my G5RV is find the point where the SWR circle >>intersects the 1/50 conductance circle in the capacitive reactance ^^^^^^^^^^ >>region on 3.8 MHz and install a 1000 pf parallel cap there. My series >>section line is 22.5 ft. of Wireman #554 at that point. The 50 ohm >>SWR is reduced from about 5:1 to 1.3:1 on 3.8 MHz. > > This implies you are trying to "tune out" the shunt capacitive > reactance at a point on the line where the shunt resistive component > is 50... but you need the opposite sign of reactance reactance (so > that the susceptances subtract), you need an inductive reactance in > that case. Sorry, I misspoke. Where I said "capacitive reactance region" above, it should have been "inductive reactance region". > If "your G5RV" has a feedpoint impedance of 36-j324 (that seems > reasonable), your 22.5 ft. of Wireman #554 will transform that to > 21.53-j53.33, and the VSWR in 50 ohm line connected at that point > would be 5.3. "If" is the important word. My G5RV is obviously different from your values. It's made out of insulated wire and I'm not sure it is exactly 102 feet long. > Flawed explanation aside, the only way that 22.5' works is if your > feedpoint Z is quite different to 36-j324. And it is obvious that's the case. The "450" ohm ladder-line is 22.5 ft. long and a 1000 pf capacitor resonates it on 3.8 MHz. Whatever the feedpoint impedance needs to be to cause those conditions, that's what it is. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220955 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Message-ID: Date: Wed, 11 Jan 2006 04:25:59 GMT Owen Duffy wrote: > Cecil Moore wrote: >>You already know what I am trying to say. I must not be saying it >>very well. When a parallel cap is used on a 75m screwdriver antenna >>to achieve 50 ohms, the screwdriver is tuned to 1/50 + j1/X, i.e. >> ^ should be - >>slightly inductive. When a parallel coil is used, the screwdriver >>is tuned to 1/50 - j1/X, i.e. slightly capacitive. >> ^ should be + > Negative susceptances are inductive. An inductive reactance of j5 is a > susceptance of 1/j5 or -j1/5. > > I agree with your words, the sign of the admittances is wrong. Yes, you are correct - sorry. But it now seems that you understand what I was trying to say. If one takes an ordinary G5RV and installs a parallel 1000pf capacitor at the coax/twinlead junction, one will raise the resonant frequency and lower the SWR on the coax for 75m operation. Very close to 50+j0 ohms can be achieved on 75m through that simple act. When I lived in AZ, I switched that cap in automatically using a relay and the frequency output signal on my IC-745. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220956 of rec.radio.amateur.antenna From: "george tibbetts" Subject: shorty forty (G5RV) little brother Message-ID: Date: Wed, 11 Jan 2006 04:34:14 GMT Just read all msg on the g5rv question (wow) so let me introduce my problem - I bought a shorty forty 2ys ago at a hamfest, now Im ready to use it: I have two poplar trees about 150ft fm house about sixty feet apart (perfect) and a garden shed underneath almost centered. The shorty forty is fed with (not measured) twin lead with a female coupler for a pl259 to get to house. I have about 180ft of catv (75 ohm) . Question: should I use a 6 to 1 balun attached to shed or should I just attach the catv to the ladder line and let it go. The vendor of the shorty forty assured me that I just had to attach normal 50 ohm coax to the connector and I was ready to go. of course I have a good tuner and used it many years with a van gorden g5rv and did great but the van gordon came with a balun at the end of the twin lead. thanks - george Article: 220957 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: shorty forty (G5RV) little brother References: Message-ID: Date: Wed, 11 Jan 2006 04:41:00 GMT george tibbetts wrote: > The shorty forty is > fed with (not measured) twin lead with a female coupler for a pl259 to get > to house. I have about 180ft of catv (75 ohm) . Question: should I use a 6 > to 1 balun ... Forget the 6:1 balun - install a 1:1 current choke-balun at the coax/twinlead junction. The W2DU type works well. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220958 of rec.radio.amateur.antenna From: 'Doc Subject: Re: Home Made Hazer Ideas? References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> <35Fwf.5377$%W1.4601@newsread2.news.atl.earthlink.net> Message-ID: Date: Wed, 11 Jan 2006 05:39:21 GMT Doug, Oops, tapered? Hmm, that's gonna be fun. Sounds like there would have to be some type of 'stand-off' support and a constant rail seperation for the hazer to ride on. I think I'd have to recommend that you swap towers, or ideas. 'Doc (At 'Big Mac' on the outside looking in!) Article: 220959 of rec.radio.amateur.antenna From: "David J Windisch" References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> Subject: Re: 8jk Message-ID: Date: Wed, 11 Jan 2006 11:12:27 GMT Hi, all concerned: The W8JK antenna can keep its same general broadside pattern when the lengths and spacing vary widely. So, you can build one to fit the space available, and you need to pay attention only to keeping the 4 lengths of element-wire close to the same length, and to crossing the phasing line over between element feedpoints**. It will work well over a 3-to-1 frequency range. Element maximum-currents and voltages can be quite high, so use the largest practicable wire size, and good insulators. Exact lengths or "resonance" do not seem to affect patterns. It is probably easier to use open-wire feedline. To make the antenna easier to tune, you can vary the feedline length between the transmitter and the antenna. Make your feedline "tune the antenna". Modeling it with EZNEC shows that, at lower frequencies, it can have more radiation at lower angles than some other simple antennas at the same height above ground, and that shifting the feedpoint away from the center of the phasing line produces a uni-directional pattern. I hope this helps. 73, Dave, N3HE ** uncrossed will make it a double-lazy-H ;o) "wildboy" wrote in message news:1136934974.430378.213490@g14g2000cwa.googlegroups.com... >I want build a 8jk antenna, but i don't find a good project on > internet. > Can anyone help me? > Article: 220960 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Any experience with the G5RV multiband wire antenna? Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Date: Wed, 11 Jan 2006 11:26:24 GMT On Wed, 11 Jan 2006 04:25:59 GMT, Cecil Moore wrote: >Yes, you are correct - sorry. But it now seems that you understand >what I was trying to say. If one takes an ordinary G5RV and >installs a parallel 1000pf capacitor at the coax/twinlead junction, >one will raise the resonant frequency and lower the SWR on the >coax for 75m operation. Very close to 50+j0 ohms can be achieved >on 75m through that simple act. When I lived in AZ, I switched that >cap in automatically using a relay and the frequency output signal >on my IC-745. OK. I played around a bit using the feedpoint impedances that I modelled for my "Feeding the G5RV" article. With 31' of 554, I needed about 2000pF to "tune" it for low 50 ohm VSWR at 3.6MHz. I plotted the impedance presented to the coax for a range of frequencies from 3.5 to 3.8MHz, they are at http://www.vk1od.net/temp/G5RV-W5DXP.GIF . The Smith chart is normalised to 50 ohms. The solution seems fairly narrow band, the VSWR at 3.55 was 6, at 3.6 it was 1.3, and at 3.65 it was 5. Of course, implementations will have slight differences in actual feedpoint impedances, and the outcome is very sensitive to slight differences in feedpoint Z. This "no-tuner" matching scheme will probably need significant customisation for each implementation. Owen -- Article: 220961 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Wed, 11 Jan 2006 12:26:53 +0000 (UTC) Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> "Owen Duffy" wrote > Of course, implementations will have slight differences in actual > feedpoint impedances, and the outcome is very sensitive to slight > differences in feedpoint Z. This "no-tuner" matching scheme will > probably need significant customisation for each implementation. > ========================================== The World-famous G5RV. --------------------------------- What everyone appears to forget, is that Zo of the balanced twin-line section, on all bands except at 14.15 MHz, has a considerable affect on feedpoint impedances, swr, losses, etc. When describing systems and performance nobody ever mentions what Zo of the feedline actually is. Omission of Zo reduces any following discussion to blythe, innocent nonsense. R.L.Varney himself never gave a value to Zo. He didn't need to. He was concerned mainly with 14.15 MHz. It would be unfair to accuse him of not understanding the serious effects of Zo on other bands. ---- Reg. Article: 220962 of rec.radio.amateur.antenna From: richardharrison@webtv.net (Richard Harrison) Subject: Re: Recommendation for 915MHz omni antenna Date: Wed, 11 Jan 2006 08:53:55 -0600 Message-ID: <27102-43C51C03-1@storefull-3253.bay.webtv.net> References: David weote: "How do you get an omni-directional pattern from this antenna?" In a point to multipoint system, only the central station needs an omni antenna. One orderly radio data acquisition system operates half-duplex. Only one station at a time transmits, and then only when called upon to do so. A radio master interrogates remote stations within its reach, addressing them by name, rhen listens for their response. Only a single radio frequency is needed as remote stations don`t initiate transmissions until callef upon. In this master-slave relationship, there is no competition within the system for radio time. The radio master can conveniently use an omnidirectional antenna as it communicates with slaves on various azimuths. The slaves only communicate with the master, even to communicate with each other. The slaves each have a directional antenna aimed at the master. A directional antenna improves signal to noise ratio when transmitting and when receiving. Great gain and directionality, though desirable, may be necessary only when very low transmitter power must be used.. The long-boom directional loop array may have a gain of 20 dB. But, a 3-element Yagi can give a 5 dBd gain which may be plenty. This gain is almost equivalent to cutting the path length by half (6 dB). The Yagi is close-spaced. With only 3 elements it is small and simple to build. Normal narrow-band receivers are very sensitive so that very weak signals are sufficient if noise and interference are not severe. Higher gain antennas can be used as needed at remote sites on a case by case basis. I built such a system decades ago and it is still in use. Best regards, Richard Harrison, KB5WZI Article: 220963 of rec.radio.amateur.antenna From: "Earl Needham" Subject: Re: WTB Outbacker Mobile HF Antenna Date: Wed, 11 Jan 2006 09:10:22 -0700 Message-ID: <11sabfebrvtljda@corp.supernews.com> References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> "Cecil Moore" wrote in message news:1sYwf.5083$fb4.758@newssvr14.news.prodigy.com... > Jerry wrote: > > How about someone who simply doesn't LIKE alcoholic drinks? :) > > That someone has never tasted Bailey's. :-) > -- > 73, Cecil http://www.qsl.net/w5dxp Or Amaretto, or Drambuie, or Captain Morgans in a vanilla Pepsi, or... Earl -- Earl Needham Clovis, New Mexico USA Article: 220964 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Message-ID: Date: Wed, 11 Jan 2006 16:45:37 GMT Owen Duffy wrote: > I played around a bit using the feedpoint impedances that I modelled > for my "Feeding the G5RV" article. With 31' of 554, I needed about > 2000pF to "tune" it for low 50 ohm VSWR at 3.6MHz. I'm just reporting what it took for my actual antenna under the existing conditions at my QTH. The cap is actually 950 pf for a minimum SWR of 1.3:1 on 3.9 MHz. The optimum value of the cap would no doubt change at lower frequencies. With 22.5' of Wireman #554 and a 950 pf cap, the 3:1 bandwidth is 145 kHz. Adding sections of ladder-line lowers the resonant frequency. Incidentally, this is a method for modifying the G5RV to work, not only without a tuner, but with built-in tuners. When using a built-in tuner, the antenna configuration doesn't have to be changed as often. My IC756PRO will tune my present configuration >from 3.72-4.0 MHz. or 280 kHz. > I plotted the impedance presented to the coax for a range of > frequencies from 3.5 to 3.8MHz, they are at > http://www.vk1od.net/temp/G5RV-W5DXP.GIF . The Smith chart is > normalised to 50 ohms. The solution seems fairly narrow band, the VSWR > at 3.55 was 6, at 3.6 it was 1.3, and at 3.65 it was 5. Changing the length of the series section will shift the resonant frequency. I can vary mine from 22.5 ft. to 38.5 ft for a near- perfect SWR on all HF ham frequencies. > Of course, implementations will have slight differences in actual > feedpoint impedances, and the outcome is very sensitive to slight > differences in feedpoint Z. This "no-tuner" matching scheme will > probably need significant customisation for each implementation. IMO, that is what ham radio is all about - warm up the old MFJ-259B and get with the program. :-) -- 73, Cecil http://www.qsl.net/w5dxp Article: 220965 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Message-ID: <5Paxf.49818$BZ5.41181@newssvr13.news.prodigy.com> Date: Wed, 11 Jan 2006 16:58:41 GMT Reg Edwards wrote: > R.L.Varney himself never gave a value to Zo. He didn't need to. He was > concerned mainly with 14.15 MHz. It would be unfair to accuse him of > not understanding the serious effects of Zo on other bands. However, in The ARRL Antenna Compendium #1, he did describe the matching section well enough to calculate his Z0. It is #14 copper open-wire separated by 1.75 inches. I'll bet that's an improvement over 300 ohm twinlead. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220966 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Wed, 11 Jan 2006 19:41:08 +0000 (UTC) Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> <5Paxf.49818$BZ5.41181@newssvr13.news.prodigy.com> > Reg Edwards wrote: > > R.L.Varney himself never gave a value to Zo. He didn't need to. He was > > concerned mainly with 14.15 MHz. It would be unfair to accuse him of > > not understanding the serious effects of Zo on other bands. > > However, in The ARRL Antenna Compendium #1, he did describe the > matching section well enough to calculate his Z0. It is #14 > copper open-wire separated by 1.75 inches. I'll bet that's > an improvement over 300 ohm twinlead. > -- > 73, Cecil ========================================== Cec, the facts are, G5RV never mentioned Zo, either because he never attached any importance to it, or he didn't understand its relevance to other bands. When considering other than 14.15 MHz perhaps he should have done. In any event, everybody else has followed suit. Now we have the situation where dozens of people are busily seriously comparing all-band versions, one with another, and unknown to each other they are all using different value Zo transmission lines. Many of those who purchased the antennas, or just copied G5RV's construction, havn't the foggiest idea what their particular Zo is. Yet, from an analysis point of view, which you are involved with, it is a crucial matter. Your own Zo is a non-standard 375 ohms because you measured it. Yet you describe its performance to others as if everybody else's Zo is the same, whereas there is no hope of anybody else reproducing your particular results. Its all a load of nonsense! If anybody, at this very late stage in the art, should still wish to acquaint themselves with the less than mediocre performance of a G5RV, then download program DIPOLE3 from website below. DIPOLE3 is a general purpose program which deals with a dipole of any length, at any frequency, plus balanced-twin feedline of any length and any Zo, plus balun, plus coax line of any length and Zo, plus L-tuner. So it happens to include a G5RV. All the data for the original G5RV can be inserted in the program by depressing one key. Modifications to the system, such as changes in Zo, can easily be done and changes in performance immediately seen. The final important output figure is overall loss between transmitter and radiated power. Individual losses in the antenna, in the two transmission lines, and in the tuner, are reported seperately. Even the tuner L and C settings and their circuit locations are predicted. It is very easy to sweep over the HF frequency range to check when low swr happens to fall into amateur bands. (Unfortunately it doesn't do this very often.) It is also easy to change the length of transmission line (as Cecil recommends and advertises) to try to obtain an swr of less than 2:1. But you can use any dipole length other than 102-feet to play with this useful aspect. Accuracy is better than needed for the intended purposes and is generally as good as the accuracy of program input data. There is only one known trivial bug which occurs when dipole length is extremely short compared with wavelength. But clearly this is not of consequence. What more could you want from a G5RV? There's nothing to do but erect it and then compare it with a dipole of any other length with an open wire feedline of thick wire, of no particular length, all the way to the shack. Plus a choke balun. I'm still on Red, South African, Western Cape. Download DIPOLE3. Its free to USA citizens. ---- ........................................................... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp ........................................................... Article: 220967 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Query.. Date: Wed, 11 Jan 2006 20:25:22 +0000 (UTC) Message-ID: References: <43bd1032$0$82676$ed2619ec@ptn-nntp-reader03.plus.net> <11s63d3hf8jjqe3@corp.supernews.com> Unless a self-respecting radio amateur wishes to set up a point-to-point communications link, he would not consider a rhombic which wastes half the transmitter power in a resistor. How popular are rhombics, such as you describe, amongst amateurs? There are, of course, some rich, perhaps contest participating amateurs, with time any money to burn. I have no objection to their existence. They are very welcome to the fraternity. They demonstrate just what can be achieved. ---- Reg. Article: 220968 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Any experience with the G5RV multiband wire antenna? Date: Wed, 11 Jan 2006 21:37:15 +0000 (UTC) Message-ID: References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> <5Paxf.49818$BZ5.41181@newssvr13.news.prodigy.com> Now Cec, your reference to my use of the English language, which you well understand, is an admission that you have lost the argument - whatever that may be. And you, more than most people, should realise that it's fatal to use ARRL publications as Bibles. The facts are, the Zo of the G5RV trannsmission line is indeterminate. Everybody has a different but unknown value. And it follows that, so are all the interminable discussions on the subject which take place on this and other newsgroups. Hardly educational. They approach amusing nonsense! But no doubt you will wish to further dig yourself in and have the last word. Go ahead! ;o) ---- Reg. Article: 220969 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Dipoles and the rig's RF ground... Message-ID: <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> Date: Wed, 11 Jan 2006 21:37:32 GMT On 11 Jan 2006 01:09:41 -0800, nm5k@wt.net wrote: >>Where are the losses in a Ladder- >>Line fed system? .... > >The tuner that is usually used offsets the advantage >of the line itself. Sure, on paper you shouldn't really >be able to notice it. But I do when I test it. It's actually >measureable on an S meter when doing A/B comparisons. >Or at least it was for me when using a 989c tuner >and minimum inductance vs coax fed. You are telling us that you have evaluated the loss of a MFJ-989C antenna tuner + open wire line vs coax by on air A/B tests using the S-meter as your indicator. Presumably you used exactly the same antenna, how are you sure that the feedline wasn't an active part of the antenna, was the measurement made over an ionospheric path, was the A/B comparison made at different times when other things may have changed? What would be your confidence limits on such a experiment? If you recorded your results, the variance would be revealing. I suggest that the noise in your experiment would probably swamp the true difference between your A and B configuration, and therefore your conclusion might not be sound. Your observation is (as you note) different to "on paper" expectations, that might be reason to re examine the experimental setup in search of an explanation. Owen -- Article: 220970 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: 8jk Date: Wed, 11 Jan 2006 14:17:42 -0800 Message-ID: <11sb107cm3i6sa0@corp.supernews.com> References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> David J Windisch wrote: > . . . > Modeling it with EZNEC shows that, at lower frequencies, it can have more > radiation at lower angles than some other simple antennas at the same height > above ground, and that shifting the feedpoint away from the center of the > phasing line produces a uni-directional pattern. > . . . I don't think you'll see both those effects (lower radiation angle and unidirectional pattern) at the same time. You'll find that the elevation pattern of small to moderate sized Yagis, log periodic antennas, and most other horizontal arrays is essentially the same as that of a dipole, at least at the lower elevation angles. The reason is that most horizontal arrays have a broad free space pattern in the vertical plane -- not that much different than a dipole, in the forward array direction. The W8JK is unusual in that respect. Its free space vertical pattern is noticeably narrower than most other moderately sized horizontal arrays, so it has a narrower elevation pattern when mounted over ground, too. The net result is a greater concentration of radiation at lower angles. Unfortunately, the cost of this narrower vertical pattern is a bidirectional horizontal pattern, resulting in half the applied power being wasted unless you happen to be talking to two oppositely-located people at once. So for a given power input, the gain is 3 dB less than a unidirectional antenna with the same lobe width, or the same as a unidirectional antenna with a considerably wider lobe. The only way to fairly compare the gains is by modeling and looking at the field strength of the antennas at the azimuth and elevation angle of interest. (Loss must be realistically included in the models, too.) It's entirely possible that the advantage of concentration of radiation at lower angles is more than offset by the lower gain due to its bidirectionality and/or loss (see the next paragraph). Of course, you can change the feed as Dave suggests to get a unidirectional pattern. But then your free space elevation pattern becomes a broad cardioid, and you end up with a dipole-like elevation pattern over ground. Among the advantages of the W8JK are simplicity and the fact that the pattern changes very little over very wide bandwidths. On the down side are the bidirectionality and, particularly when spacing is close, a low feedpoint resistance and rapid change in feedpoint impedance with frequency. The feedpoint resistance can be low enough that wire loss becomes a concern, and if not, matching network and perhaps even feedline loss can become significant. You're almost certain to be running a very high SWR on the feedline, so very low loss line is a must. Roy Lewallen, W7EL Article: 220971 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Dipoles and the rig's RF ground... Date: Wed, 11 Jan 2006 14:27:58 -0800 Message-ID: References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> ORIGINAL MESSAGE: "Owen Duffy" wrote in message news:00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com... You are telling us that you have evaluated the loss of a MFJ-989C antenna tuner + open wire line vs coax by on air A/B tests using the S-meter as your indicator. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You can do a pretty good evaluation of a tuner's loss by putting your hand on the cabinet after running a few minutes. Just imagine a 25, 50 or whatever watt resistor in there dissipating the same heat. One needs to calibrate one's hand, of course. :-) Bill, W6WRT Article: 220972 of rec.radio.amateur.antenna From: "DOUGLAS SNOWDEN" References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> <35Fwf.5377$%W1.4601@newsread2.news.atl.earthlink.net> Subject: Re: Home Made Hazer Ideas? Message-ID: Date: Thu, 12 Jan 2006 00:14:39 GMT Yes, I am starting to think about just tilting the whole mess up at one time. Doug "'Doc" wrote in message news:dS0xf.5187$4o7.3172@newssvr24.news.prodigy.net... > Doug, > Oops, tapered? Hmm, that's gonna be fun. Sounds like there would > have to be some type of 'stand-off' support and a constant rail > seperation for the hazer to ride on. I think I'd have to recommend > that you swap towers, or ideas. > 'Doc > (At 'Big Mac' on the outside looking in!) Article: 220973 of rec.radio.amateur.antenna From: "Steve Nosko" Subject: Re: radar and health ? digressing to keyless remotes... Date: Wed, 11 Jan 2006 17:52:01 -0600 Message-ID: References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <9AqdnWDnPbDRsFneSa8jmw@karoo.co.uk> Some thoughts inserted in Dan's comments...*** "Dan Andersson" wrote in message news:9AqdnWDnPbDRsFneSa8jmw@karoo.co.uk... > Thierry wrote: > > ... > > My company has installed a Radar Tower for Port survaillence. The tower > > is about 50 meter height on top of the of a 3 stories building roof and > > my office building just below the tower on the same level, 20 meter away > > from the tower. At the same time, the surrounding is my working area ( > > Jetty Terminal for ships loading and unloading activities ). I can say > > that I'll be around that area 12 hours a day for another 20 years. > > My question: > > Is it safe to work in that area???? > > Thanks in advance > > Thierry > > So, what about Radar then... > > First, There are two "kind" of RF radiation, non-ionizing and ionizing and > effects emanating from very high voltage nearby different materials. *** Perhaps a typo, but the ionizing type is not a kind of RF radiation. Ionizing radiation is nuclear radiation. This radiation is able to strip electrons (and other particles) from atoms. RF does not do this as we use it. It is unfortunate that we use the term "radiation" for both things. In any case, it is not part of the original question. > Normally, non-ionising is to be more or less compared to sun light.... *** RF, Light is Electromagnetic radiation and produces, as far as we know and can be proved, Heat. > As long as you are not overheating, there should be no harmful effects on > you. ... *** Widely agreed, yet feared by many. > Now, radar radiation ...sometimes with stupidly high power.... ** Not to the people USING it. > If you are standing near a RF radiating radar station, the average energy is > what heats you up ... *** Regardless of where/how you receive RF power, it produces a heating effect. Standing in an open field, you are picking up RF from EVERY transmitter within ear-shot (so to speak) and you have RF currents in your body, but of course, the heat generated is infinitesimal. Tests have been done to measure the low, yet measurable actual heating of things such as the human face in the RF field of hand-held radio like power. > Some frequencies are really bad > for us because different parts of our bodies absorbs different amount of > energy on different frequencies. *** The effect is that of heating and the most prominant effect is the heating of the water content in things - us included. Water (H20) absorbs RF best around 900 MHz and again around 2500 MHz. There may be more frequencies, but these are the two used in microwave ovens (900 earlier and 2400 now - I believe). When it does absorbe it ( as opposed to reflecting it, which it may do depending on how good the impedance match is) the water heats. The old (possibly urban myth) story is of the radar techs up at the old Dew Line Early warning radars would stand in fornt of the High power radar antennas to warm up when working outside. The standard joke is that they had small families after that... > Let's take a party example... Many key fobs, alarm buttons for car locks > etc, operates on 418MHz. It happens to be approximately where a normal head > are resonating... Try walking just about out of range for your alarm/lock > button for your car, point the key fob against your head and press the > unlock key, voila, in most cases, you increase the range of the key fob.... > Dan / M0DFI *** Mine is around 320 MHz. I seriously doubt that the head resonates there, or has much of a resonance to speak of at any frequency. This "range extending of the keyless remote" is easily duplicated by various placements of your other hand, arm and other parts of the body, near the remote. I play with it often walking across the parking lot to the car. It can be best explained considering that being conductive, the body can pick up RF from the fob and be an added part of the antenna in a quasi-parasitic-element manner. The "antenna" in the fob is, at best, an extremely poor one (not being anywhere near 1/4 or 1/2 a wavelength, nor being a loaded antenna that is matched to the transmitter) and any help it gets will frequently be observed as positive. This effect is very dependant on things like polarization of the auto's receive antenna (if there is one with a recognizable polarization), polarization of "you as an antenna", direction (as the transmit pattern will most certainly be directional as well as the receive pattern), and probably innumerable other complexities of the RF environment you happened to be immersed in. Any kind of a conductor can be brought close to the fob and have a similar effect. I've done it with long screwdrivers and pieces of wire. Careful placement of a half wave wire can achieve astounding range....comparatively (to me, anyway, but then, there are those that say I am easily amused). Nerd that I am, it's fun to see how much range you actually can get...just for the bleep of it. I should get a life at times. (:-) Please no agreement. 73, Steve, K,9.D'C;I Oh yea...the origainsl Radar near the office question. Do a search on something like the Russian radar illumination of the American Embassy. I believe there are those that claim the Americans which the Russians were radiating with Radar got irritable or some such symptom(s). 73 Article: 220974 of rec.radio.amateur.antenna From: "Jerry" References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> Subject: Re: WTB Outbacker Mobile HF Antenna Message-ID: Date: Wed, 11 Jan 2006 19:35:05 -0500 "Cecil Moore" wrote in message news:1sYwf.5083$fb4.758@newssvr14.news.prodigy.com... > Jerry wrote: >> How about someone who simply doesn't LIKE alcoholic drinks? :) > > That someone has never tasted Bailey's. :-) > -- > 73, Cecil http://www.qsl.net/w5dxp What I don't know at this stage won't hurt me. Not to be argumentive, but I have heard that before. "But you'll LOVE this beer or that wine or that whiskey". I can't tell the difference; the "great" beer or the wonderful wine tastes the same as the "cheap" (?) stuff. BARF! ;) The Coca Cola still wins! LOL! 73 J Article: 220975 of rec.radio.amateur.antenna From: David Subject: Starting point for antenna design Message-ID: Date: Thu, 12 Jan 2006 00:39:01 GMT Can someone explain to me how a new antenna design is started. Do you take an initial standard design and then enter it into a modeling program and optimize it for the required parameters ? Is there a suitable reference book that would explain this process. I am thinking about the Cebik antenna modeling book but think this may only cover how to model and change an existing design,would it cover how to come up with the initial design in the first place ? Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm diameter elements. Is there a standard formula that would be used to calculate initial lengths and distances between elements. Then you enter this design into say EZNEC and use the optimizer to tweak the design. Thanks in advance Regards David Article: 220976 of rec.radio.amateur.antenna From: Bob Miller Subject: Re: Any Such Coax Switch? Message-ID: References: Date: Thu, 12 Jan 2006 00:41:30 GMT On Wed, 11 Jan 2006 17:00:34 -0700, jimbo wrote: >I have two, 2 meter radios, one in my basement shack and one in my >computer room on the second floor. I have one 2 meter antenna located >in the third floor attic. I would like a switch that would switch the >antenna between the two radios and I want the radio that is not >connected to the antenna to be connected to a dummy load. > >Maybe I haven't looked hard enough, but all of the switches I have >found so far, switch multiple antennas to one radio and ground the >unused antenna(s). > >Thanks for any help, jimbo There's an mfj switch, MFJ-1700C, that handles six antennas on one side, six transceivers on the other. Rated up to 30 mhz, so may or may not be right for 2 meters. bob k5qwg Article: 220977 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: WTB Outbacker Mobile HF Antenna Date: Wed, 11 Jan 2006 16:52:27 -0800 Message-ID: References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> ORIGINAL MESSAGE: > "Cecil Moore" wrote in message What I don't know at this > stage won't hurt me. Not to be argumentive, but I have heard that before. > "But you'll LOVE this beer or that wine or that whiskey". I can't tell > the difference; the "great" beer or the wonderful wine tastes the same as > the "cheap" (?) stuff. BARF! ;) The Coca Cola still wins! LOL! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I used to think that way too. Only bought the cheap stuff until one day someone gave me a bottle of Glenlivet scotch. I rarely buy it because I don't want to mortgage the house, but now I *do* know the difference. :-) Bill, W6WRT Article: 220978 of rec.radio.amateur.antenna From: "David Thompson" Subject: Rax bassett and Savoy Electronics Message-ID: Date: Thu, 12 Jan 2006 01:21:17 GMT Does anyone in South Florida know what happened to Rex Bassett and or Savoy Electronics of Ft. Lauderdale? Rex was making big antennas before WW II plus had a line of big (mainly commercial) transmitters). In the 1950's Rex did some pioneer work on mobile antenna coils filled with helium. Later he sold Bassett 80 to 10 antennas (coils filled Helium) thru Savoy Electronics. He wrote for CQ and advertised in CQ and QST. I suspect Rex has long since passed away but can someone clue me in on his history? 73 Dave K4JRB Article: 220979 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: SF Solar Flux Values: What's A Good Value For General SWL Date: Wed, 11 Jan 2006 17:00:00 -0800 Message-ID: References: ORIGINAL MESSAGE: "Robert11" wrote in message news:Iq6dnfY5nbZlBljeRVn-uA@comcast.com... > Hello: > > What's a "good" value for the SF Solar Flux values reported for general > SWL (30 MHz and below) ? > > Is it freq. dependent ? How ? > > Thanks, > B. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It would take hours to really answer your question fully, but I think I can help: For most hams, when the flux gets above 100, things are picking up. Above 125, you'll hear comments about how great the bands are. Above 150, you can do DXCC in a week running QRP. Above 175, you'll ask the wife to call in sick for you so you can chase DX. Above 200, you won't have to call in sick anymore because you quit your job. How's that? :-) Bill, W6WRT Article: 220980 of rec.radio.amateur.antenna From: "kd5sak" References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> Subject: Re: WTB Outbacker Mobile HF Antenna Message-ID: Date: Thu, 12 Jan 2006 01:31:28 GMT "Bill Turner" wrote in message news:dq498d016ak@enews4.newsguy.com... > ORIGINAL MESSAGE: > I used to think that way too. Only bought the cheap stuff until one day > someone gave me a bottle of Glenlivet scotch. I rarely buy it because I > don't want to mortgage the house, but now I *do* know the difference. :-) > > Bill, W6WRT > > Have to agree, bought some really high dollar Scotch for New Years Eve in 1954 while in Japan. Flavor wasn't the same but it was as smooth as chocolate milk. I was asleep before midnight. Had to quit that sort of thing though, my Dad was alcoholic and I figured I'd probably inherited the gene. Harold Burton Article: 220981 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Dipoles and the rig's RF ground... Date: Wed, 11 Jan 2006 18:44:00 -0800 Message-ID: <11sbgjhmh57cvae@corp.supernews.com> References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> Bill Turner wrote: > > You can do a pretty good evaluation of a tuner's loss by putting your hand > on the cabinet after running a few minutes. Just imagine a 25, 50 or > whatever watt resistor in there dissipating the same heat. > > One needs to calibrate one's hand, of course. :-) > > Bill, W6WRT > I disagree. I'd venture to guess that the average output power of a 100 watt PEP sideband rig is no more than about 10 watts unless heavy compression is being used. And I think you'll find that a 10 watt resistor inside a typical tuner cabinet -- representing loss of all the transmitted power -- will make a barely noticeable difference in the cabinet temperature. Add to that the fact that the thermal time constant of the tuner is probably longer than the typical transmitting session, so the power needs to be averaged over the receiving periods, too. If you're running a kW, you're up to 100 watts or so during transmit only. But can you tell the difference with your "calibrated" hand between 1 dB loss in the tuner (25 watts), 3 dB loss in the tuner (50 watts), or 100% of the power lost in the tuner (100 watts)? I'd love to see the results of a double-blind study where a measured tuner loss is compared with an estimate made using Bill's method. But I think the chances of that are about the same as finding a double-blind study of the audio quality enhancement of $1000 speaker cables. Roy Lewallen, W7EL Article: 220982 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Starting point for antenna design Date: Wed, 11 Jan 2006 18:53:06 -0800 Message-ID: <11sbh4k4gvisc1d@corp.supernews.com> References: A very good source of starting designs is _Yagi Antenna Design_ by James Lawson, W2PV, published by the ARRL. It clearly illustrates the various tradeoffs which can be made in Yagi design, and gives lots of alternatives. There is no "ideal" design, since there are so many tradeoffs to be made -- gain, front/back ratio, bandwidth, size, which you can't maximize all at once. EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak the design yourself. People who have used optimizing programs have told me they've often been able to improve on the "optimized" design by hand tweaking with EZNEC. Roy Lewallen, W7EL David wrote: > Can someone explain to me how a new antenna design is started. Do you > take an initial standard design and then enter it into a modeling > program and optimize it for the required parameters ? > > Is there a suitable reference book that would explain this process. I am > thinking about the Cebik antenna modeling book but think this may only > cover how to model and change an existing design,would it cover how to > come up with the initial design in the first place ? > > Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm > diameter elements. > > Is there a standard formula that would be used to calculate initial > lengths and distances between elements. Then you enter this design into > say EZNEC and use the optimizer to tweak the design. > > Thanks in advance > > Regards > > David > > Article: 220983 of rec.radio.amateur.antenna From: "Jerry" References: <11rr4922agp1acd@corp.supernews.com> <1sYwf.5083$fb4.758@newssvr14.news.prodigy.com> Subject: Re: WTB Outbacker Mobile HF Antenna Message-ID: Date: Wed, 11 Jan 2006 22:06:37 -0500 "kd5sak" wrote in message news:Qjixf.119$H71.20@newssvr13.news.prodigy.com... > > "Bill Turner" wrote in message > news:dq498d016ak@enews4.newsguy.com... >> ORIGINAL MESSAGE: >> I used to think that way too. Only bought the cheap stuff until one day >> someone gave me a bottle of Glenlivet scotch. I rarely buy it because I >> don't want to mortgage the house, but now I *do* know the difference. :-) >> >> Bill, W6WRT >> >> > Have to agree, bought some really high dollar Scotch for New Years Eve in > 1954 while in Japan. Flavor wasn't the same but it was as smooth as > chocolate milk. I was asleep before midnight. Had to quit that sort of > thing though, my Dad was alcoholic and I figured I'd probably inherited > the gene. > > Harold Burton That's just it for me. I don't want to run the risk, and after seeing what it did to friends and relatives as well, it made up my mind in high school. Tried it. It tasted AWFUL no matter what, so I prefer a Coke. Oh, if someone insists I take a sip with him, I will. But since I simply do not like the taste of alcoholic drinks, I simply drink enough to satisfy the buyer and let it go. I just don't like it the same way some people don't like broccoli or cauliflower and I never will. :) 73 Jerry > > Article: 220984 of rec.radio.amateur.antenna From: Gene Fuller Subject: Re: radar and health ? digressing to keyless remotes... References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <9AqdnWDnPbDRsFneSa8jmw@karoo.co.uk> Message-ID: Date: Thu, 12 Jan 2006 03:24:29 GMT Steve, Your assertion is simply not correct. You may be thinking of particle radiation, such as electron (beta), neutron, proton, alpha, cosmic, etc., but pure photon radiation can certainly be "ionizing". A well-known example is ordinary medical x-rays. Ionizing photons would not typically be called "RF", but there is no difference other than the energy levels. (I spent so much time in the early stages of my career dealing with intense sources of ionizing radiation (photons) that I still glow in the dark.) Back to the original question, ordinary radar is clearly not "ionizing". Not a good idea to be too close, due to possible thermal effects, but otherwise no big deal. 73, Gene W4SZ Steve Nosko wrote: > Some thoughts inserted in Dan's comments...*** > > > "Dan Andersson" wrote in message > news:9AqdnWDnPbDRsFneSa8jmw@karoo.co.uk... > >> >>First, There are two "kind" of RF radiation, non-ionizing and ionizing and >>effects emanating from very high voltage nearby different materials. > > > *** Perhaps a typo, but the ionizing type is not a kind of RF > radiation. Ionizing radiation is nuclear radiation. This radiation is able > to strip electrons (and other particles) from atoms. RF does not do this as > we use it. It is unfortunate that we use the term "radiation" for both > things. In any case, it is not part of the original question. Article: 220985 of rec.radio.amateur.antenna From: "Crazy George" References: <11sbh4k4gvisc1d@corp.supernews.com> Subject: Re: Starting point for antenna design Date: Wed, 11 Jan 2006 21:34:26 -0600 Message-ID: <43c5ce5c@kcnews01> Roy: Whatever happened to YO? Was that one of your creations which you stopped selling? Or was it Beezley's? -- Crazy George W5VPQ My real address is my ham call ARRL.NET The ATTGlobal is a SPAM trap. "Roy Lewallen" wrote in message news:11sbh4k4gvisc1d@corp.supernews.com... >A very good source of starting designs is _Yagi Antenna Design_ by James >Lawson, W2PV, published by the ARRL. It clearly illustrates the various >tradeoffs which can be made in Yagi design, and gives lots of alternatives. >There is no "ideal" design, since there are so many tradeoffs to be made -- >gain, front/back ratio, bandwidth, size, which you can't maximize all at >once. > > EZNEC doesn't have an optimizer -- if you use EZNEC you have to tweak the > design yourself. People who have used optimizing programs have told me > they've often been able to improve on the "optimized" design by hand > tweaking with EZNEC. > > Roy Lewallen, W7EL > > David wrote: >> Can someone explain to me how a new antenna design is started. Do you >> take an initial standard design and then enter it into a modeling program >> and optimize it for the required parameters ? >> >> Is there a suitable reference book that would explain this process. I am >> thinking about the Cebik antenna modeling book but think this may only >> cover how to model and change an existing design,would it cover how to >> come up with the initial design in the first place ? >> >> Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm >> diameter elements. >> >> Is there a standard formula that would be used to calculate initial >> lengths and distances between elements. Then you enter this design into >> say EZNEC and use the optimizer to tweak the design. >> >> Thanks in advance >> >> Regards >> >> David >> Article: 220986 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Dipoles and the rig's RF ground... Date: Wed, 11 Jan 2006 19:30:13 -0800 Message-ID: References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> <11sbgjhmh57cvae@corp.supernews.com> "Roy Lewallen" wrote in message news:11sbgjhmh57cvae@corp.supernews.com... > I disagree. > > I'd venture to guess that the average output power of a 100 watt PEP > sideband rig is no more than about 10 watts unless heavy compression is > being used. And I think you'll find that a 10 watt resistor inside a > typical tuner cabinet -- representing loss of all the transmitted power -- > will make a barely noticeable difference in the cabinet temperature. Well for heaven's sake of course! Who would use SSB to make a test like this? Put it on CW and put a brick on the key. Come back after dinner. Then you'll know. > > Add to that the fact that the thermal time constant of the tuner is > probably longer than the typical transmitting session, so the power needs > to be averaged over the receiving periods, too. Average, shmaverage. 100% duty cycle during the test. > > If you're running a kW, you're up to 100 watts or so during transmit only. > But can you tell the difference with your "calibrated" hand between 1 dB > loss in the tuner (25 watts), 3 dB loss in the tuner (50 watts), or 100% > of the power lost in the tuner (100 watts)? Between 25, 50 and 100? You betcha, although calibration of hand might have to be checked. Remember, we're not talking NIST here, just an idea of what's happening. > > I'd love to see the results of a double-blind study where a measured tuner > loss is compared with an estimate made using Bill's method. But I think > the chances of that are about the same as finding a double-blind study of > the audio quality enhancement of $1000 speaker cables. Bill's method will be less accurate, more cost effective and good enough. :-) Bill, W6WRT Article: 220987 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Starting point for antenna design Date: Wed, 11 Jan 2006 20:00:16 -0800 Message-ID: <11sbl2ib3gta963@corp.supernews.com> References: <11sbh4k4gvisc1d@corp.supernews.com> <43c5ce5c@kcnews01> Crazy George wrote: > Roy: > > Whatever happened to YO? Was that one of your creations which you stopped > selling? Or was it Beezley's? That was Brian Beezley's program. The last I heard, you can still buy it and his other programs, but only by mail. Look up K6STI in one of the amateur radio databases for his address. Roy Lewallen, W7EL Article: 220988 of rec.radio.amateur.antenna From: Roy Lewallen Subject: Re: Dipoles and the rig's RF ground... Date: Wed, 11 Jan 2006 20:04:00 -0800 Message-ID: <11sbl9i6acv2qf4@corp.supernews.com> References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> <11sbgjhmh57cvae@corp.supernews.com> Bill Turner wrote: > > Well for heaven's sake of course! Who would use SSB to make a test like > this? Put it on CW and put a brick on the key. Come back after dinner. Then > you'll know. > . . . So that's where those unidentified carriers that stay on for hours come from. I'd always wondered. Roy Lewallen, W7EL Article: 220989 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: radar and health ? digressing to keyless remotes... References: <8545c34b738aa8f3099fdd2334602bc0.99986@mygate.mailgate.org> <9AqdnWDnPbDRsFneSa8jmw@karoo.co.uk> Message-ID: Date: Thu, 12 Jan 2006 04:16:26 GMT Gene Fuller wrote: > ..., but pure photon radiation can certainly be "ionizing". My ITT "Reference Data for Radio Engineers" says gamma rays are EM waves which are certainly "ionizing". -- 73, Cecil http://www.qsl.net/w5dxp Article: 220990 of rec.radio.amateur.antenna From: Owen Duffy Subject: Re: Dipoles and the rig's RF ground... Message-ID: References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> <11sbgjhmh57cvae@corp.supernews.com> Date: Thu, 12 Jan 2006 07:17:33 GMT On Wed, 11 Jan 2006 18:44:00 -0800, Roy Lewallen wrote: >I'd venture to guess that the average output power of a 100 watt PEP >sideband rig is no more than about 10 watts unless heavy compression is >being used. And I think you'll find that a 10 watt resistor inside a Roy, I did some experiments a few years back when the FCC OET formed a view that the average power of an SSB voice signal was something like 40% of PEP. My experiment was to modulate a TS440 normally with ALC, with and without compression, and to analyse the audio captured from a comms monitor. The ratios averaged over 30s that I obtained were -13dB and -11dB. Those numbers are consistent with the practice in carrier telephone systems in estimating the power of a n channel multiplex. Later, I have made the same measurements off-air with FSM which reports measurements with an average responding detector, RMS detector, quasi peak detector and peak detector. The results averaged over seconds were -10 to -15dB. I have no idea where OET got -4dB (averaged over 6 minutes). I don't doubt that it is possible to get several dB loss in an ATU, but it says more about the understanding of the person using it in that way than the basis for a law for tuner loss. A chap was telling me on air a few weeks back how good his MFJ tuner was, it could tune anything. He got 1:1 and discovered he didn't even have the aerial connected, how good is that! I suggested he take the covers off and see if the coil support strips had softened / deformed / charred. How could I tell him to stop viewing the world through an SWR meter? Owen -- Article: 220991 of rec.radio.amateur.antenna From: "Reg Edwards" Subject: Re: Dipoles and the rig's RF ground... Date: Thu, 12 Jan 2006 07:34:30 +0000 (UTC) Message-ID: References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> <11sbgjhmh57cvae@corp.supernews.com> "Owen Duffy" wrote - How could I tell him to stop viewing the world through an > SWR meter? ========================================= Easy! Just tell him he has never viewed the world through an SWR meter. He hasn't got one. He has a TLI. ---- Reg. Article: 220992 of rec.radio.amateur.antenna From: "Jerry Martes" References: Subject: Re: Any Such Coax Switch? Message-ID: Date: Thu, 12 Jan 2006 09:27:34 GMT "jimbo" wrote in message news:O9GdnbsyOPa6AVjeRVn-sQ@comcast.com... >I have two, 2 meter radios, one in my basement shack and one in my computer >room on the second floor. I have one 2 meter antenna located in the third >floor attic. I would like a switch that would switch the antenna between >the two radios and I want the radio that is not connected to the antenna to >be connected to a dummy load. > > Maybe I haven't looked hard enough, but all of the switches I have found > so far, switch multiple antennas to one radio and ground the unused > antenna(s). > > Thanks for any help, jimbo Jimbo How much power?? I have built some fairly good coax switches for 144 MHz with microswitches. They wont stand up to a KW. But they sure can work OK at 10 or 20 watts. I'd consider using three spdt coax switches for your application. Jerry Jerry Article: 220993 of rec.radio.amateur.antenna From: "SOMMERGIBILE" Subject: Increase selectivity by a Q multiplier Date: Thu, 12 Jan 2006 10:43:38 +0100 Message-ID: <43c6261b$1$334$5fc30a8@news.tiscali.it> http://web.tiscali.it/am2zy/ Article: 220994 of rec.radio.amateur.antenna From: John Ferrell Subject: Re: Starting point for antenna design Message-ID: <1qncs191l12sktnafsutgk2oh8qnpo6jdb@4ax.com> References: Date: Thu, 12 Jan 2006 14:16:01 GMT There are many parameters to chose in designing an antenna. Beyond the antenna itself are the costs, tolerable size, available materials and available tools. I recently took the ARRL antenna course and purchased Roy's EZNEC+ program. I describe my current level as an "advanced beginner". I once scaled a 4 (5?) element yagi for an antenna measuring event >from the Arrl Handbook to 1296mhz using a piece of plastic tube for a boom and #12 wire for elements. The measured gain and the plot looked pretty much like the book said it would. It fits in a "book-sized" box. My current project is "What can I do with a 20 foot radiator?" Working out the details (the devil is indeed in the details!) sure is a lot easier with EZNEC than it is with physical modeling. There are not many antennas that cannot be evolved from a straight piece of wire. On Thu, 12 Jan 2006 00:39:01 GMT, David wrote: >Can someone explain to me how a new antenna design is started. Do you >take an initial standard design and then enter it into a modeling >program and optimize it for the required parameters ? > >Is there a suitable reference book that would explain this process. I am >thinking about the Cebik antenna modeling book but think this may only >cover how to model and change an existing design,would it cover how to >come up with the initial design in the first place ? > >Example: Say I want to design a 4 Element Yagi at 921 MHz using 6mm >diameter elements. > >Is there a standard formula that would be used to calculate initial >lengths and distances between elements. Then you enter this design into >say EZNEC and use the optimizer to tweak the design. > >Thanks in advance > >Regards > >David > John Ferrell W8CCW Article: 220995 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Starting point for antenna design References: <1qncs191l12sktnafsutgk2oh8qnpo6jdb@4ax.com> Message-ID: Date: Thu, 12 Jan 2006 15:14:32 GMT John Ferrell wrote: > My current project is "What can I do with a 20 foot radiator?" Working > out the details (the devil is indeed in the details!) sure is a lot > easier with EZNEC than it is with physical modeling. Assuming a 20 ft. vertical with 20 ft. radials, how about feeding it with an autotuner, like the SGC-230, and using it for 40m-10m? It will also work at reduced power output on 75m. -- 73, Cecil, http://www.qsl.net/w5dxp Article: 220996 of rec.radio.amateur.antenna Message-ID: <43C67928.5F2C627A@luke.com> From: Luke Subject: Re: Home Made Hazer Ideas? References: <2jlwf.4907$%W1.831@newsread2.news.atl.earthlink.net> Date: Thu, 12 Jan 2006 15:43:38 GMT If he builds it with aluminum and uses the correct grade, should be no problem. Since his tower tapers, he could use larger wheels at the top of the device to keep him plumb at the higher levels. Have you looked into renting a bucket lift, not too expensive for one time and a lot safer ! > > Maybe he doesn't quite know what to look for. > Many years ago an article was published here how to make this Hazer type > device..It looked heavy on the side of his tower. > If anyone wants the article, I could try to find it and make a scan. > Eskay. Article: 220997 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Any experience with the G5RV multiband wire antenna? References: <184c4$43c1dc66$42a1bfc2$11376@FUSE.NET><43C1F19E.533D@wt.net> <1136815006.906927.74130@z14g2000cwz.googlegroups.com> <0Dvwf.49167$BZ5.38064@newssvr13.news.prodigy.com> <1rn8s11ue9botohfvnue2csg670tbqvr1q@4ax.com> Message-ID: <08vxf.156$F_3.73@newssvr29.news.prodigy.net> Date: Thu, 12 Jan 2006 16:06:20 GMT Owen Duffy wrote: > http://www.vk1od.net/temp/G5RV-W5DXP.GIF Owen, what software did you use to generate that graphic? -- TNX & 73, Cecil, http://www.qsl.net/w5dxp Article: 220998 of rec.radio.amateur.antenna From: "Bill Turner" Subject: Re: Dipoles and the rig's RF ground... Date: Thu, 12 Jan 2006 08:15:05 -0800 Message-ID: References: <79c03$43c41226$471d24c1$2218@ALLTEL.NET> <1136927708.070996.198280@f14g2000cwb.googlegroups.com> <1136970581.397887.291800@o13g2000cwo.googlegroups.com> <00tas15me6bpn4801vrkd6cho9hkm2o0b6@4ax.com> <11sbgjhmh57cvae@corp.supernews.com> <11sbl9i6acv2qf4@corp.supernews.com> ORIGINAL MESSAGE: "Roy Lewallen" wrote in message news:11sbl9i6acv2qf4@corp.supernews.com... > So that's where those unidentified carriers that stay on for hours come > from. I'd always wondered. > > Roy Lewallen, W7EL ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Huh-uh. I do some testing on the air, but always at the appropriate times. Ten meters in the wee hours of the morning, 80 meters at high noon, etc. I don't QRM and I do identify. Bill, W6WRT Article: 220999 of rec.radio.amateur.antenna From: Bob Dixon Subject: Re: 8jk Date: Thu, 12 Jan 2006 12:19:26 -0500 Message-ID: References: <1136934974.430378.213490@g14g2000cwa.googlegroups.com> <11sb107cm3i6sa0@corp.supernews.com> There are some other advantages to the 8JK antenna that are not so obvious: 1. You don't need to worry about whether a DX station is coming in via long or short path, since you get them both at once, and the strongest one wins. 2. You can investigate propagation to various parts of world by listening for your own round-the-world echo in various directions. I was a colleague of John Kraus W8JK for many years, and he used to tell me about his round-the-world experiments. I was in his shack once when he did it. Of course you need rapid switching to go from transmit to receive. Typically a single dit is used. Bob W8ERD Article: 221000 of rec.radio.amateur.antenna From: Bob Bob Subject: Re: Questions about antennas for 2.4 Ghz References: <1137089669.757781.233540@g44g2000cwa.googlegroups.com> Message-ID: Date: Thu, 12 Jan 2006 14:00:54 -0600 Hi Johann There is no doubt a lot of info on internet articles you could wade. through. Since you have a practical requirement though I'll try and answer. The length and diameter of an antenna is related to the frequency. In rough terms a half wave in free space on 2.4GHz is calculated as 300/2400MHz/2 metres or about 60mm. A half wave dipole antenna tends to be shorter than this by a percentage between about 85% and 98%. The variation being a function of the material diameter vs its length (ie the fatter the antenna element the shorter its length) If you etch the design into a PCB the dielectric around it (PCB insulative material) will lower that percentage more. I don't know how much off hand. Within limits however you can match any transmitter to any simple antenna length. Small variations and errors in length (say 20%) wont deter very much from the performance provided you have done a good job coupling the transmitter to it. If however you use a simple element of more than a half wavelength you can get an undesirable pattern of radiation from it. Gain antennas like yagi's will suffer badly from this much variation though. Coupling/tuning in this sense means getting a maximum power transfer >from the transmitter to the antenna. Antennas for longer distances on 2.4GHz are almost always devices built for gain. They can use a cluster of dipoles phased to concentrate the radiation into a narrower pattern, hence the received signal at the other end is stronger than from a simple dipole. The downside is of course if either end is moving/rotating in respect to the other. Loss of signal results. (Think of a searchlight) Yes etching an antenna on a PCB is a good way to do it. "Patch antennas" might be the term to look for, as well as "slot antennas" with PCB as part of the search criteria. One of the conditions you didn't specify is whether the ends of the link are fixed or moving. If they are fixed you can get away with lower power and gain antennas. If they are moving you probably want an antenna that radiates equally in all directions. This is actually difficult to do as there is always variation in different angles from the antenna. A dipole for instance radiates best at 90 degrees to the element. There is however virtually no radiation directly off the ends. This doesn't make the system unusable though. Some of the signal will get through via reflection off other objects and a very useful amount will come off at (say) 10% from off the ends. If you have enough power margin it will still work. It will be something like (say) 5m range at almost any attitude and 50m range if you hold the antenna just right! Smallest antenna? A slot would be maybe 60mm long and 20mm wide if etched to a PCB. A quad type element etched on a PCB may me 30mm x 30mm. You could also make a 1/4 wave groundplane. That's a 30mm or so wire perpendicular to a ground plane area (eg PCB) a minimum of 60mm diameter. If you can suffer some efficiency loss you can etch a loaded dipole pattern on a PCB maybe 15 x 10mm but it would be a good idea to test whether the distance loss will be okay in your environment. If you hand make the antenna the coax etc attachment becomes a large lumped reactance/resistive load that has to be allowed for when adjusting for best coupling. Likewise a etched PCB antenna will be affected by components mounted on the reverse side as well as the (say) plastic etc box it is mounted in. The rule is to tune it with everything attached. For the purists out there I have watered this down some and tried to keep heavy theory out of it. I hope however you'll still find it useful. Cheers Bob W5/VK2YQA johannblake@yahoo.com wrote: > > What I need is the smallest antenna possible! > > Thank you for your insight. > Johann Blake > Article: 221001 of rec.radio.amateur.antenna From: "void * clvrmnky()" Subject: Re: Brain Teaser References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> Message-ID: Date: Thu, 12 Jan 2006 18:00:54 -0500 On 12/01/2006 2:09 PM, Cecil Moore wrote: > Problem: > There's a rather strange antenna with two straight wire elements. > The two elements are supported by two non-conductive poles, Pole > A and Pole B of unequal lengths. The bottoms of the poles are at > ground level and the ground is flat. > > One straight 10 foot wire runs directly from the bottom of Pole > A to the top of Pole B. One straight 20 foot wire runs directly > from the bottom of Pole B to the top of Pole A. The feedpoint of > this strange antenna is where the wires intersect and that point > is exactly five feet above the ground. (The two wires form a > non-symetrical 'X' between the poles and the center of the 'X' > is exactly five feet above the ground.) > > Question: What are the heights of Pole A and Pole B, and > how far apart are the two poles? > > Pole A > |\ > | \ > | \ Pole B > | \ | > | \ / | > | /\ | > | / \ | > |/ \| > -+--------+- > <--d---> > Curse you! I'm pretty sure this can be solved with just basic trig, but I've forgotten it all. Law of sines the key? Article: 221002 of rec.radio.amateur.antenna From: "Ralph Mowery" References: <1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com> Subject: Re: Brain Teaser Message-ID: Date: Thu, 12 Jan 2006 23:59:26 GMT "Cecil Moore" wrote in message news:1Qxxf.8331$dW3.1056@newssvr21.news.prodigy.com... > Problem: > There's a rather strange antenna with two straight wire elements. > The two elements are supported by two non-conductive poles, Pole > A and Pole B of unequal lengths. The bottoms of the poles are at > ground level and the ground is flat. > > One straight 10 foot wire runs directly from the bottom of Pole > A to the top of Pole B. One straight 20 foot wire runs directly > from the bottom of Pole B to the top of Pole A. The feedpoint of > this strange antenna is where the wires intersect and that point > is exactly five feet above the ground. (The two wires form a > non-symetrical 'X' between the poles and the center of the 'X' > is exactly five feet above the ground.) > > Question: What are the heights of Pole A and Pole B, and > how far apart are the two poles? > > Pole A > |\ > | \ > | \ Pole B > | \ | > | \ / | > | /\ | > | / \ | > |/ \| > -+--------+- > <--d---> > > P.S. None of my math students can solve this problem. > -- > 73, Cecil, http://www.qsl.net/w5dxp Don't remember where I saw it (about 30 years ago), but there was a parallel resistor problem that was solved similar to this.