How do television detectors work ?

[username]

How is it possible that TV detector's work like the ones used by the TV licensing vans, is it by measuring the TV broadcast signals power loss ?

 

[J-Man]

http://www.tv-l.co.uk/tvlic/penalties/detection_tvvans.html
http://www.sciencenet.org.uk/database/Technology/Original/t00033d.html

Isn't broadcast television free to the receiver in the U.K. as it is in the U.S.A.?
I've never heard of an unlicenced broadcast reception. (Satellite or cable sure, but broadcast?)

 

[username]

Here in the UK you have to buy a license each year for the broadcast receiving equipment.A colour TV is more expensive than black and white TV, to top it all off we only get two advertising free channels, the other three have lots of adverts :(

 

[russ_watters]

Was your original question about pirating the signal directly from a news van? They use different frequencies than your tv tuner. They're microwave. Thats why they have the long supports - they're highly directional.

 

[username]

Originally posted by russ_watters
Was your original question about pirating the signal directly from a news van? They use different frequencies than your tv tuner. They're microwave. Thats why they have the long supports - they're highly directional.

No. I thought that as the TV receives the broadcast signal and creates a picture out of it, this would result in the broadcasts signal strength being diminished (which could be detected). But I stand corrected.

 

[J-Man]

Originally posted by username
Here in the UK you have to buy a license each year for the broadcast receiving equipment.A colour TV is more expensive than black and white TV, to top it all off we only get two advertising free channels, the other three have lots of adverts :(

I never knew that. Live-and-learn.
Is this representative of Europe in general? (You don't learn these things staying in hotels.)

 

[Tyger]

i think he means

how can they tell if you're pirating programs. Well your converter or television set uses an intermediate frequency and the frequency converter circuit produces that frequency and the other difference frequency. And the van has a reciever which can detect the other difference frequency and tell what channel you are watching.


It's an old trick that was used for detecting radio recievers during WWII.

 

[Tyro]

Does that mean that computers with a TV card can not be detected? Or does the TV card itself have the intermediate 39MHz frequency as well? If you keep your computer's casing closed shouldn't it shield it from signals from the detector van?