TV Detector Vans
 

I vaguely remember seeing photographs of TV detector vans back in the day of 405 line telly and if I recall correctly they were Commer vans - the ones with sliding front doors - with a couple of long conical horn type constructions bolted onto the roof.

There's a lot of myth surrounding them. Did anyone ever see one or even work in one?

Re: TV Detector Vans
 

Never worked one but remember them.
Do they still have them today?
I was hounded recently by the licensing authorities, I think they need some decent address/merge software in their IT systems!

Cheers.

Re: TV Detector Vans
 

See here:

http://www.autoblog.com/2008/06/09/a...detector-vans/

Neil

Re: TV Detector Vans
 

Only one, and it was in the early 80s when they were doing a licence purge in the area. it looked really ancient.

I read in a newspaper that these days they don't have them because the gear has grown smaller with the rest of electronics and the inspectors have hand held TV detectors.

They may have just about worked, but I'm sure most enforcement is down to paper work, psychology and people confessing. I'm not sure that they ever successfully prosecuted anyone on the basis of detector van evidence alone.

Pete.

Re: TV Detector Vans
 

Did they ever actually 'detect' anything? Was it all just a scare factor and in fact the vans contained nothing that actually did anything? I know it was possible to detect timebase noise but it's doubtfull if you could actually determine which channel someone was tuned to.


SB

Re: TV Detector Vans
 

Mainly kidology I'd have thought.

Pete.

Re: TV Detector Vans
 

The journal of "The Institute Of Post Office Electrical Engineers" (IPOEE) certainly featured articles describing the equipment in the vans and how it worked. A portable detector was used in blocks of flats. The Post Office Gazette also ran adverts for staff to do a stint manning the vans. Applicants had to have a driving licence, be able to demonstrate the equipment to the media and be prepared to give evidence in court. The vans were regularly parked in local Telephone Engineering Centres (TECs) during the day and ventured out in the evenings at peak viewing times.

It could have been an elaborate hoax, but I doubt it.

Re: TV Detector Vans
 

Quote, Sideband: "I know it was possible to detect timebase noise but it's doubtfull if you could actually determine which channel someone was tuned to".

I'm not so sure about that, SB. :-/

The local osc. will almost certainly radiate some of its signal from the aerial - albeit at a significantly reduced level, but enough for a sensitive receiver to find it and then do the necessary D.F.
In a parallel vein, at about the period in question, when I used my Eddystone 888A receiver on 10 metres with a 110' 'longwire', it used to completely block out TV reception downstairs - much to the annoyance of my parents - and the TV received field strength was substantial - you could see the TV TX mast on the nearby hill from the lounge window!

Morever, the technique of 'electronics evesdropping' (and its prevention) has been used for many years by various Government Security Agencies: look up 'Tempest' on the 'Net: same principles are involved.

Al.

Re: TV Detector Vans
 

I was told that the detector van would turn up at an estate somewhere and invite all the kiddies inside and show them how it worked. The kiddies would go home and tell their parents and the next day there would be a queue outside the post office of people wanting to buy a TV licence.

Re: TV Detector Vans
 

There was a long thread on here about TV detector vans a year or so ago. It was inconclusive, but which I mean people were not convinced for or against the idea that the vans actually worked as described. Not much point in repeating it.

Re: TV Detector Vans
 

See:-

http://www.britishtelephones.com/veh...htvans/023.htm

There was a discussion about this in this thread last year from post # 64 :-

https://www.vintage-radio.net/forum/...tor+van&page=2

Some were real but a lot were fakes.

Regards, Mick.

Re: TV Detector Vans
 

Of course, if you knew what IF the detector vans used (I'm presuming, not unreasonably, that they were superhets) you could, with a sensitive enough receiver, build a TV detector van detector; which would pick up the detector van's local oscillator and automatically switch off the TV as soon as a TV detector van was detected .....

Having a free choice of IF, you'd not be quite so vulnerable to a TV detector van detector detector!

Why wasn't a smartcard reader mandated for all digital receivers, whether combined or separate, from the outset? Then the BBC could have just issued viewing cards for their programmes, and had automatic licence fee enforcement with no need for heavy-handed tactics.

Re: TV Detector Vans
 

When colour arrived,it was the 4.43Mhz Oscillator that was detected and of course it cost much more for the licence.

David

Re: TV Detector Vans
 

Indeed, AJS: ECM (electronic counter-measures) & ECCM (electronic counter-counter measures) are at the core of your suggestions, re-your paras. 1 and 2. And in certain, well-guarded corridors of power, the associated technology & its implementations are kept well under wraps. I can say no more.

Al. / Skywave.

Re: TV Detector Vans
 

In which case, detecting the local oscillator radiation - and thus deducing what channel the set was tuned to - would also have been possible.

Al.

Re: TV Detector Vans
 

Is anyone in possesion or restoring any of the tv detector stuff?
I guess TV detection will be a thing of the past soon.

Cheers

Re: TV Detector Vans
 

It would be great for a Forum member to find and restore an old detector van! Not much chance though, I bet...

How? I thought that by the time colour TV arrived, both the BBC and ITV timebases and colour subcarriers were so accurately generated that you couldn't distinguish between them

Re: TV Detector Vans
 

Wouldn't the identification offset used by stations show up on the line timebase? It is this which causes two seperate but locked pictures to be seen if received together (??)

Re: TV Detector Vans
 

The 4.43 was picked up to determine that there was a set running and if the location didnt have a licence then i guess there was a loud knock on the door.

David

Re: TV Detector Vans
 

The only known Commer TV detector van to survive has been restored:-

http://www.***********/photos/29485695@N02/5666139441/

Took about 6 years:-

http://66.129.69.181/forum/topic.asp...8&whichpage=20

Regards, Mick.

Re: TV Detector Vans
 

That wouldn't work David. Some Sony sets never used a 4.43 Xtal

Re: TV Detector Vans
 

They definately detected the line timebase radiation. Back in the 60's I used to do service calls in the evenings. The car radio was usually tuned to the Light Programme, Radio Two on Long Wave. As you drove down the street the whistle could be clearly heard and in some cases it completely blanked out the radio signal. It was very directional and you could pin point the house easily. A directional transistor radio would have been even more reliable. Regards, John.

Re: TV Detector Vans
 

Many years ago when proper Tellies were still the norm we did ponder...

Because the Line timebase was probably the easiest to detect, and given the poor regulation of many circuits at the time, whether the technology of the detectors might possibly be able to reconstruct something approaching the actual image being viewed..?

Re: TV Detector Vans
 

Thats intresting Dave re some Sony.So how did they get around that?Seem to remember changing Orange Trimmer and Xtals for int colour faults on Sony 5 years ago.

David

Re: TV Detector Vans
 

Detecting the timebase was the easiest way back when we had two channels on 405. the sync from the radiated timebase was displayed on a scope and compared with the off air syncs the one that "fitted" was the channel being watched.
The dual standard years 64-69 was easy too as we only had BBC2 on 625. Most early colour sets radiated line blazes and were easy targets for detector vans.
Whether the colour subcarrier either 4.43 or 8.86 mhz was ever used for detection I don't know.
I would somehow think that if detector vans were still around that todays plasma & LCD sets would be hard to pin down with all the electronic noise they produce that is not related to any received material.

Re: TV Detector Vans
 

This has been an ongoing issue. The one person who could explain the early detection [?] system would be an individual whose job it was but these seem to be rarer than the vans! Somebody must have been employed even if only to drive a dummy van around. Did it come under the Official Secrets Act I wonder? It's not really Enigma is it. Usually someone turns up here or elsewhere and says "I used to do that job". One thing is certain, the operation of the current system remains a bit of a mystery as well8-\. Those people who choose to live with out a TV [not myself] will know what I mean
Dave W

Re: TV Detector Vans
 

But why would they need detection equipment in the first place, in this day and age?
They should have a record of every address in the country, it can't be that hard to 'run down that list' with a computer.

Re: TV Detector Vans
 

There is nothing in those vans except a bench, a clipboard and a couple of blokes.

The way it worked was that a list of properties was supplied to the inspectors, who would knock on the doors and ask questions.

The handheld detectors were fake too, normally a hairdryer with LEDs.

Source: My old tutor was an inspector

Re: TV Detector Vans
 

The BBC broadcast an episode of "Punt PI" a while ago, which was pretty convincing and confirmed that there were real working TV detector vans, as well as dummy vehicles in the fleet.

My understanding is that radiated harmonics of the line timebase were detected. Changing beam current varied the loading on the timebase and gave the radiated signal a characteristic modulation, the demodulated 'sound' of which could be compared with that of the channels being broadcast at the time and hence enable the operator to deduce the channel being watched. I remember the TV ads where the white-coated boffin in the van announced in a sinister voice "... and they're watching Columbo..."

Re: TV Detector Vans
 

It's way off topic David and has probably been mentioned elsewhere on the forum but Sony got around the PAL patents by running two crystals instead of one in an obscure way to decode the PAL in a non-PAL manner (if that makes sense?) I avoided them like the plague. Far too complicated for me.

Re: TV Detector Vans
 

See here:-

http://www.tvlicensing.biz/wpblog/bl...ns_article.gif

Re: TV Detector Vans
 

Interesting Graham.
That puts some myths to bed and even the one I was told about in post 26 :dunce:

Re: TV Detector Vans
 

Interesting pic. of the antenna Graham, totaly different to pics. I have seen on the commer vans. Would that indicate a switch from line timebase detection to local osc. detection or would you say that they are one of the same, the elephants trunks on the commer look like they might contain a lot of wire. I remember seeing the commer vans but not the later ones.
?

Cheers.

Re: TV Detector Vans
 

Shows how up to date I am, I didn't know that they were not still using them. I remember them in the early days though, you would occaisionally see them in use on the TV, in fact I seem to remember them showing a scope trace purportedly from the TV in the house they were parked outside and they did say that they could tell which channel it was on. There was only a choice of two then anyway.

Slightly off topic. I had one of those Commer vans in about 1996 only a couple of years old, one of the first diesels, nearly deafened you but you couldn't half get a lot of tellies in it.

Peter

Re: TV Detector Vans
 

OK, do you not think that with the combined skill of people on this forum alone, one of us would have heard about or found the bit you need to take out/shield with foil to defeat the detector vans?

It always was and still is, a list of addresses without a license, there is no hi-tech kit in the van capable of working out where in the property the set was or what channel was being watched. We call this now a database.
Looks like the scare mongering was very effective though...

Re: TV Detector Vans
 

There are comprehensive technical articles on TV detector vans in at least two issues of the POEEJ.

1/
January 1963 (Vol 55 Part4) describes a "new" system covering bands 1, 2 and 3 (remember you needed a radio licence too in those days).
This used a rotatable elliptically polarised aerial - a tilted dipole in a large corner reflector, mounted on the roof of a Series 5 Morris Oxford Traveller estate car.
The panoramic receiver tuned 110-250 Mc/s and detected local oscillator radiation - harmonics for bands 1 & 2 and the fundamental for Band 3. The classic DF technique of taking two or more bearings was used and accuracy was claimed as 5 degrees or 3-1/2 feet laterally at 40ft range and an effective system range of 100ft.
A periscope coupled with the aerial rotation allowed the operator to view the target, and even incorporated a lamp to flash a narrow beam of light for target spotting in the dark.

This article also mentions the previous sytem, which it was replacing, as having fixed loop aerials and detecting radiation of the second harmonic of the line timebase. It had become obsolete with the introduction of ITV because signals from a mixture of sets tuned to BBC and ITV were non-synchronised and this made individual sets difficult to DF.

2/
Volume 62, pp 148 - 155 (I don't have the date to hand) describes the later system brought in when UHF sets came into use. This was the Commer 2500 van type seen in the picture referred to in post #21.
There were two aerial systems. A pair of broadband dipoles mounted either side of a common reflector was used for a preliminary scan to distinguish between direct signals and those reflected off buildings.
Much of the design effort went into devising a system that was usable in the presence of multipath reflections.
The main DF aerial was a pair of long spiral log periodics with circular polarisation, wound with copper tape on conical plastic formers. In the picture they are in the stored position - in operation they were turned to be broadside across the roof of the van. These two aerials have a spacing of 6 wavelengths, the forward one being on a track so it moves in sync with the receiver tuning.
The receiver has a panoramic display for tuning in the signal, and there is a second CRT which displays the interference pattern between the aerials as the vehicle moves past the target houses. The operator adds a mark as the van passes the suspected target. The trace from this tube is photographed with an instant (Polaroid type) camera and by studying the pattern of 7 lobes with an adjustable graticule the direction and range of the signal can be determined.
The receiver covered 470-860 MHz, picking up local oscillator radiation including harmonics of VHF sets.


The article linked to in Post #32 describes the third incarnation of the detector van which replaced the Commer Van type. It uses the same principle of displaying interference patterns, but with generally updated technology and a much more visible aerial system.

It is clear that all these systems actually worked, but with only two per PO Region there is no doubt that the deterrent effect of their high visibility produced far greater results than the actual detections.

My copies of the two earlier articles were made many years ago on chalky-surface photocopier paper - I can try scanning them but don't hold out much hope for the results.

Re: TV Detector Vans
 

Yes, just disconnect the aerial so the various radio frequency oscillations don't get radiated outside the TV's chassis. Unfortunately that kind of renders the TV a bit useless.

Re: TV Detector Vans
 

Sure fire way to defeat the detector vans is of course, to buy the license, they won't come knocking if you do!

Sorry guys, you won't convince me. It's far easier and cheaper to have a list of addresses.

Re: TV Detector Vans
 

The info given in post 37 seems to explain everything, I often wondered what the coils on the Commer van were, ie: L/F or VHF/UHF. It is now clear from reading the article as to what did what.
As has been mentioned most of the tactics carried out by the authorities seem to be based on scare mongering, this method was used on our family quite recently, the letters I received seemed to run in the vein of big brother. Being one that believes in innocent until proven guilty I just put the correspondence in the tear up and laugh dept. as we had a current license..two infact.

Lawrence.

Re: TV Detector Vans
 

Thank you! :thumbsup: It's comforting to have one's knowledge reliably confirmed, re: Post #8.

Al.

Re: TV Detector Vans
 

A list of addresses where TV sets are installed: it may well be easier and cheaper now - but for the period in question, I don't ever recall the existence of a system that required TV dealers nor aerial installers to provide installation addresses to the licensing authorities. Hence, some form of 'electronic detection' seems the only remaining possibility for combating licence fee evasion - again, for the period in question.

Al.

Re: TV Detector Vans
 

I think it worked in two ways, mainly paperwork, door knocking and assuming people would fess up.

The vans did work but they couldn't exactly cruise down the street and note all the license dodgers. They were much more difficult to get results with. However, the idea that defaulters could be detected from outside their premises was a a powerful one, hence the dummy vans and TV ads.

If you really want to play up over this, a starting point is that if an inspector turns up, you are not obliged to let them in without a search warrant and you don't confess to using a TV illegally.

Pete.

Re: TV Detector Vans
 

Coo its almost worth renting a flat and installing a few 15kHz, 4.43Mhz etc oscillators and seeing what they do!

D

Re: TV Detector Vans
 

I like your style dom!

The house I grew up in as a kid wasn't TV licensed for years, nor did the owner ever pay any parking tickets, working on the theory that as computer storage was expensive, there was only a limited space on the computer for them....Not only is the person an ex BBC employee, they also describe themselves as a Pillar of the Community! The did get prosecuted around 1986and now have ditched the car but purchased a TV license!

I also know someone who always told the inspector to "go away".
Personally speaking, its a legal requirement, regardless of the rights and wrongs, so best to get a license.

Anyway, back on topic and maybe this is the way to determine one way or the other, can anyone here demonstrate a working electronic detection system in a a real life situation?
That means kit installed in the back of a van, in the road outside a house to discover where the set is located, if it is on or off and what channel is being viewed?

Very interesting discussion chaps and I bow to your knowledge.

Re: TV Detector Vans
 

I suspect that TV detection (for license evasion) uses a multi pronged approach. Many many years ago I was arranging a talk on radio interference detection, from the GPO. I was very surprised when their contact man tuned up at my house in a detector van. He said it might be a bit over the top for an informal visit but they took any opportunity to drive around in the van. It usually produced some results.

I can imagine it is certainly possible to detect TV sets in use and may not be very difficult, though getting the precise location may be tricky. I remember a situation when I was testing a portable TV. My wife was using a dedicated word processor at the same time and I was amazed to see the text she was writing on my TV screen. It was confined to one particular channel so did not interfere with normal operation. I suspect that the signals were mains borne but never bothered to check.

My main conclusion was that to prevent any indication of use to outsiders, needs great care in the design of the TV set. The amount of garbage radiated from electronic equipment these days makes me doubt whether this happens. If someone tells me that detector vans exist and work, I am prepared to believe them. Whether they are needed is another matter. It is so easy to check whether a house that has had a license in the past still has a valid one. A computer generated letter to defaulters is no problem except to new owners who don't have a TV, it can take quite some effort to stop these letters.

Re: TV Detector Vans
 

In my experience phoning them and calmly explaining why you don't need a license works. They say on the phone and in the confirmation letter than an inspector will visit to check, but nobody did in the period of 4 years or so when we legitimately did not need a license.

You could of course do nothing, throw away all the letters and eventually an inspector will turn up, but I'd rather make one phone call and avoid all the hassle.

It depends whether you prefer a quiet life or the brief satisfaction of beating the system.

Re: TV Detector Vans
 

Oh, visits from the inspectors aren't bad if my experience is anything to go by. One turned up on the doorstep two or three months into my last spell of being unlicensed.

Inspector (after briefly explaining why she was there): "Do you have a television set at all?"
Me (smiling broadly): "Oh, lots of them......"

Cue a raised eyebrow, steadily appeased as I explained the situation, but distinctly jerking upwards again when the sitting-room set, then as now a 1984ish Bang and Olufsen, was manifestly on standby :D

I used the remote control to bring it to life, demonstrating that it was tuned to the signal output of the nearby PS2 and Xbox and that all other buttons on the remote were similarly set, and that the aerial downlead was connected to the Dynatron Berkeley radiogram. All done and dusted in five minutes or so with my giving an assurance that I didn't watch any live TV via the computer and would obtain a licence if circumstances were to change, as, two or three years later, they did...

Paul

Re: TV Detector Vans
 

Yes indeed. If you look on the web there are anti-licence sites and a lot of people see baiting the TV licensing crowd as a political cause or a sport.

I don't believe that detection evidence has ever been used in a prosecution, it's used as grounds for a search warrant and the prosecution uses evidence gathered then. Prosecutions usually rely on people incriminating themselves by confessing or not acting within their rights to prevent the gathering of evidence against them.

Re: TV Detector Vans
 

The BBC are pretty unique among broadcasters in that they sell programmes to audiences, as opposed to selling audiences to advertisers. The TV licence is what makes all this possible.

If you object to paying 40 pence a day, I respectfully suggest you get rid of your own TV and stick to watching other people's sets.

Re: TV Detector Vans
 

Only unique among UK broadcasters, there are plenty of state-funded systems out there. But my own motivation for dropping the licence fee, and all TV use, for a while came from noticing that I'd watched about six hours of programming in the previous year and reflecting that it wasn't nearly memorable enough to be worth £20 or so an hour.

Paul