Message-ID: <001f01c0cfca$3bb5fda0$f4eb7ad5@dave>
From: "Dave Sergeant" <dsergeant@btinternet.com>
To: "rsgb_lf_group" <rsgb_lf_group@blacksheep.org>
References: <001c01c0cee7$3843ab60$ba62883e@g3aqc> <000601c0cf47$124ae620$a7ce28c3@ericadodd>
Subject: LF: Re: Re: Re. Pre-amps
Date: Sat, 28 Apr 2001 11:00:47 +0100
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>From Dave G3YMC

Peter G3LDO wrote:
>I have made a number of LF loops and have not had much luck with pre-amps;
>they all seemed a bit noisy or I found there were lots of signals around
>that shouldn't be there

This probably shows the problems of preamps which are broadband with no
selectivity other than that of the loop itself.  My transverter does have a
preamp in it, but it is preceded and followed by a parallel tuned circuit at
136.  A minimum of two tuned circuits was found to be necessary to get rid
of the 60kHz/198kHz intermod product on 138kHz.  I suspect, apart from
Luxembourg effects we often see on DCF39, most of the reported problems with
IMPs from the BC band (not just loop preamps) are due to insufficient front
end selectivity.

I am following this thread with interest because as you know I use my
transmitting loop as an excellent receive antenna.  I do not (yet) have a
vertical resonant antenna for the band - I would be interested in Steve
GW4ALG has any problems in loop detuning from his main antenna, as his loop
is of similar dimensions to mine.

73s Dave G3YMC
dsergeant@btinternet.com
dsergeant@iee.org
http://www.dsergeant.btinternet.co.uk