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KG6BAJ > NWSGRP 02.08.09 22:20l 48 Lines 1764 Bytes #999 (0) @ WW
BID : 9486_N1OES
Read: GUEST
Subj: Re: Counterpoise for an end-fed wire antenna
Path: DB0FHN<DB0MRW<DK0WUE<DB0RES<IK2XDE<PY1AYH<PY1AYH<CX2SA<KD4GCA<KG6BAJ<
KG6BAJ
Sent: 090802/1200Z @:KG6BAJ.#NCA.CA.USA.NOAM #:9486 [Grass Valley] InterGate $:
** NEWSGROUP: rec.radio.amateur.antenna
** FROM : "Geoffrey S. Mendelson" <gsm@mendelson.com>
KJ4NTS wrote:
> I'm confused about the requirements for a counterpoise for an end-fed wire antenna. I understand
> that it's needed, but I don't understand what the requirements are.
If you get 100 replies, you'll probably get 110 different answers to that.
> Can a ground stake at the base of the feed point serve as a counterpoise, or does it need to be
> another wire running under the ground below the antenna?
No, it makes a good DC ground for lightening protection. A counterpoise can be
run almost anywhere, and the more the better.
> If a wire is required, how long does the counterpoise have to be?
.28 wavelength is something I have read, while most people use 1/4 wavelength,
or an electrical equivalent (shorter due to velocity factor).
> Would it be better to use insulated or uninsulated wire for a buried counterpoise?
Uninsulated.
Not that some antennas don't need a counterpoise, for example a 5/8th wave
antenna or an end fed zepp which uses no or a very short counterpoise.
A friend of mine has a commercial antenna, which consists of a matching
network, a trap and around 40 feet of wire. It covers 10,20 and 40 meters
with no counterpoise. The matching network can only handle 25 watts,
My speculation is that it's sort of a 5/8th wave type antenna with
loading coils to eletrically lengthen it.
It could also be a 50 ohm 25 watt resistor with a long tail on the "hot" end,
but I really doubt it.
Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM
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