1/2 Wave End-Fed Inverted V
from
Joe Everhart, N2CX
on
November 25, 2004
Website:
http://www.njqrp.org/n2cxantennas/halfer/
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I have been experimenting with a half wave end-fed inverted V for a few weeks now. The wire is 62 feet on both legs and connected at the apex. I tune the antenna with the Icom AH-4 remote tuner. I am very happy with the improved reception and forward gain over my 1/4 end fed sloper.
One added bonus is I am now able to work 160 meters. I have 3-counterpoise wires fanned out that are 65 feet in length. I tried 4 counterpoise wires but that seemed to weaken the output signal. Of course the fact that the lower angle of radiation provides better DX listening is a real treat.
I have copied VR2MY in Hong Kong from VE7 land in BC Canada. I would recommend the antenna to anyone that can tune a single wire antenna and who is restricted to supporting the antenna from a single tree. Each leg starts at the peak of my roof (16 feet) and runs to the apex of the antenna. I was able to shoot a weight up and over a branch of the tree using a slingshot. Make sure you leave some slack or use a bundgie cord to take the shock or pull when the tree sways in the wind. There are many great articles on the Internet describing the different configurations of a 1/2-wave end fed antenna.
73, VE7HJ
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1/2 Wave End-Fed Inverted V
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by N8BOA on November 25, 2004
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Sounds like you got it together thats a great idea. Be carefull endfed 1/2 wave antennas have the High Voltage at the ends, right at you antenna tunner. The AH-4 manual (you got to use alot of imagination to call it a manual) also warns of feeding a 1/2 wave antenna. But if your getting away with it go for it. You could try to go a little longer to move the high voltage up the wire. I willbe building a end fed long wire 130ft sloper down to the lake as soon as it frozen
Thanks for the post
P.Sean Coady
N8BOA
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RE: 1/2 Wave End-Fed Inverted V
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by K0BG on November 25, 2004
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The only thing you have to be careful about is the length. If it is a TRUE 1/2 wave antenna, the AH-4 will not tune it. The max range on the AH-4 is 5,000 ohms or about one half what you would expect to see on a true 1/2 wave.
Incidentally, the AH-4 uses a fixed amount of output capacitance for loads over 2,500 ohms or so. This causes the SWR to go up on higher impedance loads. For example, if you were to put a 5,000 ohm resistive load on the output, you'd see an SWR on the input of nearly 3:1. The voltages present are at the extreme edge of the relays capabilities. Caution should be exercised.
Alan, KØBG
www.k0bg.com
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RE: 1/2 Wave End-Fed Inverted V
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by AC9TS on November 25, 2004
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I also use the AH-4 but I tune a loop with mine. The same issues apply as to how much wire should be used to avoid high voltages at the tuner. Tim Ellison, W4TME, created a handy spreadsheet to display what lengths to avoid when using this tuner. The 124' you have is about 3.5 WL at 10M. If you can possibly add 6' of wire to your antenna, that would put you out of any .5WL points from 10-80M. I'm not sure as to the 160M tunability but it still may work for you. If you can clip on a piece of wire, it may be an interesting experiment.
Tom - AC9TS
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1/2 Wave End-Fed Inverted V
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by N4ZOU on November 25, 2004
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You can greatly improve this antenna by adding ladder line to it forming a ZEPP antenna. This eliminates the need of a counterpoise and lowers the very high voltage/impedance found at the end of a 1/2-wave dipole. It's very simple to make. Just make the dipole element 1/2-wavelength long for the lowest band and the ladder line feed a 1/4-wave length. Only one side of the dipole end of the ladder line gets connected to the element and the other side is left open. On the tuner side of the ladder line it will make no difference which side is connected to the ground or hot post but most people connect the open side of the ladder line to the hot post of the tuner and the groundside to the now 3/4-wave length side. I have personally tried it both ways and performance was the same either way. What your making with a ZEPP antenna is also known as a J-pole on the VHF and UHF bands! As long as the antenna is worked on a band with an odd wavelength any tuner will be able to match the impedance found at the tuner end of the ladder line. A 4:1 Balun is not required at the tuner, any tuner. If you switch to a manual "T" type (what everyone sells now) antenna tuner later you will find it works better to bypass the internal 4:1 Balun. The reason for this is the impedance will be around 75 ohms or what you would expect to see at the center of a 1/2-wave dipole. 75 ohms is much easier for the tuner to match than 18.75 ohms (+ or - due to ground coupling and other conditions around the antenna). All type feed lines connected to an unmatched impedance at the feed point of the antenna will repeat that impedance every 1/2-wavelength times the velocity factor.
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1/2 Wave End-Fed Inverted V
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by N8BOA on November 25, 2004
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How about a temination risistor to ground at the far end much like a EWE antenna would this lower the impedance at the feed and thus the high voltage. Would it also provide more foward gain??
Just thinking
P.Sean Coady
N8BOA
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RE: 1/2 Wave End-Fed Inverted V
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by AA4PB on November 25, 2004
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I doubt that a termination resistor would cause the antenna to have more forward gain. It would just eliminate the reverse lobe by turning that power into heat in the resistor.
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RE: 1/2 Wave End-Fed Inverted V
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by AA4PB on November 25, 2004
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I've done some experimenting with end fed wire antennas (invertel L) of various lengths using SGC tuners. Making the length "near" 1/2 wavelength (high impedance) lowers the current (and loss) in the radials making them less critical. As stated by others, you generally want to stay far enough away from 1/2 wavelength to lower the impedance enough that the tuner can match it.
I expect that how much improvement you see with a ZEPP configuration depends on how good a radial system you use with the end feed wire.
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RE: 1/2 Wave End-Fed Inverted V
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by K3AN on November 25, 2004
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At my last QTH, I end-fed a 130-foot wire in a "lazy L" configuration. My SGC-230 was able to find a match on all bands except one (either 30 or 17 Meters, I don't remember which). Like the previous poster, I agree that the high feedpoint impedance of an end-fed half wave (or multiple of a half wave) antenna is a benefit. It means that ground losses will be quite low, even with a minimal radial system.
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RE: 1/2 Wave End-Fed Inverted V
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by K0BG on November 25, 2004
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With respect to 160 meters and the AH-4; it is not rated to work on 160, but it will if the length of the radiator is long enough. It takes about 65 to 70 feet when fed as a mono-pole.
Alan, KØBG
www.k0bg.com
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1/2 Wave End-Fed Inverted V
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by G0GQK on November 25, 2004
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Nice to read something on these pages about amateur radio for a change. I should think everybody is getting a bit cheesed off with much of what is usually published, ham radio on its death bed, CW versus the rest, etc.etc.etc.
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RE: 1/2 Wave End-Fed Inverted V
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by VE7HJ on November 25, 2004
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Good information, I have tried using my tuner on a friends 135' flat top with 450 ohm ladderline. It did a good job tuning the antenna from 160-10 worked best on 80-meters where it was designed for. At my QTH I would need to extend the control cable and coax to use the center fed design. I am still working out the relocation of the AH-4 tuner and cables. My concern is the ladderline would have to run throught the branches to be used. I have been trying to keep the antenna system neighbour frendly.Not that I have any problems with them but its best to keep them happy.
73, VE7HJ
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RE: 1/2 Wave End-Fed Inverted V
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by N6AJR on November 25, 2004
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this is still my favorite, or variations there of.. flattop, inverted v, or sloper..
http://www.hamuniverse.com/multidipole.html
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1/2 Wave End-Fed Inverted V
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by WA1RNE on November 25, 2004
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There is a much easier way to feed an End Fed 1/2 wavelength wire: Use a parallel tuned tank circuit consisting of an air core inductor and a tuning capacitor. The inductor I normally use is the airdux variety and a good quality transmitting air variable capacitor. Don't skimp on the inductor; wire size should be #14 AWG or better to maintain a decent Q and low copper loss. Refer to an ARRL handbook or Antenna book for preferred inductor/capacitor values for the band(s) of interest. (and based upon F= 1/ 2pi*SQR[LC]
A 50 ohm line feeds the parallel tuner as follows: connect the coax shield to the bottom of the coil; tap the center conductor up a turn or 2 from the bottom to start; connect the antenna to the top of the coil and the capacitor in parallel with it; connect some 1/4 radials or a good RF ground to the ground side of the inductor.
This tuner is universal in that it can match a very high impedance - such as the end of a 1/2 wave wire to a low feed point. More taps can be added at the bottom as necessary to obtain a close match to 50 ohms and at the antenna end of the inductor.
Doesn't get much simpler and its inexpensive. Add a servo / stepper motor scheme and it can be tuned remotely.
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1/2 Wave End-Fed Inverted V
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by W3DCG on November 25, 2004
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I love these. It has helped me a bit, in seeing more clearly an idea I had. Have a tree about 60' tall.
So I was thinking, mostly non-resonant, End Fed {window or ladder-line) Zepp/Inv L. Trying to make it cover 30-80, with emphasis on 80 and 40.
Figured 55' for the Vert, and about 45' for the horizontal. Seeing on 40 it may be a higher current at bottom, thinking 4*33' radials. But there's still current also on 80m close to ground, maybe the 4 1/8 wave radials would help some there(?). Feeding with about 64' of windowline. Figure 100' total length puts more of the current toward the top of the vertical section on 80m?
But- what would happen if a roughly 65' wire were run parallel to the 55' vertical, but 10 feet would have to be bent at the top? Might that part become a mostly 40m half wave radiator? Or, because of the high impedance feed, would the current therefore flow into the closer to 3/4 wave wire?
The reason why I care, is because, of the desire to have as much of the radiation at low angles as possible, on at least two bands, 40 and 80. But on 40m, fed with 64'of window line, it appears if the idea of a 40m half wave wire did what I wished, (be a half wave vertical dipole) with low current near ground, my tuner would be seeing high Z. But there is a 4:1 current (prob small lossy?) balun in the tuner.
Anyway, if that parallel 40m half wave wire idea would not work if anyone can say- because of the impedance to the 3/4 wave wire being lower, and plus because it might act like an open wire transmission line so therefore cancellation would yield very little radiation, then- scratching the "add a 1/2 radiating 40m wire" idea and going back to the single 55'Vert+45'Horizontal- on 40m it looks like a current null closer to the middle of the 55' vert section with high current at the base then at the top and slightly beyond the horizontal bend.
So what does that do to the radiation pattern on 40m? Does it mean like a 3rd of the radiated power is at low angle, a 3rd of it is aimed into the ground at a specific radius, and the other third is aimed like a quarter wave horizontal (on 40m)?
Any thoughts at all on any part? Tuner range is 6-1600 ohms, 3908pF max Capacitance and 24.86 microHenrys.
On 80m it looks like high Z at the tuner.
Prob doable given the 4:1 balun, who knows how much loss?
On 40m, it's closer to lower Z at the tuner, now the 4:1 balun may or may not be good, but- it's a high Z transmission line, so would the 4:1 balun still be handy? My Uncle/Elmer, never one to do my work for me turned me on to a most interesting place, and it appears to my layman's eyes that probably-
G4FGQ has given us the tools to find out most of the answers:
http://www.smeter.net/antennas/antennas.php
Those pages are awesome... I know I've become so absorbed there lately, for so long my vision started to blurr! The programs there, however, help, albeit via plug and chug- to understand what happens when various factors such as length, radials, frequency, coils, diameters of various antenna parts in various configurations, various transmission lines, are changed.
This Thanksgiving, among many items for which I am thankful, I am also, very thankful for G4FGQ's tools. What a great person. And thankful for K4AQ for pointing me in that direction. Cheers and 73!
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1/2 Wave End-Fed Inverted V
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by N9WB on November 26, 2004
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I assume that you are using 50-OHM coax? How long is the coax? Why the counterpoise? I wonder why the 4th counterpoise wire reduced the performance?
Vy 73, Walt N9WB
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RE: 1/2 Wave End-Fed Inverted V
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by N9WB on November 26, 2004
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OOPS, I missed the fact that it was end fed. That's why the counterpoise.
Walt N9WB
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RE: 1/2 Wave End-Fed Inverted V
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by AE1X on November 26, 2004
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25 years ago I employed a 180' length of wire end fed. I employed a simple L matching network set up to have multiple configurations. It tuned all bands 160 thru 10 meters, though I used in mostly on 160 thru 40mtrs because I had an HQ1 mini-quad for 20 and above. I did not have any ground radials. The ground consisted of a copper rod driven into the ground right outside my shack.
The L matching network consisted of a roller inductor and couple of good transmitting variables mounted on a large steel chassis, in fact I still have it. The configurations consisted of high-Z match, low-Z match and a parallel network with the input employing the tuner tap as a sliding tap to match to step down the high-Z to 50 ohms. The later configuration worked well on 160mtrs. I worked plenty of stations on all bands with that system.
When I moved, I put up 90' of wire at my new QTH and again worked all bands. I had many great contacts with stations on the west coast late at night on 75mtrs including stations in KL7 and KH6. So using a lenght of wire and a multi-purpose tuner will bring lots of great contacts.
Ken
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1/2 Wave End-Fed Inverted V
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by W7ZZT on November 26, 2004
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Great article. I've been experimenting with 1/2 wave wire antennas for my 817 while travelling on business. The most fun I've had is building a Fuchs Antenna which is a 1/2 wave single wire coupled with an antenna tuner. Do a Google on Fuchs Antenna and you'll get several references to research.
The tuner and wire are easy to pack for portable operations and the performance is really quite good at the 5 watt level. Also, performs well in a horizontal or vertical orientation. I did have intitial concerns about high voltage but so far, my finals are intact.
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RE: 1/2 Wave End-Fed Inverted V
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by W6TH on November 26, 2004
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1/2 Wave End-Fed Inverted V
I have two of these end fed 1/2 wave antennas. One as a inverted V and the other horizontal. The horizontal works much better. I don't use any counterpoise on either. I tune both with a MFJ-941B or my MFJ-962 for the higher power. These antennas are as old as the hills of California; inexpensive, efficient and gain as to a long wire on the higher frequency bands.
.:
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1/2 Wave End-Fed Inverted V
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by WA2JJH on November 26, 2004
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I have seen many do very well with inverted V's.
If constructed correctly, it should preset a 1:1.5 or better match for the band you cut it for.
The formula found to work well, was simply 2 quarter wave length's of the band you are using.
If your not using a balun, have the center conductor and shield 1/4 wavelegths have about a 45 dgree angle.
The ends of the wires should be a minimum of 1 wave length above ground.
I have found cutting the lengths for bottom end of the band, will give a 1:1.5 or better in the center of the band.
If done right, you should be able to build a 15M inverted V that will have a better than 2:1 SWR on any part of the band with no tuner.
This is only my experience, when I had space to put one up. The DX was most excellent.
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RE: 1/2 Wave End-Fed Inverted V
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by W5AH on November 26, 2004
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Ground the far end , put radials under both ends and feed it with 50 ohm coax for single band operation. (ARRL Antenna compendium volume 2, page 88)
Bob
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RE: 1/2 Wave End-Fed Inverted V
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by KI7YY on November 27, 2004
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Sounds great, and thanks for the report on your antenna. The way the article reads it sounds as though the inverted V might be slanted somewhat like an end fed V-Beam. Is this the case? If so do you notice any directivity? 73, KI7YY, Kirk
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RE: 1/2 Wave End-Fed Inverted V
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by VE7HJ on November 27, 2004
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Kirk, yes it is directive towards the low end of the slope and the far end of the wire. I am located in CN89 Vancouver BC. I now hear lots of east coast stations and have worked 160, 80, 40, 30, 20, 17, 15, 12 and ten meters.
The end fed antenna does not require a counterpoise for the band that the 1/2 is cut for. If you intent to work the antenna as a multiband you will need to put a minimum of 3 counterpoise wires 1/4 wave on the lowest band. I am told that the use of a matching transformer would improve the balancing of the wire to a tuner at 50 ohms. I use a wire tuner which works but could be stressing the tuner with a high SWR. Wire antennas are always a lot of fun to play with.
73, VE7HJ
James
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1/2 Wave End-Fed Inverted V
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by AB1AW on November 27, 2004
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I found that endfed half wave antennas can be quite effective and versatile, especially for QRP operation where RFI is not as big an issue. I use a 130 foot end fed for operation on 80m, 40, 30, 20, and 10m with a simple parallel tuned circuit for the tuner.
End fed half wave antennas can also be physically shortened, just like loaded dipoles. For example, you can cut the physical length of an 80 meter end fed antenna from about 130 feet to about 65 feet by putting a couple of 44 uH coils, each placed halfway from the center of the antenna. I described this in depth in an article in May 2004 QST.
The ARRL antenna handbook (and other publications) has charts and graphs for determining the lengths and coil inductances for short loaded dipoles.
Mike Polia
AB1AW
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1/2 Wave End-Fed Inverted V
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by VK1OD on November 27, 2004
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Sounds like the wire is close to its first parallel resonance on the 80m band.
You may see advice in the manual to avoid parallel resonances, because they result in high feedpoint voltages, stressing the tuner capacitors.
I did some modelling to find out how end fed wires of a couple of configurations work, you may be interested in models of an Inverted L which visit the major loss components and the determinants of lowest usable frequency (and plots feedpoint voltage). The article is at http://www.vk1od.net/InvertedL/InvertedL.htm .
Owen
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RE: 1/2 Wave End-Fed Inverted V
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by KB9WIS on March 27, 2005
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WA1RNE,
I would like some more information on what values to use, for the parallel scheme you've mentioned.. Do you have an e-mail address, or could you send me an e-mail to:
scott231us@yahoo.com
I would like to try this method, as I'm sure it may be a tad better than trying to using 1/4 stub transformers all the time.
Thanks,
kb9wis
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1/2 Wave End-Fed Inverted V
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by NG9D on December 6, 2005
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Great postings - very enjoyable reading!
Maybe I should now begin describing my antenna as an end-fed inverted-V! I have been referring to it in QSO's as an "inverted-L".
The total length is roughly 5/4 wavelength on 40m and the apex is 75 feet from the far-end of the wire. The total height is about 42 feet and the included angle must be somewhat less than 40 degrees. The far-end droops down to say 12 feet from ground. The antenna is fed via an MFJ941C tuner.
In any case, I have been using it on 40m CW a lot with my new T-KIT 1340 and it radiates 4W pretty well.
So, I decided to try it with my (ancient) 350 milliwatt, two transistor, transmitter (same circuit used in "TUNA TIN" rigs). I had a couple nice QSO's including a 40 minute long ragchew with Rob, W8YRB, who said:
"Fantastic ... Your signal was peaking an S9 on occasion, but never dropped below S5. Hope you're as pleased with the sound as I was and I sure was surprised on how your rig was performing."
Of course the fact that Rob was using a 4 element wire Yagi aimed right at me probably didn't hurt either!
My 0.35 watt transmitter and tuner are positioned about 10 feet from the city's copper water pipe which apparently makes a useful ground. The QRP transmitter doesn't make enough power to even deflect the meter in the tuner, but both my T-Kit 4W rig or ICOM 740 80W do. And with them the MFJ tuner can be adjusted on 40m to an "SWR" reading of ~ 1:1. I've been getting a lot of good reports using the 4W T-Kit.
The inverted-L -- I mean V! -- also tunes on other bands. I made some 160m and 80m contacts. I made a few 20m CW contacts with it using a Ramsey QRP transmitter (3/4 W). I guess on 20m this antenna is about 5/2 wavelength long.
But I am mainly experimenting with it on 40m now. In comparison to my 1/4 wave vertical, it seems to do somewhat better by ear, but I haven't recorded any actual measurements yet.
Alligator clips, just outside the window, allow me to disconnect the antenna from the tuner and clip it to a copper ground rod when not in use. I hope it survives the weather this winter.
73 NG9D
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