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Old 1st Aug 2011, 3:41 pm   #8
Skywave
Rest in Peace
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,457
Default Re: TV Detector Vans

Quote, Sideband: "I know it was possible to detect timebase noise but it's doubtfull if you could actually determine which channel someone was tuned to".

I'm not so sure about that, SB.

The local osc. will almost certainly radiate some of its signal from the aerial - albeit at a significantly reduced level, but enough for a sensitive receiver to find it and then do the necessary D.F.
In a parallel vein, at about the period in question, when I used my Eddystone 888A receiver on 10 metres with a 110' 'longwire', it used to completely block out TV reception downstairs - much to the annoyance of my parents - and the TV received field strength was substantial - you could see the TV TX mast on the nearby hill from the lounge window!

Morever, the technique of 'electronics evesdropping' (and its prevention) has been used for many years by various Government Security Agencies: look up 'Tempest' on the 'Net: same principles are involved.

Al.

Last edited by Skywave; 1st Aug 2011 at 3:52 pm. Reason: Add quote & last para.
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