Mal,

With all due respect for your undoubted high opinion of your own professional expertise might I suggest that you perhaps enquire as to Andy's credentials before wasting space/time/bandwidth trying to teach his grandmother to suck eggs.

73 de  Pat g4gvw

Try a piece of wire as long and high as possible and an ATU this is superior to any active antenna or loop for that matter, the loop only helps in a noisy environment, and even then not always. 
G3KEV 
 
----- Original Message ----- From: "Andy Talbot" <[email protected]> 
To: <[email protected]> 
Sent: Friday, December 05, 2008 4:22 PM 
Subject: LF: E field active antennas 
 
> Having just had to make an active antenna for HF (for gainful 
> employment-type work, not Am. radio purposes. The commercially made 
> one we've ordered is on five weeks delivery and it was needed before 
> yesterday) I was wondering about a helical element. 
> 
> As the thing had to be resonably lightweight, I made the antenna 
> element from copper tape on 15mm plastic water pipe rather than use a 
> solid copper tube. Just for a bit of novelty I wound the tape in a 
> helix, but then started wondering if doing that would make any 
> difference to performance. Normally, helically winding an antenna 
> (rubber duck type at V/UHF) only serves to distribute loading 
> inductance into a short antenna to make it resonate - unlikely to 
> change improve the loss terms at all. But I did wonder if the added 
> extra inductance, or increased conductor length (not element length - 
> that is 1.2m) would change the performance significantly from a 
> straight tube. 
> 
> Does anyone have any ideas - food for thought if nothing else? The 
> base amplifier is one I've used several times before for V/LF up to HF 
> based around a J310 source follower running at 20mA with bootstrapped 
> input followed by a 2N5109 emiter follower at Ic = 80mA. I may have 
> published it way-back-when in the amateur press in the 73kHz days. 
> Not the best design judging by some of those published in more recent 
> years, but did mean all the components were to hand for an instant 
> job. 
> 
> Andy G4JNT 
> www.scrbg.org/g4jnt 
> 
 
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