Jinx <joecolquitt <at> clear.net.nz> writes:
> > Not to go too far OT, but, do they really do this in the UK?  License 

They used to do it for sure (to be read in : R.V. Jones, Most Secret War - where
H.M. 'Services' applied communist spy radio transmitter hunting vans to the
location of local leftists who treated the BBC's TV transmissions as public
property).

Worse, I caught some strange happenings myself, while monitoring off air signal
quality a few years ago, when at the start of the evening news the sound
subcarrier shifted firmly about 50kHz over about 2 seconds (this is inaudible,
and excludes a hard switch to a different modulator). After the news the carrier
shifted back, equally slowly. Anybody monitoring field strength at 5.5MHz and
5.550 MHz (or 5.450) would have had an instant percentual reading of the
percentage of news program tuned sets. Similar games have been seen played with
the RF carrier proper, for similar purposes. This works both for radio and TV
(both off the air).

Now with cable the question is moot. The cable boxes call home and tell the
operators what people are watching, when, and when they are zapping. There is no
way around it since the local digital distribution box MUST receive a select
signal to send the relevant data down the subscriber lines. The subscriber lines
no longer have the bandwidth to carry all the selected programs on the 'last 100
feet'. Rough calculations show that a high quality provider would need at least
1.5GHz of bandwidth on the last 100 feet to put 200 programs through. That does
not happen, however the fiber or the backbone that feeds the local distribution
boxes does have that kind of bandwidth. Typically a local distribution box is
shared between 2-30 subscribers. The actual numbers vary with the provider and
the system.

Peter P.


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