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$wq.9439@bignews7.bellsouth.net> <0bj2r15i9iic4td11aejgpe330g8b07efe@4ax.com> Date: Sat, 07 Jan 2006 07:10:30 GMT On Sat, 07 Jan 2006 00:44:41 +0100, Paul Burridge wrote: >On Tue, 27 Dec 2005 19:00:57 GMT, "kd5sak" >wrote: > > >>Guess that's right, let's see now. Formula ! car wheels just have one big >>lug nut, don't they? >> > >Pit-stop time is critical. You want to race a car that takes 6 guys >all fumbling in over- intimate proximity to change each wheel? NASCAR crews seem to do just fine with on man at each wheel. Each wheel has five lug nuts. R Article: 220856 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: Transmission line help References: <1136601460.068728.122510@g49g2000cwa.googlegroups.com> Message-ID: Date: Sat, 07 Jan 2006 14:24:27 GMT moatesim@gmail.com wrote: > I am self studying transmission lines and I can't figure out this > problem. Given Z(r), Z_not, and 'd' you are asked to find Tau(d). To my > understanding, Tau(d) is 1+ Z_r(normalized with Z_not) divided by (1 - > Z_r(normalized by Z_not)). For the data I had, I don't get the phase of > Tau(d) correct. I would really appreciate if you could point out where > I am making the mistake or explain it to me the correct way to > calculate Tau(d). Different texts use different subscripts. Is Z(r) the load impedance and Z_not the characteristic impedance? What is 'd'? Are you using a Z-parameter analysis? From "Fields and Waves in Communication Electronics", by Ramo, Whinnery, and Van Duzer, page 28: rho = (ZL-Z0)/(ZL+Z0) = Vref/Vfor tau = 2*ZL/(ZL+Z0) = (Vfor+Vref)/Vfor where rho is the voltage reflection coefficient and tau is the voltage transmission coefficient. ZL is the load impedance and Z0 is the characteristic impedance of the transmission line. -- 73, Cecil http://www.qsl.net/w5dxp Article: 220857 of rec.radio.amateur.antenna From: Cecil Moore Subject: Re: MFJ974H References: <1136540435.263601.115880@o13g2000cwo.googlegroups.com> Message-ID: <%GQvf.9894$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... > moatesim@gmail.com 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