Author Topic: For the countries which need Radio and TV licenses. How TV Detector Vans work...  (Read 11997 times)

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Offline pdenisowski

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That worked for very old tvs (Unshielded wooden box full of radiating wires), I doubt they can sense and LO or IF frequencies in modern tvs.

Oh, with the right equipment you absolutely can detect (and DF) an LO from a significant distance away - I've personally done this many times. 

It's also not an uncommon application:  how do you think police catch people illegally using radar detectors? :)
« Last Edit: January 08, 2025, 08:51:56 pm by pdenisowski »
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Offline pdenisowski

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To me, this falls in the same category as "yepper, them satellites can read your license plate from space!" misconceptions.

I was told that they used hundreds of vans that drove around with equipment that could monitor the IF frequency of people's TVs and from the frequency they could tell what channel you were watching. 

this is approaching tinfoil-hat territory.

I'm fairly certain it's never been applied to TV licensing or viewership studies, but it absolutely is possible to see what someone is watching from outside of their home - just use a TEMPEST receiver  :)



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Offline Postal2

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I'm fairly certain it's never been applied to TV licensing or viewership studies, but it absolutely is possible to see what someone is watching from outside of their home - just use a TEMPEST receiver  :)
I wondered who this swindling trick was aimed at. Clearly not the specialist. That means his boss. We elect as bosses those idiots who cannot do useful work.

This can be clearly seen in the history of Space Shuttle Challenger.
« Last Edit: January 08, 2025, 05:08:31 pm by Postal2 »
 

Offline TimFox

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Some confusion here:  there can be enough radiated power from a local oscillator (LO) in a superheterodyne receiver to be detectable with appropriate equipment nearby, but the power in the intermediate-frequency (IF) amplifiers is not likely to radiate.

A typical double-balanced mixer, driven by +7 dBm into the LO port, has 50 dB isolation from LO port to RF (input) port.  That's -43 dBm leakage (50 nW), but there is more power circulating in the oscillator itself.
The CRT TV sets of my youth were not particularly well-shielded, usually in a plastic housing.  Also, the input mixer was not double-balanced.

Radar detectors use simple diode mixers from their receiving antenna, driven by a suitable local oscillator, where the isolation is much worse.

TEMPEST is an interesting concept.  Modern equipment must pass emissions testing to avoid interference with other systems, but TEMPEST is a tighter security specification for when the emissions might contain information of strategic value.
When I first read of it, one had to show a need-to-know to find the actual specification, and ones supervisor could not access the specification unless he showed his need-to-know.
« Last Edit: January 08, 2025, 05:36:10 pm by TimFox »
 
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Offline coppice

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TEMPEST is an interesting concept.  Modern equipment must pass emissions testing to avoid interference with other systems, but TEMPEST is a tighter security specification for when the emissions might contain information of strategic value.
When I first read of it, one had to show a need-to-know to find the actual specification, and ones supervisor could not access the specification unless he showed his need-to-know.
That's true of most defence related specifications. The basics of TEMPEST are not classified, as the basics are just screen, screen, screen. The details are classified.
 

Offline coppice

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I'm fairly certain it's never been applied to TV licensing or viewership studies, but it absolutely is possible to see what someone is watching from outside of their home - just use a TEMPEST receiver  :)
Maybe they could start using it to detect people watching BBC TV from https://www.bbc.co.uk/iplayer

I first saw a demonstration of remote viewing of a raster scan image in the 1980s, when we were first required to get serious about TEMPEST compliance. That was with a CRT, and I think the receiver was picking up radiation from the tube itself. What are they picking up strongly enough to reconstruct the raster from an LCD display?
 

Online tom66

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I really doubt TEMPEST can work with modern LVDS signals as used inside LCD/OLED TVs - there simply isn't going to be enough radiated information there, and the encoding will be 8b10b or similar which means that a single incorrectly received bit makes the decoded codeword completely wrong (and creates no obvious difference between full white and full black data).  You could make it work with VGA and/or CRT monitors because the analog signal provides just enough information to distinguish text and items on a computer monitor.
 

Offline Postal2

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I really doubt TEMPEST can work with modern LVDS signals ....
It can work. With a specially selected picture and a specially selected laptop, at a distance of about one meter.

...I first saw a demonstration of remote viewing of a raster scan image in the 1980s, ....
This was done by an optical sensor from a remote CRT, which has low afterglow.
« Last Edit: January 08, 2025, 07:01:28 pm by Postal2 »
 
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Offline coppice

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I really doubt TEMPEST can work with modern LVDS signals as used inside LCD/OLED TVs
TEMPEST is actually a specification for securing sensitive information. It involves Faraday cages, product screening and other measures. The TEMPEST receiver is a test set to verify that the screening is adequate to meet the residual emissions requirements.
 

Offline coppercone2

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Its also designed to be future proofed for cold war paranoia, so just in case someone managed to get 20db lower noise on a new wonder weapon receiver you don't have to rebuild all your 'security infrastructure'

I think now the real problem is 'add on software' , not sure if anyone would seriously consider more tempest instead of making a better worm?

It seems like a pretty scifi concept, compared to a computer virus, which is well proven, makes alot of money each year, basically impossible to trace (though now you can probobly get some 'AI signature' possibly showing what they used to make more advanced ones) etc

BTW for radar detectors, that is usually a directional horn antenna. that really focuses the power down.

TV I don't know. FM radio, it seems that most would be just a rod antenna that is omnidirectional.
« Last Edit: January 08, 2025, 07:13:42 pm by coppercone2 »
 

Offline coppice

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Its also designed to be future proofed for cold war paranoia, so just in case someone managed to get 20db lower noise on a new wonder weapon receiver you don't have to rebuild all your 'security infrastructure'
It wasn't paranoia. A lot of interesting tricks have been used to extract information from opponents, and its not specifically a cold war issue. Practically all governments spy on anyone they can get away with all the time. The FVEY program may look like five buddy buddy countries, but you can be sure each of those five is endlessly spying on the other four.
 

Offline coppercone2

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The only 'good' one I heard of was the underwater spy bug the CIA made that clips onto fiber optics.

It seems like usually the NSA is doing things with code more then anything else.


Maybe its different in highly classified areas like space, it seems like the only place you can get giant ass complicated radios next to something important with impunity and some black paint


and probably embassies, no one ever gives out info about those
« Last Edit: January 08, 2025, 07:19:29 pm by coppercone2 »
 

Offline TimFox

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Sanitized CIA report:  https://www.cia.gov/readingroom/docs/CIA-RDP90-00965R000100310007-3.pdf
This underwater caper involved putting a sensor near an underwater cable on the sea floor, near Kamchatka.
The Soviets would periodically pull the cable up to check for damage or penetration, to no avail, until the cover was blown by treachery.
https://interestingengineering.com/innovation/operation-ivy-bells-the-us-top-secret-program-that-wiretapped-a-soviet-undersea-cable
 

Online valcher

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What amazing stories I learned from you, in the Soviet Union there were never any licenses for radio and television. Yes, we had few TV channels and they were all state-owned, many programs were aimed at praising communism, but there were also educational, entertaining, cultural, educational, and educational programs. We only paid for the use of a collective antenna in apartment buildings, and in private homes we installed our own antennas. Probably, some part of the money was included in the cost of televisions and radio receivers, but if you assembled your own television or receiver, no one demanded anything from you.
Now, in the era of the Internet, everything has changed, terrestrial television has not yet died, but radio stations remain mainly only on the FM range.
 

Online Zero999

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as you were required to license any device which you held at your property that could act as a television receiver, regardless of whether you were actually using it as such.
not quite, regardless of what the propaganda would have you believe.it was the act of receiving the broadcast that required a license,complete with quirks like needing a colour license if you had a black+white telly and a colour video recorder.However if the telly  was only used for example to watch  videos or hooked up to yer zx81  no license  needed.

Happened to me. I used a B&W portable to play with my ZX81 but also to view TV. Got a knock on the door one day and it's the TV Licensing people, and it just so happened that I'd been doing some programming on the dining room table, so the antenna wasn't plugged in (didn't reach). They took a look and were happy that the TV wasn't used for watching programmes  :phew:
The make spot checks. It was most likely a coincidence. I've had a note through the door, which was a form, filled out by the licence inspector telling me they've called and will visit again, even though I wasn't there at the time and didn't have a TV switched on.

Don't worry. You have no legal obligation to allow them into your property or even speak to them. The correct response would have been to simply say no and close the door.
TV detector vans don't work in the UK (and I doubt they ever did).  They are purely a marketing ploy by Capita (the contractor) and the BBC.
That's true. I suspect that, even it was possible to detect an analogue TV, it was simply impractical to do so in populated areas and it's not worth their time to visit sparsely populated places.

Quote
I think the BBC will need to reform how the licence fee is collected as currently any terrestrial consumer of content pays a licence fee (even if they do not watch BBC services) but no consumer of streaming content does; fundamentally what is the difference here?
They should just make a subscription service, like any other.

I think it's important to have some form of public broadcaster, for news and current affairs documentaries and such. 
Why?

That was never the case before TV and radio. You didn't pay a for a licence/tax to buy a newspaper/magazine, so you can receive a government newspaper.

The idea seems somewhat bizarre to me. All that's happens is the public broadcaster favours whatever political party is in favour of investing more. Any party who wants to cut back, will receive more bad press. To be fair this somewhat affects all radio and TV stations, due to how the RF spectrum is licenced, but it's not so strong.
 

Offline coppice

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TV detector vans don't work in the UK (and I doubt they ever did).  They are purely a marketing ploy by Capita (the contractor) and the BBC.
I expect you are right about the current situation. However, a friend saw one working in the late 70s, and described it to me. Typical residential streets scanned OK, but flats defeated them. TVs were a lot less sophisticated then, and signals leaked like a sieve. These days, with an emphasis on EMI/EMC, things are very different. The signals they can look for are also very different, and a lot more diverse.
 

Offline BrianHGTopic starter

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For those who didn't realize, older TV and radios LO oscillator was mixed with the antenna signal coming in and it also literally leaked and radiated out through the same antenna the TVs and radios used to receive their broadcasts.

Yes, you can see each LO on these TV prior to the mid 90s with ease by a few houses in each direction.

When sniffing with a directional antenna and spectrum analyzer, you can easily narrow down to every 1 to 2 houses.

Everyone who says this is impossible never played with this equipment in the 70s and 80s.  The signals are there visualized in spikes on the cheap analog RF spectrum analyzers of the time and the changes in their amplitude is easily seen on said spectrum analyzers of the time just by rotating your directional antenna.

« Last Edit: January 08, 2025, 09:54:11 pm by BrianHG »
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Online Zero999

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TV detector vans don't work in the UK (and I doubt they ever did).  They are purely a marketing ploy by Capita (the contractor) and the BBC.
I expect you are right about the current situation. However, a friend saw one working in the late 70s, and described it to me. Typical residential streets scanned OK, but flats defeated them. TVs were a lot less sophisticated then, and signals leaked like a sieve. These days, with an emphasis on EMI/EMC, things are very different. The signals they can look for are also very different, and a lot more diverse.
If they were a thing then why can't I find any cases when evidence from TV detector vans have been used?
« Last Edit: January 08, 2025, 11:00:53 pm by Zero999 »
 

Offline SteveThackery

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A few years ago a public information film was broadcast on the TV here in the UK. It was very brief and to the point:

"A list of all the addresses without a TV licence. That's all we need."

I think it was addressing the (correct) growing awareness that digital services had rendered the old vans ineffective.
 

Offline Postal2

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... why can't I find any cases when evidence from TV detector vans have been used?
The license violators were tortured and were unable to tell anything.
 

Online Zero999

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... why can't I find any cases when evidence from TV detector vans have been used?
The license violators were tortured and were unable to tell anything.
Court records of course.
A few years ago a public information film was broadcast on the TV here in the UK. It was very brief and to the point:

"A list of all the addresses without a TV licence. That's all we need."

I think it was addressing the (correct) growing awareness that digital services had rendered the old vans ineffective.
Which is a load of bollocks because just because an address is unlicensed, it doesn't mean it requires one. It's equivalent to saying "A list of people without driving licences."
 

Offline Analog Kid

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TV detector vans don't work in the UK (and I doubt they ever did).  They are purely a marketing ploy by Capita (the contractor) and the BBC.

There's a very simple way that the TV Licencing people know to write to you, because every time you buy a new TV the retailer is required to notify your address to the authority. 

But, owning a TV in and of itself doesn't require a licence; we do not consume BBC content any more and have gone licence free for some time. 

I think the BBC will need to reform how the licence fee is collected as currently any terrestrial consumer of content pays a licence fee (even if they do not watch BBC services) but no consumer of streaming content does; fundamentally what is the difference here?

I don't get it, perhaps due to my ignorance of the situation over there.
Do people get BBC content over the air? If so, that would explain things; no way for them to really know whether you're consuming their programming or not.

But if it's over cable, then wouldn't it work the same as here in the US where you get billed for a cable connection, and the connection goes dead if you don't pay?
 

Online langwadt

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... why can't I find any cases when evidence from TV detector vans have been used?
The license violators were tortured and were unable to tell anything.
Court records of course.
A few years ago a public information film was broadcast on the TV here in the UK. It was very brief and to the point:

"A list of all the addresses without a TV licence. That's all we need."

I think it was addressing the (correct) growing awareness that digital services had rendered the old vans ineffective.
Which is a load of bollocks because just because an address is unlicensed, it doesn't mean it requires one. It's equivalent to saying "A list of people without driving licences."

if a TV means you require a license what microscopic fraction of households doesn't need one?
 

Online langwadt

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A few years ago a public information film was broadcast on the TV here in the UK. It was very brief and to the point:

"A list of all the addresses without a TV licence. That's all we need."

I think it was addressing the (correct) growing awareness that digital services had rendered the old vans ineffective.

the vans have been pointless for half a century, why bother with detecting when +99% of households have a TV? just visit the few that pretend they don't have one
 

Offline TimFox

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[quote author=Analog Kid link=topic=449663.msg5776183#msg5776183 date=1736378824

I don't get it, perhaps due to my ignorance of the situation over there.
Do people get BBC content over the air? If so, that would explain things; no way for them to really know whether you're consuming their programming or not.

But if it's over cable, then wouldn't it work the same as here in the US where you get billed for a cable connection, and the connection goes dead if you don't pay?
[/quote]

In some countries outside of the USA, the funding mechanism for national broadcasting is a license fee on receivers.  Here, the discussion is mainly about the BBC in the UK.  Another example is Japan’s NHK, who employ door-to-door collection agents.  Any compulsory payment scheme is bound to be controversial in that country.

The Museum of Broadcast Communications in Chicago reports that two-thirds of countries in Europe and half of countries in Asia and Africa use television licences to fund public television. Television licensing is rare in the Americas.
« Last Edit: January 08, 2025, 11:59:34 pm by TimFox »
 


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