Sunday, 1 February 2009

The W3EDP 85-ft end-fed


This is one of my favourite, cheap antennas. I have been using one for years and they don’t get much simpler.

Mine was catapulted over the roof at this QTH. It goes out of the ground-floor shack window, straight up, over the roof and then down to the end of the garden where it is tied off with fishing line, leaving the end about 10 ft high. The counterpoise goes off at 90 degrees (see illustration).

At the last QTH it went 50ft up into an oak tree. It is very stealthy and a firm favourite of the QRP fraternity.

It consists of an 85ft wire fed against a 17ft counterpoise. Some books say that you don’t use the counterpoise at all on 10m. Others say that you use a 6.5ft counterpoise on 20m. You do need an ATU though.

Some even say that you should feed it as a balanced antenna through a balun, rather than as an end fed with the counterpoise connected to the earth terminal.

I have tried it both ways and it seems to work either way. The tuning is slightly twitchier using it as a balanced antenna.

The antenna works well on 80m and 40m and even gives a dipole a run for its money on 20m. I am writing this as I listen to US stations on 20m and Californian and Michigan stations are actually slightly louder on the W3EDP rather than the 20m dipole.

DX worked on this £5 wonder include 6W/DL4JS Senegal, YK9G Syria, VQ5XF Turks and Caicos, VP6DX Ducie Island and VQ9JC Diego Garcia.

The downside of the W3EDP is that it can be noisier than a dipole and watch for RF in the shack. Running it with an earth wire to a stake and a counterpoise my field strength meter shows that it isn’t too bad though. Try one.

3 comments:

  1. Scott Carpenter M6OZI12 February 2011 14:42

    "Running it with an earth wire to a stake and a counterpoise my field strength meter shows that it isn’t too bad though."

    Hi Steve, I have your antenna book and because of that built the W3EDP, and its allowed me to get on multiple bands for the first time, and keep the wife happy (its less intrusive than a dipole in the middle of the garden).

    But I have one question - to what connection do I put that earth stake? I'm using a tuner of course, and the GND of that is connected to the 17ft counterpoise. Does the earth line go there? Or to the transmitters earth?

    all the best

    Scott M6OZI scottnjill2004@btinternet.com

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  2. awesome post! Here's how I did my W3EDP http://vurl.me/BECK. I reference your article. I would be interested in your NEC2 file if you have one for the antenna model you created. I did a couple of models, but was unsure if I was correctly 'feeding' the antenna. Also check out the link to an email on QRP-L from 1998 about the W3EDP. Could help you explain the 'rf in the shack' from the 'counterpoise' (hint, it's not a counterpoise!) ;)

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  3. I tried using your website for giving my views, but it refused to recognise my URL, probably because I am not familiar with the procedure and I don’t know what an URL is. I don’t have a website. Anyway, here is my two pennyworth.

    The “magic length” of 85 feet can also be used effectively for a doublet. Half the length of the top plus one leg of the feeder equals 85 feet, taking into account the velocity factor of the feeder, which should be parallel feed, such as 300 ohm ribbon or open wire.
    My top is 102 feet and the 300 ohm feeder 30 feet. It tunes up easily on 80, 40 and 20 metres with a T match ATU. Obviously, no counterpoise is needed with this balanced antenna.

    Best wishes,
    Derek Love. G0DRA

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