servodude wrote:scotia wrote:AleisterCrowley wrote:As for TV Detector Vans - not sure they ever really worked - and they almost certainly wouldn't now ...
About 65 years ago I saw a TV detector Van - theoretically in action. It was evening, and a Fish & Chip Van was making its rounds in our street. As we patiently queued for our chips, a Van (with large lettering declaring that it was a TV Detector Van) drew up, and its occupant joined the queue. He loudly proclaimed that they had a technical hitch, so their apparatus wasn't working - but they would get it repaired and would be back the next day. Presumably a number of licences were hurriedly purchased the following day. I didn't see the detector Van again.
We covered the principles of how they "could" work in comms as undergrads; with the caveat that the actually "worked" as a threat.
Certainly there's nothing emitting from a post CRT TV in any amplitude that you could use to identify a TV from a distance.
I suppose a low-tech way, when there were only three channels, could have been to correlate the flickering from the curtains with the flickering of each channel's picture.
Along the same lines, and also being a bit facetious here, one thing that emits from a post CRT TV is light, so if they manage to peek in through a window they could "detect" it. Maybe the detector in a TV detector van is the driver!