TV Detector Vans

Hi,

I was thinking about TV detector vans, didn't they use to work by picking up
the signals from the scan coils in CRTs? (Tell me if I am wrong)
Are they not finding it very difficult these days to 'detect' LCD / Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

Nige

Nigel Percy wrote:
Hi,

I was thinking about TV detector vans, didn't they use to work by picking up
the signals from the scan coils in CRTs? (Tell me if I am wrong)

No, it's the local oscillator in the tuner section that is apparently
received, so the display device (or even lack of one) is not a factor.

Are they not finding it very difficult these days to 'detect' LCD / Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

There's a thread currently raging in uk.media.misc.tv discussing just how
feasible/possible the detection is these days.

--
Mark
Please replace invalid and invalid with gmx and net to reply.

Nigel Percy wrote:

Hi,

I was thinking about TV detector vans, didn't they use to work by picking up
the signals from the scan coils in CRTs? (Tell me if I am wrong)
Are they not finding it very difficult these days to 'detect' LCD / Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

Nige

Don't they now just harrass folks who don't have a license? I think
even more so if they have had one and stopped having one. Just take a
look at this little blog

http://blogs.warwick.ac.uk/davidmetc...censing_leave/

and another

http://www.denyerec.co.uk/index.php?p=111

and there are probably many more, aswell as this interesting guardian
item

http://www.guardian.co.uk/guardian_j...566287,00.html



--
Paul (Neurotic to the bone No doubt about it)
------------------------------------------------------
Stop and Look
http://www.geocities.com/dreamst8me/

"Mark Carver" wrote in message
...
Nigel Percy wrote:
Hi,

I was thinking about TV detector vans, didn't they use to work by picking
up
the signals from the scan coils in CRTs? (Tell me if I am wrong)

No, it's the local oscillator in the tuner section that is apparently
received, so the display device (or even lack of one) is not a factor.

Are they not finding it very difficult these days to 'detect' LCD /
Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

There's a thread currently raging in uk.media.misc.tv discussing just how
feasible/possible the detection is these days.

--

Well it is many years ago now but one evening there was one of the vans in
the supermarket carpark, guess the men have to buy food sometime, and the
back door was open. Guess what, nothing inside.
So I guess they use vans clearly marked TV Detector and have a list of
houses which have no recorded TV lience purchase and drive down that street,
and enquire at that house.
I have noted from time to time advance warning of the van being in an area
in the local newspaper.
I think these things scare people into buying a lience.

--
Regards,
David

Please reply to News Group

I was thinking about TV detector vans, didn't they use to work by
picking up the signals from the scan coils in CRTs? (Tell me if I am
wrong)
Are they not finding it very difficult these days to 'detect' LCD /
Plasma screens? What about a PC with a freeview card recording to the
hard disk and then watching the MPEG later, that must be very
difficult to detect.

The vans are old hat now but they do exist. They also have handheld
detectors. They detect RF signals form the local oscillator in the tuner.

Peter Crosland

The message
from Mark Carver contains these words:

Nigel Percy wrote:
Hi,

I was thinking about TV detector vans, didn't they use to work by
picking up
the signals from the scan coils in CRTs? (Tell me if I am wrong)

No, it's the local oscillator in the tuner section that is apparently
received, so the display device (or even lack of one) is not a factor.

Are they not finding it very difficult these days to 'detect' LCD / Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

There's a thread currently raging in uk.media.misc.tv discussing just how
feasible/possible the detection is these days.

Yes the LO radiation was quite strong enough for the TV detector vans
to pinpoint the actual room the TV set was located in since the bulk of
said radiation was emitted from the chassis (or PCB) rather than the
antenna feeder.

The TV detectors could also figure out which channel the set was tuned
to since the LO was offset below the channel by the common IF of (ISTR,
35MHz, but feel free to correct me on this.)

To successfully suppress such unwanted radiation requires screened
boxes within screened boxes with all feeds (power, IF output etc)heavily
filtered. Such filtering needs to be very carefully designed for it to
be sufficiently effective to endow the reciever with stealth capability.
It can be done but it's a very expensive exercise for commercial
production.

However, that's not to say such an exercise in modding a TV set is
beyond the abilities of a talented (and motivated! :-) amateur, provided
he's got access to suitable test gear to verify the efficacy of his
efforts.

Of course an alternative to 'stealthing' the LO is to suppress the TV
detector van's recievers by swamping them with an edge of band signal
(in this case around the 430MHz mark give or take whatever MHz it might
require to avoid detection by existing services that might actually give
a ****).

Since the range between your swamping transmitter and the 'enemy' is
unlikely to exceed 100 feet, I doubt you'd need more than 1 watt of Tx
Power for the job, especially as you'd be using a directional antenna to
focus your signal into the roadway to maximise benefit whilst minimising
co-lateral damage to your own and to your neighbours' TV reception.

The drawback to this is that the TV detector operatives might be savvy
enough to recognise the effect and call on other services to pinpoint
the source of the swamping signal. As a method, it could only look
attractive when there's a house full of TV sets to hide. :-)

On second thoughts, I'd opt for the 'Russian Dolls' screening boxes
arrangement. Probably set up a suitable Multimedia PC within it's own
custom built screened box in the basement (if you have one) and stream
the content over fast or Gb ethernet to suitably located PC based
viewing stations.

You might think that a PC based TV reciever might have sufficient
screening seeing that the tuner module is fitted within the confines of
a metal case designed to meet the EEC directive on EMC, but I wouldn't
place any reliance on the effectiveness of this without a searching and
thorough test with suitable test gear.

It's amazing how difficult it can be to confine unwanted radiation
products within a screened box without benefit of suitable absorption
materials or devices being placed inside said screening box.

A plain screening box without absorption materials inside can become
very ineffective if there's the slightest gap to allow the radiation to
escape. Field strenghs will rapidly build up inside until equilibrium is
reached with any one wave being reflected maybe a thousand times or more
before it's attenuated to insignificance

One thing in favour of the PCI tuning cards is that the screening tends
to be much better than in a TV chassis simply to minimise interference
from the shedloads of digital hash that exists within any modern PC.
Since screening work both ways, that makes a PC based solution a more
viable option than modding an existing TV reciever.

Of course, anyone contemplating such measures needs to remember to
stealth the antenna (and its feeder) as well! :-)

HTH

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

In article ,
David wrote:

--

Well it is many years ago now but one evening there was one of the vans
in the supermarket carpark, guess the men have to buy food sometime, and
the back door was open. Guess what, nothing inside.

But some detector equipment is small enough to be hand portable. pehaps
they'd gone with it to check on something local.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

Ohh, not 'TV Detector Vans' again!

Pay for the BBC from a hypothocated sum raised by general taxation and then
let the 50 people without a TV claim a rebate. So simple!

While we're at it, let's remove car tax and put it all on fuel. I can't see
why my dad should pay a full road fund when he only does about 35 miles per
year (that's his mileage, not his speed).

Bill

The message
from "Bill Wright" contains these words:


Ohh, not 'TV Detector Vans' again!

Pay for the BBC from a hypothocated sum raised by general taxation and then
let the 50 people without a TV claim a rebate. So simple!

While we're at it, let's remove car tax and put it all on fuel. I can't see
why my dad should pay a full road fund when he only does about 35 miles per
year (that's his mileage, not his speed).

Mind you, that could still be described as an average speed (35mpy :-)

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

"Nigel Percy" wrote in message
...
Hi,

I was thinking about TV detector vans, didn't they use to work by picking
up
the signals from the scan coils in CRTs? (Tell me if I am wrong)
Are they not finding it very difficult these days to 'detect' LCD / Plasma
screens? What about a PC with a freeview card recording to the hard disk
and then watching the MPEG later, that must be very difficult to detect.

Just wondering...

I really don't think they need to bother as its a resonable assumption that
every residence
has at least one TV.
An aerial or a sattellite dish is a big clue too!!!!