Message-ID: <B333AB0EF6D4D4118BAF00508BAED8EA088D9EEF@mms12014.stv.uk.astrium.corp>
From: "OSBORN, Chris" <Chris.OSBORN@astrium.eads.net>
To: "LF Group (E-mail)" <rsgb_lf_group@blacksheep.org>
Date: Fri, 19 Nov 2004 09:03:01 -0000
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Subject: LF: Receiving loop aerial - improvements
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	Hello LF Group

	I use a simple home built D.C. receiver for the 136 kHz band and the
selectivity is rather poor.
	I built G3LNP's excellent rx loop when it was first published in
RadCom in 1999 and it works fine.
	I then made a remote rotator for it using a power op amp one end and
a tape recorder motor with worm and wheel at the other - I can resolve
            to about one degree with practice
	The whole set up is quite good considering it's simplicity but I
still get considerable breakthrough from the commercial signals.

	The 'LNP loop had a second winding to null the Radio 2 long wave
signal (if I recall) and I have never found it necessary to use this
winding.
	The other week I fed the output from the loop amplifier back through
the second winding via a small trimmer (20 pF) to ground.
	This made the loop regenerative and in my opinion greatly sharpened
the response and improved the sensitivity.

	I wonder why regenerative loops aren't used more often - or perhaps
they are !

	73 Chris G3XIZ