125' EFHWA (was: long wire balan)
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I have recieved an overwhelming amount of info on antennas that may take few
days to read through. There is some work to be done on my ground system as well. A little progress was made by adding one radial, which made my TT 253 happy on 20m. The K2 and TT tuner are indicating consistent forward power 10m - 80m and low SWR. I would like to maximize the efficiency of this antenna for multi band use. I am on a 60 x 160 lot, in Dallas, with the shack located in the back corner with a large tree in the front and back that are 100' apart with the 125' EFHWA strung between. Our antenna height is restricted to 35'. Utility lines are locted in the alley along the back. I have a 17m moxon mounted to the roof of the house which is in the middle of the lot. I can change the length, grounding, or add radials along the property edge, but the height is restricted. Thanks, John K5XTX _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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Perfect lot for a G5RV. My lot is about the same with tree's in the front and back. Mine is hung between a front tree and a back tree. Power lines are in the front only a few feet from the end of my G5RV No problem with it. It's up 30 ft and works great in all directions tunes all bands with the K-2 tuner. Seems to work both long and short distance. It's 102 ft long. Easy to make but mine is from antennasmore. Has survived multiple wind storms 60 MPH winds.
Jay KC9EUH FP 750 FISTS 5344 John Rader <[hidden email]> wrote: I have recieved an overwhelming amount of info on antennas that may take few days to read through. There is some work to be done on my ground system as well. A little progress was made by adding one radial, which made my TT 253 happy on 20m. The K2 and TT tuner are indicating consistent forward power 10m - 80m and low SWR. I would like to maximize the efficiency of this antenna for multi band use. I am on a 60 x 160 lot, in Dallas, with the shack located in the back corner with a large tree in the front and back that are 100' apart with the 125' EFHWA strung between. Our antenna height is restricted to 35'. Utility lines are locted in the alley along the back. I have a 17m moxon mounted to the roof of the house which is in the middle of the lot. I can change the length, grounding, or add radials along the property edge, but the height is restricted. Thanks, John K5XTX _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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In reply to this post by John Rader
On Mon, 02 Aug 2004 20:46:17 -0500, John Rader wrote:
>125' EFHWA strung between. These abbreviations drive me nuts! What the hell is an EFHWA? Jim K9YC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by John Rader
Thats easy Jim, its in Slobodian and means a dipole.
Or you can make up your own definition. The last three could be Horizontal Wire Antenna. You fill in the gaps yourself for E and F. Likewise the sentiments on strange abreviations. Bob, G3VVT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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In reply to this post by Jim Brown-10
> These abbreviations drive me nuts!
Me too sometimes ;-) EFHWA - End Fed Half Wave Antenna - Some examples found on the web: http://www.qsl.net/aa5tb/efha.html http://www.qsl.net/aa5tb/halfwave.html http://www.g3ycc.karoo.net/endfed2.html http://www.qsl.net/aa5tb/coupler.html http://www.g3ycc.karoo.net/endfed.htm This is my choice for portable work where I have 1 support...performs quite well... 73's Trev - K6ESE http://www.qsl.net/k6ese dit dididit dit dit dit _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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A commercial version, very nicely made, in my opinion, is made by Par
Electronics and sold by Universal Radio. It's got a sealed coupling network with a SO239 and the actual antenna wire is replaceable. 73, doug From: "Trev - K6ESE" <[hidden email]> Date: Tue, 3 Aug 2004 13:49:28 -0700 > These abbreviations drive me nuts! Me too sometimes ;-) EFHWA - End Fed Half Wave Antenna - Some examples found on the web: http://www.qsl.net/aa5tb/efha.html http://www.qsl.net/aa5tb/halfwave.html http://www.g3ycc.karoo.net/endfed2.html http://www.qsl.net/aa5tb/coupler.html http://www.g3ycc.karoo.net/endfed.htm This is my choice for portable work where I have 1 support...performs quite well... 73's Trev - K6ESE http://www.qsl.net/k6ese dit dididit dit dit dit _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 125' EFHWA (was: long wire balan)
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In reply to this post by Trev - K6ESE
At least it's not another TLA ........ (Three-letter Acronym) :-)
I work in aerospace, a field rife with with TLA's. 73, Dean K0MKT K2 #4359 (finishing alignments tonite, then on-the-air!) -----Original Message----- From: [hidden email] [mailto:[hidden email]]On Behalf Of Trev - K6ESE Sent: Tuesday, August 03, 2004 2:49 PM To: Jim Brown; Elecraft List Subject: Re: [Elecraft] 125' EFHWA (was: long wire balan) > These abbreviations drive me nuts! Me too sometimes ;-) EFHWA - End Fed Half Wave Antenna - Some examples found on the web: _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 125' EFHWA (was: long wire balan)
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In reply to this post by Trev - K6ESE
I think it must have been self defense by someone. Some time back I gave up
using the term "dipole" because the current crop of Hams seems to think that means a center fed antenna of some arbitrary length, rather than an antenna that is exactly 1/2 wave long and which might be fed anywhere. So I gave up and started saying that I had a half wave antenna fed at the center, or at the end or off-center, etc. But, since I like others to understand what I'm saying, I avoid acronyms. I take it the coupler at: http://www.qsl.net/aa5tb/coupler.html Is for QRP only! At 50 watts or so, I used to get flash-over in a wide spaced air variable in that circuit. I used a large "Air Dux" coil with it. The voltages present at the end of a dipole are huge at any significant power level. I can't imagine the wire insulation on a toroid or a poly cap withstanding more than a few watts of RF there. Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Trev - K6ESE > These abbreviations drive me nuts! Me too sometimes ;-) EFHWA - End Fed Half Wave Antenna - Some examples found on the web: http://www.qsl.net/aa5tb/efha.html http://www.qsl.net/aa5tb/halfwave.html http://www.g3ycc.karoo.net/endfed2.html http://www.qsl.net/aa5tb/coupler.html http://www.g3ycc.karoo.net/endfed.htm This is my choice for portable work where I have 1 support...performs quite well... 73's Trev - K6ESE http://www.qsl.net/k6ese dit dididit dit dit dit _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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In reply to this post by John Rader
Mediocre? I'll match it against any trap dipole. If I didn't have the G5RV I would suggest a windom. Had a trap dipole once and long wire beat it G5 RV beat the long wire. I have read varying reports on the G5RV some call it compromise others love it. I would say it's the best antenna I have had. Unless you have alot of real estate and money. And can put up Rhombics and huge beams up 50 ft or more. I guess since the G5RV works on all bands except 160m unless you have a good ground or double the length mine must be a mistake. So many different antenna's for a small lot.
Jay KC9EUH FP 750 FISTS 5344 Jim Brown <[hidden email]> wrote: >Perfect lot for a G5RV. But a mediocre antenna. Assuming 80, 40, 30, 20, 15, and 10 are your most important bands, I suggest an 80/40 trap dipole using loading coil traps made by Barry at HyPower Antenna Co (or buy the entire dipole pre-made). Add a DX Engineering balun, and it will work very well on 80, 40, and 30. I've got two of his antennas up now, and just bought three more sets of 160 m loading coil traps for my vacation QTH. Add a parallel wire 20 meter element and you've got that band covered. Spacers can be easily built using UV-resistant 1/2" PVC conduit. Barry also sells an antenna like that pre-made. For the higher bands, build a parallel wire dipole using the same parts -- a DX Engineering balun, #12 or #14 THHN wire from Home Depot, and the spacers. That shorter antenna will be much easier to find a home for, and doesn't need to be as high. I've become a big fan of parallel wire (fan) dipoles after having built some for my vacation QTH, Field Day, and now for the home QTH. Easy to build and no traps. That means higher efficiency and greater bandwidth. I use the traps only when I don't have the space for a full size dipole. Jim Brown K9YC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Ron D'Eau Claire-2
For a single band, there is an interesting old-time alternative called
a single wire Windom. It is a horizontal halfwave with a single wire feedline connected to the horizontal wire off-center. For 20 the "dipole" part is 34 feet. The single wire feed is soldered to the horizontal at a point 12.5 feet from either end and drops to the ground. The wire is fed against ground. The single wire exhibits a 400-450 ohm feed against ground, regardless of the height of the height of the horizontal under 3/4 wavelength. The vertical part radiates very little. A poor ground that would ruin a vertical's performance at 20-35 ohms feed Z will do OK at 400-450 feed Z. As in a single 17' radial wire just laid on the ground. You can feed it with a unun wound on a toroid with a 3:1 turns ratio. SWR on the low Z side easily matches 50 ohms well enough for coax or any antenna tuner, without having to endure the high voltages found on an endfed halfwave. It has the predictable performance of a good dipole, without the center insulator, and without the weight of a coax feed. If you use something like flex-weave for all the wires it can be wound up and carried around. 73, Guy. ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> I think it must have been self defense by someone. Some time back I gave up using the term "dipole" because the current crop of Hams seems to think that means a center fed antenna of some arbitrary length, rather than an antenna that is exactly 1/2 wave long and which might be fed anywhere. So I gave up and started saying that I had a half wave antenna fed at the center, or at the end or off-center, etc. But, since I like others to understand what I'm saying, I avoid acronyms. I take it the coupler at: http://www.qsl.net/aa5tb/coupler.html Is for QRP only! At 50 watts or so, I used to get flash-over in a wide spaced air variable in that circuit. I used a large "Air Dux" coil with it. The voltages present at the end of a dipole are huge at any significant power level. I can't imagine the wire insulation on a toroid or a poly cap withstanding more than a few watts of RF there. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Another "dipole" with a simpler tuner and feedline
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You just described the antenna I take camping with me and my K2. I have
an ATU on the original top so it works nicely. The flex weave makes it very nice for throwing up and taking down. I can tie knots in the wire and they come out fine. I tie a sheet bend to some mason's line and take a few 2 ounce sinkers to whip them up in the fir trees. Or if I feel brave I swing the lead weight around my head and let fly. Normally I can get it right where I want with that method. Occasionally I have to duck rather abruptly. Your mileage may vary :) I designed the Windom to work on 80 meters so it takes a bit of string and two trees a bit further apart than your 20 meter version. But in Oregon we have plenty of trees (outside of the clearcuts). {Earth first; we'll log the other planets later :) 73, Kevin. KD5ONS On Tue, 3 Aug 2004 21:47:01 -0400, Guy Olinger, K2AV <[hidden email]> wrote: > For a single band, there is an interesting old-time alternative called > a single wire Windom. It is a horizontal halfwave with a single wire > feedline connected to the horizontal wire off-center. For 20 the > "dipole" part is 34 feet. The single wire feed is soldered to the > horizontal at a point 12.5 feet from either end and drops to the > ground. > > The wire is fed against ground. The single wire exhibits a 400-450 ohm > feed against ground, regardless of the height of the height of the > horizontal under 3/4 wavelength. The vertical part radiates very > little. A poor ground that would ruin a vertical's performance at > 20-35 ohms feed Z will do OK at 400-450 feed Z. As in a single 17' > radial wire just laid on the ground. > > You can feed it with a unun wound on a toroid with a 3:1 turns ratio. > SWR on the low Z side easily matches 50 ohms well enough for coax or > any antenna tuner, without having to endure the high voltages found on > an endfed halfwave. > > It has the predictable performance of a good dipole, without the > center insulator, and without the weight of a coax feed. If you use > something like flex-weave for all the wires it can be wound up and > carried around. > > 73, Guy. > > > ----- Original Message ----- > From: "Ron D'Eau Claire" <[hidden email]> > > > I think it must have been self defense by someone. Some time back I > gave up > using the term "dipole" because the current crop of Hams seems to > think that > means a center fed antenna of some arbitrary length, rather than an > antenna > that is exactly 1/2 wave long and which might be fed anywhere. > > So I gave up and started saying that I had a half wave antenna fed at > the > center, or at the end or off-center, etc. > > But, since I like others to understand what I'm saying, I avoid > acronyms. > > I take it the coupler at: > http://www.qsl.net/aa5tb/coupler.html > > Is for QRP only! At 50 watts or so, I used to get flash-over in a wide > spaced air variable in that circuit. I used a large "Air Dux" coil > with it. > The voltages present at the end of a dipole are huge at any > significant > power level. I can't imagine the wire insulation on a toroid or a poly > cap > withstanding more than a few watts of RF there. > > Ron AC7AC > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com -- _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Another "dipole" with a simpler tuner and feedline
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The "windom" has been a popular and effective antenna that turns up
regularly since I got my first ticket over half a century ago. Originally it was an alternative to using heavy, open wire feedline for a horizontal dipole. The idea was that the single wire "feeder" would attach at the point on the dipole that matched the characteristic impedance of the wire, so there'd be no standing waves on the "feed" wire. No standing waves = no radiation; exactly what we want in a feedline. There's a lot in the Ham literature about how to find that magic feedpoint exactly, using RF ammeters connected to the horizontal wire and moving the feed point back and forth with pulleys, etc., before attaching it permanently. Unfortunately, that only works at ONE frequency! Most Hams like to QSY a bit, even back in the days of crystal control! But what does work FB is simply loading the "Windom" up as a random wire like Kevin does. The vertical "feedline" now radiates like crazy with the top wire acting as "top loading" to make the vertical wire electrically longer than it appears. That raises the feed point impedance, and so the efficiency, on the lower bands. Since the "feeder" doesn't connect at the center, the top wire radiates a lot too. The end result is a big mix of horizontal and vertical radiation. So the "Windom" has become a popular and effective multi-band antenna, even though Windom himself designed it for single-frequency use. Just goes to show the true spirit of Hams - try it and see if it works. If it works use it! Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Kevin Rock Sent: Tuesday, August 03, 2004 7:27 PM To: [hidden email] Subject: Re: [Elecraft] Another "dipole" with a simpler tuner and feedline You just described the antenna I take camping with me and my K2. I have an ATU on the original top so it works nicely. The flex weave makes it very nice for throwing up and taking down. I can tie knots in the wire and they come out fine. I tie a sheet bend to some mason's line and take a few 2 ounce sinkers to whip them up in the fir trees. Or if I feel brave I swing the lead weight around my head and let fly. ... 73, Kevin. KD5ONS _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Another "dipole" with a simpler tuner and feedline
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In reply to this post by Guy, K2AV
Inverted L for 20:
Have your horizontal lamda/2 wire fed at the other end. Make the vertical feeding wire (single) the same length. Voltage feed it on 20 and 40 meters with tuned circuit. Current feed on 80 meters against 20 meter radial. Horizontal wire on 10 meters height is at least 6 dB better for 20m band than any simple vertical. But this antenna has some vertical radiation,too. For 40 the radiation pattern is suprising good for domestic QSO and low enough for some DX, too. For 80 this is but a shortened top-loaded vertical with poor number of radials, but it works. Benny OH9NB On Tue, 3 Aug 2004 21:47:01 -0400, Guy Olinger, K2AV <[hidden email]> wrote: > For a single band, there is an interesting old-time alternative called > a single wire Windom. It is a horizontal halfwave with a single wire > feedline connected to the horizontal wire off-center. For 20 the > "dipole" part is 34 feet. The single wire feed is soldered to the > horizontal at a point 12.5 feet from either end and drops to the > ground. > > The wire is fed against ground. The single wire exhibits a 400-450 ohm > feed against ground, regardless of the height of the height of the > horizontal under 3/4 wavelength. The vertical part radiates very > little. A poor ground that would ruin a vertical's performance at > 20-35 ohms feed Z will do OK at 400-450 feed Z. As in a single 17' > radial wire just laid on the ground. > > You can feed it with a unun wound on a toroid with a 3:1 turns ratio. > SWR on the low Z side easily matches 50 ohms well enough for coax or > any antenna tuner, without having to endure the high voltages found on > an endfed halfwave. > > It has the predictable performance of a good dipole, without the > center insulator, and without the weight of a coax feed. If you use > something like flex-weave for all the wires it can be wound up and > carried around. > > 73, Guy. > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com -- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/ _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by John Rader
In a message dated 8/3/04 8:25:23 PM Eastern Daylight Time,
[hidden email] writes: > Mediocre? I'll match it against any trap dipole. If I didn't have the > G5RV I would suggest a windom. Had a trap dipole once and long wire beat it G5 > RV beat the long wire. I have read varying reports on the G5RV some call it > compromise others love it. I would say it's the best antenna I have had. My results have been that a *good* trap dipole beats a G5RV - but not by much. Both beat an equivalent long wire *unless* the long wire has a good ground system (as in more than a few radials and a ground stake). YMMV The keys to trap dipoles are the trap construction and overall adjustment. Lossy, low Q traps will give mediocre results. Good high Q traps will do much better - typically less than 1 dB down from a full size dipole. 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 125' EFHWA (was: long wire balan)
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A simple ground stake or single wire counterpoise can be expected to produce
antenna efficiencies of over 90% when used with an end fed *half wave* wire. The ground resistance is in series with the radiation resistance. A half wave shows several thousands of ohms at the end while even a crummy ground rod usually will show a few hundred ohms. So almost all the RF is dissipated in the radiation resistance of the antenna and only a small percentage is dissipated in the ground connection resistance. Where that scenario breaks down is when the antenna is shorter. At 1/4 wavelength it has a radiation resistance of about 35 ohms. Now more than 90% of the RF is lost in a 300+ ohm ground connection and less than 10% is radiated. At lengths less than 1/4 wavelength the situation worsens. It's not uncommon for a short whip and single wire ground counterpoise to have an efficiency of only 1 or 2 percent. The problem with 1/2 wave wires is that most antenna tuners, including the various tuners offered by Elecraft, can't match to them. The high impedance that makes them efficient is too high for the ATU to handle. So when using most ATU's a compromise length is needed that is as close to 1/2 wavelength, or a multiple of 1/2 wavelength, but still within range of the ATU. The efficiency will still be good. Ron AC7AC -----Original Message----- ) In a message dated 8/3/04 8:25:23 PM Eastern Daylight Time, [hidden email] writes: > Mediocre? I'll match it against any trap dipole. If I didn't have > the > G5RV I would suggest a windom. Had a trap dipole once and long wire beat it G5 > RV beat the long wire. I have read varying reports on the G5RV some call it > compromise others love it. I would say it's the best antenna I have had. My results have been that a *good* trap dipole beats a G5RV - but not by much. Both beat an equivalent long wire *unless* the long wire has a good ground system (as in more than a few radials and a ground stake). YMMV The keys to trap dipoles are the trap construction and overall adjustment. Lossy, low Q traps will give mediocre results. Good high Q traps will do much better - typically less than 1 dB down from a full size dipole. 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 125' EFHWA (was: long wire balan)
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In reply to this post by John Rader
Absolutely, for QRP levels!
With the high impedances come very high RF voltages - voltages in the hundreds, even thousands of volts. That's why compact ATU's like the Elecraft ATU's can't handle those impedances - even if they could affect a match the voltages would destroy the caps, relays and other components at any power above a few watts. There's a reason why the antenna tuners shown in the old textbooks have huge capacitors and big coils wound on ceramic forms or air-wound and everything mounted on big ceramic stand-off insulators! That's what is needed when running more than a couple of watts into a really high-impedance load. Even at 50 watts I've seen a transmitting variable capacitor with 1/4-inch (6mm) plate spacing arc over when coupling to a really high-impedance load. Ron AC7AC -----Original Message----- Or..... an intermediate simple ATU such as http://www.qrpproject.de/UK/fuchs_ant_.htm This should work? 73, Deni F5VJC GM3SKN _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: 125' EFHWA (was: long wire balan)
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In reply to this post by dean mertz
Well, it *is* an ETLA (extended three-letter acrynym), which is
something I had to deal with a lot at Intel -- they love TLAs and ETLAs like only aerospace folks would understand. oo72 de Trent - N7GMT ----- Original Message ----- From: "Dean Mertz" <[hidden email]> To: <[hidden email]> Sent: Tuesday, August 03, 2004 15:58 Subject: RE: [Elecraft] 125' EFHWA (was: long wire balan) At least it's not another TLA ........ (Three-letter Acronym) :-) I work in aerospace, a field rife with with TLA's. 73, Dean K0MKT K2 #4359 (finishing alignments tonite, then on-the-air!) -----Original Message----- From: [hidden email] [mailto:[hidden email]]On Behalf Of Trev - K6ESE Sent: Tuesday, August 03, 2004 2:49 PM To: Jim Brown; Elecraft List Subject: Re: [Elecraft] 125' EFHWA (was: long wire balan) > These abbreviations drive me nuts! Me too sometimes ;-) EFHWA - End Fed Half Wave Antenna - Some examples found on the web: _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: 125' EFHWA (was: long wire balan)
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In reply to this post by Ron D'Eau Claire-2
I agree your findings may be true. Really depends on what you want the antenna's to do. On 20 meters I would have to say that you would have to have a very good dipole to match the G5RV since that is what a G5RV really is. I don't notice any directivity at all with my G5RV on 40 and 80 or 30 meters. I did with a dipole. Also at about the same height with the long wire I didn't think my home state had any hams. Now they do. May have something to do with the surroundings but doesn't seem to have directivity on any of the bands. The long wire I had 100 ft of wire and single wire counterpoise. Tried grasswire and varying heights. Checked against the G5RV at 10' and then 31'. The Dipole I didn't like and stayed with long wire was a Barker and Williamson.
The last place I lived I couldn't have an antenna. I made a loop around my carport it worked pretty good. But can't compare it to anything. I was just posting a suggestion for someone in the same circumstances I have. Except on 20 meters full size monoband dipoles may be best but I know my neighbors and Wife wouldn't like all that wire in such a small place. I talk to the same people every week and can switch back and forth between antenna's or could I have since taken the long wire down. And no I don't sell antenna's as one person seemed to think. May have something to do with where I live also. Possible the radiation pattern of my antenna is good for 470' above sea level. Who really knows it's all theory and each situation is different. What works at one place may not work at yours. After all unless you live out in an open field and get your antenna above 50 ft will it really perform as the software says? Ron D'Eau Claire <[hidden email]> wrote: A simple ground stake or single wire counterpoise can be expected to produce antenna efficiencies of over 90% when used with an end fed *half wave* wire. The ground resistance is in series with the radiation resistance. A half wave shows several thousands of ohms at the end while even a crummy ground rod usually will show a few hundred ohms. So almost all the RF is dissipated in the radiation resistance of the antenna and only a small percentage is dissipated in the ground connection resistance. Where that scenario breaks down is when the antenna is shorter. At 1/4 wavelength it has a radiation resistance of about 35 ohms. Now more than 90% of the RF is lost in a 300+ ohm ground connection and less than 10% is radiated. At lengths less than 1/4 wavelength the situation worsens. It's not uncommon for a short whip and single wire ground counterpoise to have an efficiency of only 1 or 2 percent. The problem with 1/2 wave wires is that most antenna tuners, including the various tuners offered by Elecraft, can't match to them. The high impedance that makes them efficient is too high for the ATU to handle. So when using most ATU's a compromise length is needed that is as close to 1/2 wavelength, or a multiple of 1/2 wavelength, but still within range of the ATU. The efficiency will still be good. Ron AC7AC -----Original Message----- ) In a message dated 8/3/04 8:25:23 PM Eastern Daylight Time, [hidden email] writes: > Mediocre? I'll match it against any trap dipole. If I didn't have > the > G5RV I would suggest a windom. Had a trap dipole once and long wire beat it G5 > RV beat the long wire. I have read varying reports on the G5RV some call it > compromise others love it. I would say it's the best antenna I have had. My results have been that a *good* trap dipole beats a G5RV - but not by much. Both beat an equivalent long wire *unless* the long wire has a good ground system (as in more than a few radials and a ground stake). YMMV The keys to trap dipoles are the trap construction and overall adjustment. Lossy, low Q traps will give mediocre results. Good high Q traps will do much better - typically less than 1 dB down from a full size dipole. 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: Another "dipole" with a simpler tuner and feedline
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In reply to this post by Ron D'Eau Claire-2
Will probably be the next antenna for me. I would like more info on how to build one like yours Kevin?
Ron D'Eau Claire <[hidden email]> wrote:The "windom" has been a popular and effective antenna that turns up regularly since I got my first ticket over half a century ago. Originally it was an alternative to using heavy, open wire feedline for a horizontal dipole. The idea was that the single wire "feeder" would attach at the point on the dipole that matched the characteristic impedance of the wire, so there'd be no standing waves on the "feed" wire. No standing waves = no radiation; exactly what we want in a feedline. There's a lot in the Ham literature about how to find that magic feedpoint exactly, using RF ammeters connected to the horizontal wire and moving the feed point back and forth with pulleys, etc., before attaching it permanently. Unfortunately, that only works at ONE frequency! Most Hams like to QSY a bit, even back in the days of crystal control! But what does work FB is simply loading the "Windom" up as a random wire like Kevin does. The vertical "feedline" now radiates like crazy with the top wire acting as "top loading" to make the vertical wire electrically longer than it appears. That raises the feed point impedance, and so the efficiency, on the lower bands. Since the "feeder" doesn't connect at the center, the top wire radiates a lot too. The end result is a big mix of horizontal and vertical radiation. So the "Windom" has become a popular and effective multi-band antenna, even though Windom himself designed it for single-frequency use. Just goes to show the true spirit of Hams - try it and see if it works. If it works use it! Ron AC7AC -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Kevin Rock Sent: Tuesday, August 03, 2004 7:27 PM To: [hidden email] Subject: Re: [Elecraft] Another "dipole" with a simpler tuner and feedline You just described the antenna I take camping with me and my K2. I have an ATU on the original top so it works nicely. The flex weave makes it very nice for throwing up and taking down. I can tie knots in the wire and they come out fine. I tie a sheet bend to some mason's line and take a few 2 ounce sinkers to whip them up in the fir trees. Or if I feel brave I swing the lead weight around my head and let fly. ... 73, Kevin. KD5ONS _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Ron D'Eau Claire-2
Modeling and experimentation verify that the 20 meter version has only
MINOR radiation from the vertical portion over the entire band, and using a 50 to 450 ohm (3:1 turns ratio) unun gives an SWR of 1.3:1 or less over the entire 20 meter band. The pattern of radiation shown on EZNEC is essentially a dipole's pattern for the same height and ground from one end of the band to the other. The differences are seen at angles and directions of NULLS for a dipole. As you move away from the Windom's center frequency, these nulls become less pronounced from the increasing miscellaneous radiation from the vertical. In the good ole days they didn't have EZNEC and GHz PC's to COMPUTE or EXPERIMENT with the design. My ancient notes from the 50's for this antenna were substantially off. They used dipole lengths and 44% tap. The horizontal needs to be slightly longer at the lowish heights typically used by QRPers hanging stuff in trees on walkabouts. So we wind up with 34' and 36% tap. Turns out there is a lot of hay to be made revisiting the old-time designs with the snazzy new tools. IF one can actually find the zero vertical radiation point on a Windom, then the width where the vertical radiation is down 30 db from main probably IS very narrow, but practically speaking, the thing is a dipole over the entire twenty meter band. What is neat is to wind the entire thing up on a small spool and throw it in the suitcase along with the K2. And a sharp op with that antenna and a K2 can whup a lid with a beam and a KW any day, from one end of the band to the other. 73, Guy. ----- Original Message ----- From: "Ron D'Eau Claire" <[hidden email]> > > Unfortunately, that only works at ONE frequency! Most Hams like to QSY a > bit, even back in the days of crystal control! _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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