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Old 30th Jul 2020, 3:51 pm   #15
Join Date: Mar 2015
Location: Milton Keynes, Buckinghamshire, UK.
Posts: 69
Default Re: Marconi TF2431 Counter Service Manual / Schematic

Today I fabricated a half wave dipole cut to resonate at around 100MHz and hooked it up to my scope.
Guess what? I can see the same interference signal that's been bugging the counter.

The strange thing is that as I rotate the dipole the signal maximum occurs when it's oriented North/South. The closest VHF broadcast transmitter is Bow Brickhill which is to the South East. I have an FM antenna in my loft for my stereo system which points towards Bow Brickhill.
There are VHF broadcast transmitters at Northampton to the North or High Wycombe to the South but I would not expect a particularly high signal strength.

I suspect there is some other transmitter in the vicinity operating just above the normal FM broacast band.
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