40-80 EFHW - Help!

What frequency does it resonate on, if you are using plastic covered wire it might need to be quite a bit shorter than the calculated value for bare wire

73 Colin

I have made a couple of these and they work great Multiband half wave end-fed HWEF (2012) | PA3HHO's

Terry G4 POP
Log4om Development Team

Hi Coiln. It’s 22.28m, plastic coated, which allowing for the 5% correction give resonance at 7.087MHz, near enough 7.1. The wire tunes up fine on my son’s wire tuner.

73 John MW0XOT

Mine is a little different, following:

This uses a 3/24 winding, which is supposed to be better for the low frequencies. The graphs seems to bear this our, but not with my tuner! I’ve tried a fixed cap (100pF), a polyvaricon (similar results) and checked continuity. I might just wind a new transformer just to see if that’s the problem. Two coils and a capacity. How simple is that!

73 John MW0XOT

Here is a picture of mine that worked a charm before I lost it on Torlum Hill.

The toriod is a T68-6. The primary is 3 turns of 7/0.1 PVC wire. The secondary is 24 turns 16SWG ECCW. Th capacitor is an unknown polyvaricon. The secondary is evenly spread over the toroid, the primary is wound over that. The BNC connects to the primary alone, i.e. it’s a transformer with no common earth. The secondary connects to the 4mm terminals and the capacitor is connected in parallel with the secondary.

Originally made for a 20m EFHW with 10m of wire in a V using a 5m pole to support the middle. Later used with 5m of the same yellow wire supported vertically for on the 5m pole.

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That’s a really neat and compact unit.

Hi John,
If the transformer is working into a resistive load it is doing the impedance transformation 50ohm to 4k7 or whatever resistor you used. I think your wire is a little long, I’ve just looked online at some dipole calculators and they are coming up with 20.28 metres for a horizontal dipole and 19.26 metres for an inverted vee, I could be wrong, but it might be worth shortening it by 10 feet or so (fold the wire back along itself) and see if things improve.


I think you must be right Colin. I’ve just tried the on-line calculator that I found worked fine for my 40 dipole and it gives me 19.08m for inverted V configuration, which is what I was using for the test. That would certainly explain the unexpected very low SWR at just over 6 megs. Durhhhhhhh! I think I’ve just had a Homer Simpson moment. So, sometimes the reason you can’t find out why something doesn’t work is because… it is actually working. I’ll test again tomorrow and let you know.

At last I’ve made the W3EDP. Unfortunately I cannot get a reasonable swr on 80m. The polyvaricon I used is a 8-285 pF twin-ganged. Using just one side I got 1.2:1 on 40m and 1.5:1 on 60m. The 40m match was on minimum capacitance. 80m would not give me any sort of match I then tried linking the two sides of the polyvaricon to make it 16-570 pF. On 40m the SWR at minimum was 2.1:1 (expected), 60m would still match at 1.5:1 and 80m gave some sort of match but best SWR 19:1! I’m thinking I might need to looks at the coil (20t on a film container with 3t tap) but I would appreciate any comments you might be able to make before I make matters worse! Thanks Brian.

Brian, before you butcher the coil, I just looked out an old article on the W3EDP by G3BDQ. In the original version there was a single fixed counterpoise but in those days they had fewer bands. His version had a length of 25.6m for the antenna and these lengths for the counterpoise:

3.5 MHz…5.18m
18…1.98m or none.

When I built my version I had trouble with 80m, too. I found two solutions, the first one was to make the counterpoise variable by making it longer than necessary but winding it off an old wire spool. This works well and enables me to tune all bands, but on a summit it is a nuisance to play around with, so I looked for another way. What I did was put another variable cap in series with the antenna socket in the box, and add a shorting switch. If I can’t get a good SWR with the fixed 5.18 metre counterpoise I open the shorting switch and bring the second capacitor into play. This solved the problem.

My tuner is a little on the big side because I use two air spaced brass and ceramic variable caps that I used in a homebrew short wave TRF receiver over 50 years ago, but they let me use the antenna with 100 watts from an 857. The coil is 22 turns on a plastic 35mm film canister, the caps are about 100pf, and I can get a low SWR on 80, 60, 40, 30 and 20 metres - though you need safe-crackers fingers on 20! :grinning:

Your simplest option now is to vary the length of the counterpoise to get your match.



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My Inverted L 1/2 40m worked on 80m at 1/4w with 22m of wire but only 11m is actually L’ed off the pole saving space.

So does me vert 1/4w vert work on 80 but only 1/8w with 11m of wire and with my positive result from G/DC-003 10w into VK5PAS on 20m off its first contact ever off a sota summit

Now both antennas can be run off the squid pole and the 9:1 Unun just remove one and set up the other simple,s small and light weight. Whole idea is if got room for the bigger inverted L 1/2w 40m antenna, away ya go, if not use the 1/4w 40 Vert

Tunes in with me ACU on all bands not problem via the one 9:1 Unun off a 8m squiddy pole and the 11m contour poise to which is now a four way counterpoise totaling still 11m set for 40m, but got now extentions for the CP if go down to 80m.

still experimenting


Hi Brian,
Here’s a newbie type question … would a counterpoise made up of 1 x 5.18m + 1 x 7m + 1 x 1.98m lead not cover all of the bands? I know StepIO take this approach with their vertical antenna - actually 4 wires for each length required if I remember correctly - these are not switched as far as I know rather they are all connected to a ring at the bottom on the antenna, where the puter of the coax is also attached.

(Karl - out of interest, I jut tried the 40m loop on 80m and 160m and the internal ACU in the rig matches on those bands and the receive signal strength comes up. This was not the case when I had the Q-Section in place only after adding the 3:1 Balun).


I have never actually tried that, Ed, in theory it should work OK if the counterpoise lengths are correct but I think that the given lengths just reflect one particular set-up and should be taken as a starting point. As I see it, the counterpoise is part of the radiating system so if it is laid on the ground it will not act the same as if it was some metres up in the air, and its performance will vary with the conductivity of the ground beneath it. It is similar to a quarter-wave vertical, which works differently if the radials are elevated compared with buried radials. This is why I tried out the second variable cap, which is easier to adjust on a summit compared with adjusting the counterpoise.


Nice one ed tried the 4:1 balun with ladder feeder 300hm no work. Like said going to make one to go onto the loop and then coax feed down from there keeping the run short.

Mine tunes down no problems on 80m me loop.


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Thanks very much for all your advice. I like the size of the W3EDP over the EFHW (I made both) and I’ll persevere with your suggestions. Now all I need if for HF to be working when I test it all. John MW0XOT