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
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