At 9:57 am -0600 26/2/01, Christian M. M. Brady wrote:
>On 2/26/01 9:09 AM, "Gary" <[EMAIL PROTECTED]> wrote:
>
>> Again, pa shaw! Pa shaw to the paranoiacs who think that some white van
>> outside is "reading the flux" on their monitors.
>
>Well, I don't know about reading the flux, but in England there are white
>vans that go around "reading" whether or not you have a TV in your house
>(via signals of some sort I assume) and, if you have not paid your TV
>license, they will then send you a fine.
Sorry to disappoint you Christian, but the TV detector vans cannot
see what is on your screen. TV tuners are SuperHet receivers, which
means they work by mixing the incoming high frequency with a locally
produced 'local oscillator signal' to produce a lower frequency
harmonic that can be handled more easily and accurately (This is a
very brief and not too technical 'laymans' explanation. Please do not
write back to correct me on this, I know it's not 100% accurate!).
The TV detector vans pick up the signal from this local oscillator
(which inevitable broadcasts out through the aerial.
The TV Detector vans tune in to this signal using highly direction
aerial (or even hand held portable scanners), and because it is set
at about 40MHz above the channel tuned in, it is easy for them to
know which channel you are watching.
They have no way of reproducing what is visible on you screen.
Having said that, I am sure that I saw a demonstration of electronic
eavesdropping on the excellent BBC TV series 'Tomorrows World' many
years ago that did demonstrate how a fuzzy, flickering picture could
be picked up remotely from a computer screen being operated in the
studio.
--
=Barry Wainwright=
"Well-timed silence hath more eloquence than speech." Martin Farquhar Tupper
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