Message-ID: <007601c95709$acc95e50$0301a8c0@mal769a60aa920>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <fc7eccec0812050822x39e4cc98xc36b36cf0e73d6fa@mail.gmail.com>
Date: Fri, 5 Dec 2008 18:45:41 -0000
MIME-Version: 1.0
Subject: LF: Re: E field active antennas
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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" <andy.g4jnt@googlemail.com>
To: <rsgb_lf_group@blacksheep.org>
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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