They were a real thing. When an old style TV amplifies the TV signal and feeds it to the CRT tube, it leaks a lot of the boosted signal. I think the rumour that the vans were a fake was probably because they only ever had a few and it was mostly a propaganda show, but that doesn't mean they didn't exist.
Intelligence agencies used receivers to snoop in on CRT computer monitor signals and could re-generate the display output, I remember watching a TV program where some electrical engineers built a home-grown version and demonstrated how it worked. It was only effective up to about a dozen metres IIRC with their setup, but theoretically could work at longer range with better hardware.
I remember chatting with friends about it because we were playing an espionage RPG at the time so of course we wanted our characters to have access to the tech.
They were fake. It would be extremely difficult on most streets and impossible in virtually all tower blocks to triangulate an exact location to a single house/flat.
And the design was ridiculous. A working detector doesn't need to look anything like an aerial stuck on top of a minivan.
And the only record of them being used in a prosecution is for optical detection of combined RGB. Plus some handwaving. Not RF.
So they were pretty much a psy-op.
It's relevant that the license fee collectors - who belong to Capita, one of those curious quasi-private-with-state-support companies that buzz around the British government like flies - rely almost entirely on self-incrimination for prosecutions.
Thank you. Just last year or so there was an article linked on HN that investigated on this. And it turned out to be all fake. There was some sort of prototype that actually worked, but the range was so limited and localization was not possible at all ... it simply wasn't practical for any use. As the funding was somewhat public and news picked up on that, the myth was spreading and they made these fake vans with scary antennas and went on their scare-/psy-ops. News picked up on that again and word quickly spread all around. IIRC there was even some exhibit linked in the article that had various builds of these fake-vans. Of course everything was only props. The real deal simply only existed in people's heads. Plus there isn't any working hardware from that era to be found nowadays anywhere anyway. As the conspiracy theory goes on, that's apparently because it was all destroyed by BBC after the act. If you ask those people about all the other countries that had this apparently going on about where the remains of the equipment are nowadays you get a ¯\_(ツ)_/¯ at best.
So the linked articles in actual post office electrical engineering journals from the time, over several decades, including detailed calculations and implementation details were also fake?
Plus they managed to somehow infiltrate a fake freedom of information request detailing a BBC application for a warrant based on TV detection, and internal documents detailing the operation of the relevant department and its legal basis of operation, into the whatdotheyknow FOI requests archive?
It seems unlikely, especially for varied forms of evidence over such a long period.
>> When an old style TV amplifies the TV signal and feeds it to the CRT tube, it leaks a lot of the boosted signal. I think the rumour that the vans were a fake was probably because they only ever had a few and it was mostly a propaganda show, but that doesn't mean they didn't exist.
Just because the technology exists, doesn't mean the BBC actually used it. For one thing, it would have been far cheaper to put out the word that the vans are on the streets and patrolling, than to actually buy them, equip them and staff them with trained personel that could operate the devices.
Alternatively, perhaps a few of those vans really did exist and the rest was smoke and mirrors- rumours, fake vans without any active technology, etc.
Note that the reason I'm finding this likely is that the TV Licensing people are known for using psychological warfare tactics. For instance, I don't watch TV [1] and yet I periodically receive threatening letters from the TV licensing authority telling me that if I'm found to watch TV without a license I'll be fined, etc. Clearly, they send those letters to all addresses in the UK that don't have a license, under the assumption that most addresses without a license actually need one and that by sending out threatening letters en masse they will scare some of those shirkers into compliance- regardless of how many people who don't actually watch TV they end up threatening in the process. I've also seen some really startling public campaigns with posters showing bullseyes on houses, creepy slogans about being watched and so on.
Their tactics are a veritable nuisance and their mass mailing campaigns may or may not have the effect they want, but they sure have the effect of bothering random, uninvolved people with threatening government spam.
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[1] Er, well. I do occasionally watch TV shows, or rather clips thereof- on youtube. But that's not covered by the licensing. You need a license if you're watching TV programmes as they are being broadcast. So for example, I had a TV set for a few years that I used exclusively with a PS2 and I didn't need a license for it- but I'm pretty sure that if I had ever been visited by one of the TV licensing agents, I'd have been forced to pay anyway. How exactly do you prove that you have a TV set but don't watch TV? Most modern houses have aerial plugs - mine sure does. The only thing that really stopped me from connecting the TV set I had to the aerial was that I basically dislike TV. How do you prove that to an agent hell-bent on collecting?
I used to get the letters because I bought a TV for use as a monitor for video projects and I was stupid enough to give my address when asked to.
They're sent out on a cycle with a bit of randomness. It's quite fun to collect the set.
They stopped when I phoned the Bristol office and they asked how I'd feel if an inspector came over. I told them they were welcome any time, and the drive over would be a nice day out. [True]
I'm sure it's entirely feasible to build such a thing, but try to find a case prosecuted because of a detector van, or results used as evidence. It doesn't appear to have ever happened.
And where is the detector van union? Memorial service for the driver who crashed? Job postings?
The solution built in R&D (as far as the rumour goes) was much simpler. There were only a few channels (typically 4) and this would have been all analog broadcast. The much simpler signal that TVs "leak" is light.
So look at the pattern of changing colours through curtains, and compare to a TV in the van with something to diffuse the light over the top.
Of course, the even simpler approach is to tell people you can do this and just send around / threaten to send around random vans.
when i read that article years ago i went in to a huge rabbit hole about side-channel attacks. A lot of the information from that reading spree has stuck with me
Yeah, this reminded me of the dutch broadcastings association 1969's april fools joke. In which they said to have developed a device that detects "zwartkijkers" (blackwatchers), for use by mailmen [1].
Funny detail, the reporter asked "Can this devise detect all televisions?" to which the fake interviewee answered, "well if you wrap your set in aluminum foil no, but otherwise yes". The next day aluminum foil was sold out nation-wide.
I've done some work with Buckman Hardy in the UK, they developed and sold a handheld detector to the BBC. They're a legitimate engineering company, I doubt they would admit to being in on the gag if this was fake.
I don’t believe there has been a single conviction based upon evidence gathered by these vans. They’re like lie detector machines - useful only as a tool to get people to confess. Same with the inspectors, they’re private citizens with no legal authority to enter a property without permission. Their purpose is to cultivate fear of prosecution, not to recoup lost revenue.
> I don’t believe there has been a single conviction based upon evidence gathered by these vans
According to the article they were not intended for convictions but instead to get a search warrant and then gather evidence for a conviction.
So who knows how many convictions were started because of the vans. Though I agree that the fear factor probably did help more than the search warrants.
I believe the current theory is they simply look for light leakage. If they see a "flash - 200ms - flash - 400ms - flash - 350ms - flash" pattern leaking through your curtains precisely at the moment the same pattern occurs in a live broadcast they know you're watching.
There was another theory (spread by the media and by the half-denying-half-encouraging bbc) that the vans can detect iPlayer usage across WiFi by looking at the level of network traffic, and then to a range of IP addresses in an area intentionally changing the amount of data the app received up/down to see if network activity changed correspondingly.
It’s really all a big scare tactic though. The best way to detect iPlayer being used wrongly will be to see who registers for an account with an identifiable email address.
You say simply, but I think that's much more difficult than just detecting the presence of em noise conforming to a broadcast standard.
Anyone that's put an AM radio next to a CRT TV knows it emits em noise.
The CRT itself is, to over simplify, a high voltage capacitor. It's one of the most popular devices used to power hobbyist Tesla coils...
I don't know why everyone seems to think that just because TVs were "receive-only" devices, that they wouldn't emit any sort of easily detectable signal.
Also, when this enforcement began, broadcast was the only source of TV content, so the presence of a TV was generally proof of watching broadcasts. There wasn't really any need to prove the TV was tuned to any particular content.
Now, whether it is a practical, effective method of enforcement that was actually used is another matter.
Maybe poor phrasing on my part, but that's the prevalent theory I've seen for how they do it today. Various other methods of EM leakage might have worked in the past (unproven as far as I know), but modern televisions are so much better built that visible light leakage is believed to be the only effective detection method.
Here's my TV detection method: look at their windows and see if there's a light flickering pattern that looks like a TV (if behind curtains) or maybe you can see the TV
Yeah I thought it was just a scare tactic and something the licence 'enforcers' could say (i.e. 'our detector van says you have a tv') to try and catch people out.
They surely can't get too much of a return paying people to check up on only potential licence 'evaders' so investing in a fleet of actual vans with drivers and operators would further reduce any return.
Many but not all :) - Some buddies of mine used to live in a student flat in Bristol that overlooked the TV Licensing Authority offices. My friends watched them go about their business over the top of their unlicensed TV for 2.5 years.
I remember as recently as the mid 90s there were intimidating advertisements on UK tv about how tv license vans were going to find you and kick your doors down if you hadn't paid.
I had assumed it was complete scare tactics, I never once thought that they had existed in some previous era.
The technology is completely sound, MI5 invented the rough idea for hunting spies (Operation RAFTER), but whether it was widespread or not? Seems unlikely.
The idea of a van watching you is enough for many to change their behavior