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I recently tried using an earth ground (wire in the ground) to ground my EFHW. It does work on any band except 10 and 15 meters.

So, I think the wire in the ground is working but can I improve it? I read online that real earth grounds have rods that are ~8 feet long. Mine is about 1/2 of a foot long. Maybe increasing the length so it will also work on 10 and 15 meters? Or will it lower the static?

I know about this post but it is about a vertical and not an EFHW.

My EFHW is ~60 feet long. I am using a 40:1 transformer.

What is a counterpoise?

It is ~8 feet above ground at the feed-point. I don't know is it is vertically polarized. The feed-point is not choked.

Mike Waters
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John Doe
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3 Answers3

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No, an earth ground will not work. The earth ground is for lightning protection, nothing else. An EFHW antenna is an Extreme Off Center Dipole. The counterpoise on an EFHW is the short end of the dipole of .05 wavelength. You have a 40/20/10 meter EFHW antenna requiring a 7-foot counterpoise.

You can use the coax shield with a properly placed choke 7-feet from the feed point. I use a counterpoise and a choke to prevent RF in the shack. Here is a document you need to read and forget about dirt. EFHW Document

Peter Bagyinszki
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In the first place, a ground rod pounded into the earth is a terrible RF ground. Your six inch ground rod isn't even a good lightning protection rod. Really.

Secondly, an 8' ground wire is going to have an impedance and standing waves on it. In other words, even if your ground rod could be changed to a good RF ground, the low potential at the ground rod would not be the same where it is connected to the antenna feedline.

There's a lot of misinformation on the web and on the ham bands. May I suggest that you study the Grounds section at w8ji.com.

Mike Waters
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An EFHW, like most high-up horizontal dipole-type antennas, doesn't really need a ground-in-the-earth to work properly. The whole antenna is up in the sky, the currents are horizontal. It has no need to be connected to the ground, which is not part of the antenna and too far away to matter (to the currents in the wires... of course the ground also interacts with the fields).

A vertical antenna needs a good ground as its counterpoise. Ideally this would be >100 >half-wavelength wires just above the ground, but a couple of wires laid out in a few directions will also work. A ground rod or two might also work, depending on the soil conductivity, but as with mains electricity, for ground rods to work properly you need some length in contact with the ground. A 6 inch ground rod is not going to do anything at RF. 3 x 8 feet rods would be better. Still not as good as ground radials.

(Fun comment - on fairly dry ground, I've found that HF wire / dipole ntennas work quite well just lying on the ground. Certainly more lossy than at a proper elevation, but at 40 m a proper elevation is hard to achieve anyway).

In my limited EFHW experience, the type of counterpoise affected the antenna mostly outside its resonant bands. The antenna response was much better behaved (nice smooth high SWR) when it had a big counterpoise. With just the coax and shack as counterpoise, or with just 2 m of cable and a battery powered VNA, the SWR had additional dips in various places, all unstable and sensitive to me touching the coax.
At the resonant points (7, 14, 21, 28 MHz in this case) the performance was about the same with and without the bigger counterpoise.

You should still ground your antenna and shack for lightning protection, complying to your local electrical code. And depending on the way that the cable runs, it may help to ground it along the way to prevent any leftover RF from getting back to the shack and into your microphone cable.

tomnexus
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