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G0IFI > HELP 05.04.07 01:57l 28 Lines 937 Bytes #999 (0) @ WW
BID : 51267-GB7SYP
Read: GUEST
Subj: re: 1/2 wave end fed (FTD)
Path: DB0FHN<DB0FOR<DB0SIF<DB0EAM<DB0SMG<DB0RES<DB0GOS<ON0AR<GB7SYP
Sent: 070404/1702Z @:GB7SYP.#19.GBR.EU #:51267 [Barnsley Local] $:51267-GB7SYP
From: G0IFI@GB7SYP.#19.GBR.EU
To : HELP@WW
GM7HUD wrote:
>
>Time for the silly question... Perhaps I've missed this bit, but do you
>need a counterpoise or earth connection?
>
I think this was dealt with earlier, but a 1/2 wave antenna is a "whole" antenna, therefore it doesn't need a counterpoise.
A centre fed 1/2 wave dipole is low impedance, low voltage, therefore high current, whereas an endfed will be high
impedance, low current, high voltage.
I took one of the 10 metre ones apart once, and the feed is simply a series coil between the atenna element and the metal
bracket/outer of coax, with a tap for the centre coax feed about 1/3 of the windings from the 'earthy' end, if that makes
sense. I think the coil had about 8 windings of something like 6mm single strand copper wire on a 2 inch diameter former.
I reckon you could get a 20m version matched pretty easily with a bit of cut and try.
73 Perry G0IFI
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