TV Detector Vans Once Prowled The Streets Of England

The United Kingdom is somewhat unique in the world, as it requires those households that watch television to purchase a license for the privilege. Originally enacted by the Wireless Telegraphy Act in 1923, the license was required for anyone who received broadcasting before it was expanded to cover television in 1946. The funds generated by this venture were used as basic funding for The British Broadcasting Corporation.

A typical TV license invoice. There are still separate licenses for black and white and color kits, with 6,000 black and white licenses issued in 2019.

Of course, everything is fine to require a license, but without some way of implementation, the measure has no teeth. Among other measures, the BBC went so far as to use special vans to hunt down illegally operating TVs and protect its valuable income.

The van is coming for you

To provide a regular income, the BBC conducts enforcement operations on TV licensing trade name, the entity responsible for the administration of the system. Records are kept of licenses and their expiry dates, and investigations are conducted into households suspected of owning a television set that have not paid the required fees. To encourage compliance, TV Licensing regularly sends strictly worded letters to those who allow their license to expire or have not purchased it. In the event of failure, they may arrange a visit by enforcement officers. These officers are not authorized to enter homes forcibly, so in the event that a homeowner refuses to cooperate with an investigation, TV Licensing will apply for a search warrant. This can be based on evidence such as a satellite dish or antenna spotted on the roof of a home, or a remote spying on a sofa cushion through a window.

Alternatively, a search warrant may be issued based on evidence gathered from a television detector van. Equipped with equipment to detect used TVs, vans roam the streets of the UK, often sent to addresses with revoked or missing TV licenses. If the van finds that a kit can operate and receive broadcast signals, TV Licensing can apply to the court for the necessary order to continue the investigation. Vans are used almost exclusively to support order orders; evidence of the discovery of a van is rarely used, if at all, used in court to prosecute a concealer of a license. With an order in hand, officers will use direct evidence such as a TV set plugged into an air antenna to bring a fugitive to court.

Detection of the use of television

An example of the original design of the detector van, deployed in 1952. Note the three loop antennas – one front, two rear.

The vans were first deployed in 1952., with equipment designed to capture the magnetic field from the horizontal deflection scan of the picture tube, at 10.125 KHz. The loop antennas were used to detect the second harmonic of this signal at 20.25 KHz, which was mixed with a local beating frequency generator at 19.25 KHz to create a 1 KHz tone to indicate to the operator when it was received. signal. Three antennas were used, one at the front of the van and two at the rear on the left and right. When the van was next to a working TV in the house, the signal between the front and side antennas would be approximately the same. The signal from the right and left antennas can then be compared to determine which side of the street the TV is on.

The VHF era brought with it a new design of a detector van, this time built on a car, so as to avoid problems with the clearance with the high antenna.

After ITV began broadcasting in 1963, this method of detection became impractical. The two TV stations do not synchronize their line scan signals, so neighboring houses watching different channels would create confusing interference for the detector. To get around this, the vans proceeded to detect the local oscillator of the superheterodyne VHF receiver on the TV. With stations broadcasting in bands from 47 to 240 MHz, it was impractical at the time to build a tuner and antenna to cover this entire band. Instead, the equipment is designed to operate from a 110-250MHz tuning in the fundamental frequencies of the higher frequency bands or harmonics of the lower frequency oscillators. A highly directional antenna was used to refine the kit, and a periscope was installed that allowed the operator to see the house to which the antenna was pointing. If operating in the dark, the periscope can instead be used to illuminate a small point of light in the direction of the antenna to identify the target. The results were crossed with a list of houses with revoked or missing licenses to help search for fugitives.

A pair of antennas were used to search for TVs in the UHF era, with dual tuning helping to improve direction.

The introduction of UHF transmissions led to further processing. Engineers again relied on harmonics to allow a system to cover the entire range from low VHF to higher UHF frequencies. A pair of 6 ‘long daily periodic helical antennas mounted at the top of the van are used, which can be changed at a distance to effectively tune different frequencies. In fact, the antennas would be aimed at a number of houses as the van drove slowly down the street. The antenna pair beam model will show seven separate CRT blades inside the van when a TV is detected. The operator would press a button to mark the boundaries of the CRT’s house as the van moved, and when the lobe model was centered on a particular house, the location of the TVs was clear. The hardware has been further refined over the years, with various antenna platforms and detection equipment used as technology.

The demand for television in modern times

In the UHF era, fixing outdoor TV reception took a bit of finesse, with the operator having to interpret signals received on a CRT display.

Modern efforts to detect license evasion are shrouded in mystery. Modern flat screens that receive digital TV signals do not emit as much radio frequency interference as older designs, and all such open signals are more easily connected to the broadcast TV. The LCD TV in the home can just as easily display the output of a video game console or online streaming service, and in both cases there are cases where the owner does not require a license fee. Based on an alleged submission to the BBC for a search warrant in recent years, optical methods can be used in which the reflected light from a TV set in the viewer’s home is compared to a live broadcast signal. The BBC declined to respond to the request for freedom of information with any details about their methods, other than saying it had used vehicles and portable devices in its enforcement efforts. However, given the many broadcast, cable and satellite channels that are now available, comparison efforts will inevitably be much more difficult. which leads some to suspect that the days of the van-detector are largely over.

Although the days of the TV license can be numbered with the increased dominance of streaming content, it remains a strange piece of legislation that arouses the development of technical curiosity. If you like a TV movie, sound in the comments with your chosen approach to hunting down TVs that watch illegally broadcast content in this modern age. And don’t forget to look over your shoulder – you never know when a TV license may be knocking on your door!