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. Initially, with the enactment of the Wireless Telegraphy Act in 1923, a license was required for anyone receiving broadcasting before it was expanded to cover television in 1946. The funds generated by this venture were used as a primary funding for the British Broadcasting Corporation.
Of course, it’s okay to require a license, but without some way of implementing the measure there are no teeth. Among other measures, the BBC went so far as to use special vans to pursue illegally operating TVs and protect their precious incomes.
The van is coming for you
In order to provide a regular income, the BBC conducts enforcement operations under TV licensing trade name, the entity responsible for the administration of the system. Records are kept of licenses and expiration dates, and households suspected of having a TV set that have not paid the required fees are investigated. To encourage compliance, TV licensing regularly sends strictly worded letters to those who have left their license expired or have not purchased it. In case this fails, they can arrange a visit by law enforcement officers. These officers do not have the authority to forcibly enter homes, so in the event that a homeowner refuses to cooperate with an investigation, television 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 remote monitoring of 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 expired or missing TV licenses. If the van finds that the kit can operate and receive broadcast signals, the TV licensee can apply to the court for the necessary order to continue the investigation. Minibuses are used only to support order applications; evidence of the discovery of a van is rare, if ever used in court to prosecute for license evasion. With an order in hand, officers will use direct evidence, such as a TV set plugged into an antenna, to bring a fraudster to justice.
Detection of the use of television
The vans were first launched in 1952., with equipment designed to capture the magnetic field from the scanning of the horizontal deflection of the picture tube, at 10.125 KHz. Cyclic antennas were used to detect the second harmonic of this signal at 20.25 KHz, which was mixed with a local frequency oscillator at 19.25 KHz to create a 1 KHz tone to indicate to the operator when a signal was received. 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.
After ITV began broadcasting in 1963, this method of detection became impractical. The two TV stations did not synchronize their line scan signals, so neighboring houses watching different channels would create confusing interference for the detector. To get around this, instead, the vans switched to locating the local oscillator of the superheterodyne VHF receiver on the TV. As the stations broadcast in the 47 to 240 MHz band, it was impractical at the time to build a tuner and antenna to cover the entire band. Instead, the equipment is designed to operate at 110-250MHz, tuning the fundamental frequencies of the higher bands or harmonics of the low-frequency oscillators. A high-directional antenna was used to upgrade the kit, and a periscope was installed to allow the operator to see the house to which the antenna was aimed. If operating in the dark, the periscope can instead be used to emit 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 expired or missing licenses to help pursue the fugitives.
The introduction of UHF transmissions led to further redesign. Engineers again rely on harmonics to allow a system to cover the entire range from low VHF to higher UHF frequencies. A pair of 6 ′ long log-period spiral antennas mounted on the top of the van were used, which could be changed in distance to effectively tune different frequencies. In practice, the antennas will be aimed at a number of houses as the van moves slowly down the street. The beam model of the pair of antennas will show seven different CRT shovels in the van when a TV is detected. An operator would press a button to mark the boundaries of the CRT house when the van is moving and when the shovel model is centered on a particular house, the location of the TVs is clear. The hardware has been further refined over the years, with various antenna platforms and detection equipment used as technology.
I’m looking for TV in modern times
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 detected such signals are not as 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 both cases are uses that do not require the owner to pay a license fee. Based on an alleged submission by 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 signal. The BBC declined to respond to the request for freedom of information with any details about their methods, except to say that they used vehicles and portable devices in their enforcement efforts. However, given the many available broadcasting, cable and satellite channels, comparison efforts will certainly be much more difficult, which leads some to suspect that the days of the detector van are largely over.
While the TV license may have its days with the growing dominance of streaming content, it remains a strange piece of legislation that has sparked the development of technical curiosity. If you feel like you’re making TV noise, comment on the approach you’ve chosen to look for TVs that watch illegal content in this modern age. And don’t forget to look over your shoulder – you never know when TV licensing may knock on your door!