Message-ID: <000501c1f101$34cd0fc0$c947073e@default>
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: "LF-Group" <rsgb_lf_group@blacksheep.org>
Subject: LF: TV SMPSU QRM...idea??
Date: Wed, 1 May 2002 12:12:31 +0100
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Hi all, is is not always very easy to use the to reject the the drifty
harmonics of SMPSUs from the 136 received signal. I discussed a couple of
ideas with Steve, GW4ALG but we did not pursue them further at the time.

My suggestion was to receive the local interference on its fundamental
frequency maybe 35kHz or 70khz, then multiply it up before subtracting it
from the 136kHz incoming signal.  I am not sure how easy it would be to do
this (or even whether it is really feasible). There are obviously problems
and certainly I cannot think of an easy way of multiplying the signal other
than mixing it with itself. Maybe someone cleverer than I could see a
solution, and even see whether it would be a useful tool. The advantage as I
see it would be that the signals are very strong on the fundamental, and
easy to separate from genuine radio signals at that frequency.  Only a
narrow band of signals at 34,45.3,and / or  68kHz need be 'collected.After
processing the system should not reject any real wanted 136kHz signals.  It
is also possible that this susyem would deal with multiple sources of qrm,
which is the shortcomming of the simple phasing system.

Go one ....tell be I am off my trolley...but please explain why !!

Cheers de Alan G3NYK
alan.melia@btinternet.com