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TV Detection
When people talk about TV licensing, one of the most discussed subjects online are the inner workings of TV detector Vans and TVL’s TV detection gadgets - and whether they actually exist.
Keeping up the myth of TV Detection is of such importance to the BBC that it claims it would lose out on funding if people are given an insight into the method of TV Detection (see also BBC statements).
Giving insight into the dark art of TV detection is exactly what the BBCresistance.com website entails to do. So, let’s get started.
The key question
Is it possible to detect a TV in operation?
Yes, with the help of electromagnetic waves.
Hang on! You just wrote that TV detection is a myth so the answer should be ‘no’, shouldn't it ?
Don't worry, we'll revisit this contradiction later on. We’ll have to cover a bit of ground first though so put on the kettle and get yourself a comfortable seat.
BBC statements
Here we have three interesting statements from the BBC regarding TV detection. These statements have been gathered from the Freedom of Information section of the BBC website.
Electromagnetic
waves
There is nothing mysterious about Electromagnetic waves. The following experiment (fig. 1) shows you how easy it is to create them yourself.
Take a 9-volt battery and a coin.
Find a radio, select AM and tune it to an area of the dial where you hear static.
Hold the battery near the antenna and tap the two terminals of the battery with the coin.
You will hear a crackle in the radio caused by the connection and disconnection of the coin.
Every time you connect the terminals electricity creates a brief magnetic field in the form of invisible waves, which are detected by the radio.
This is what it sounds like.
fig. 1
We are continuously exposed to Electromagnetic waves both from natural sources and from an array of man-made electronic devices.
A television set generates its share of Electromagnetic waves (we will prove that in this section). In fact each source, natural and man-made, carries its own Electromagnetic signature or fingerprint.
Frequency
Some Electromagnetic waves can been seen by the human eye others can’t; but they all have, at least, the following two measurable properties:
If you spin a wheel and make 1 full rotation per second, the wheel’s frequency is 1 cycle per second. You could also say the frequency (f) is 1 Hertz or f=1Hz.
If you make 2 full rotations per second the frequency is 2 cycles per second or f=2Hz.
If you manage to make 1000 full rotations per second f=1000 Hz; or to avoid having to write long numbers f=1kHz.
Hertz
The Hertz, shortened to Hz, is named after the German physicist Heinrich Hertz, who made important scientific contributions to electromagnetism.
fig. 2
Go on, rotate the wheel above (fig. 2) and create a wave!
Below (fig. 3) are a number of examples of sound frequencies. Please note that sound as in voice and music is transmitted through vibrating air molecules. Sound itself is not an electromagnetic wave.
fig. 3
Hearing test
In humans the audible range of frequencies is said to be 20Hz to 20,000Hz. Try the Frequency Sweep in fig 3. and test your hearing!
Spectrum
The electromagnetic spectrum has been divided up into frequency bands and given its own name (fig. 4). Note that Radio and Television broadcasts all sit within the range of 30 to 1000 Mhz.
fig. 4
Long-waves
Frequency range for radio broadcasts.
Radio, TV
Frequency range for radio and TV broadcasts.
Microwaves
Microwave ovens make use of this frequency range to cook your ready meals.
Infra-red
We sense this frequency range as heat (it makes our skin feel warm).
Visible
Your eyes have specialised cells that perceive this range of electromagnetic waves as colour ranging from red to violet.
Ultraviolet
The sun is a well known source of ultraviolet (UV) radiation. It is the frequency of the UV wave that causes our skin to burn.
X-rays
Your doctor uses this frequency range to look at your bones and your dentist to look at your teeth.
Gamma-rays
Radioactive materials emit gamma-rays. The biggest gamma-ray generator of all is the Universe. It makes gamma radiation in all kinds of ways called background radiation.
Transmitting broadcasts
At the heart of every transmitter is an electronic device called an oscillator. This oscillator produces an electromagnetic wave at a given frequency. After being amplified several thousand times, this electromagnetic wave is powerful enough to travel long distances in all directions covering a large area.
See fig. 5: The base frequency broadcasted (green) does not contain any meaningful information, however, by mixing this signal with audio and video (red) we can vary its frequency. The transformed broadcast signal (blue) now contains information; it acts as a carrier for the audio and video.
Receiving broadcasts
To recover a broadcast we need some sort of electronic device that can tune in to the carrier signal and translate the frequency variations we put into it back to audio and video; that device is called a television (you probably felt that coming).
The broadcast signal enters a television set through its aerial.
The next step is to mix, again, the transformed broadcast signal with another frequency, which is generated by an electronic circuit located inside the TV itself called local oscillator. With the help of other electronic circuits the television programme is then recovered and shown on the screen.
fig. 5
Analogy
Imagine you are handed a pot of RED paint (The broadcasted signal) and are told that it contains information represented by the colour YELLOW (a television programme.). How do you retrieve the information?
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The frequency of the local oscillator inside your television can be changed to tune into the various television broadcasts.
Fingerprint
The electromagnetic waves generated by a local oscillator have a very low power.
The actual frequency of the local oscillator is very hard to detect because it is virtually out-powered by frequencies generated by the other electronic circuits inside- and outside the TV.
The mixture of frequencies, however, can act as a fingerprint for an operating television set.
This fingerprint of electromagnetic waves can be made visible with a special measuring device called spectrum analyser.
fig. 6 - A spectrum analyser can reveal the presence of frequencies. It does that by scanning the electromagnetic spectrum.
Big brother
Returning to our key question whether we can detect a TV in operation the theory presented shows we can. At this point some people may get worried about their privacy. Please read on.
Putting things to the test
In terms of electromagnetic waves what does a room 'look' like with- and without the presence of a working TV?
We got a spectrum analyser out and put things to the test.
Fig. 7 shows the electromagnetic fingerprint of a room without TV. Fig 8. is the same room but this time a TV is present and switched on.
fig. 7 - TV Off.
fig. 8 - TV On. LO = Local Oscillator.
Frequency heat map
The colours in fig. 7 and 8 run from blue to white. The frequency runs from left to right (in this case 20 to 200Mhz). The elapsed time is displayed top down.
Notice the blue dashes in fig 8. These dashes are the result of frequency 'leakage' of the local oscillator. The signal is extremely weak and peaks through only intermittently. In fact the spectrum analyser has difficulties detecting the local oscillator eventhough the analyser's precision directional antenna is only a few centimeters away from the TV!
The heat maps shown above, called spectrograms, demonstrate that it is extremely hard to detect a working TV. Trying to detect a TV from the streets requires technology so advanced even the BBC, with its guaranteed yearly income, is not willing to invest in. More important: No one has ever been prosecuted on the basis of TV Detection evidence. You see, evidence cannot be heard in a court of law unless it is available
to both the prosecution and the defence, and since TV Licensing and the BBC refuse to disclose the technology they use, detection results cannot be admitted as evidence.
TV detection according the TVL/BBC
"We have a range of detection tools at our disposal in our vans. Some aspects of the equipment have been developed in such secrecy that engineers working on specific detection methods work in isolation - so not even they know how the other detection methods work. This gives us the best chance of catching licence evaders."
TV detection - The reality is ...
fig. 9 - It was science fiction then...
fig. 10 - and it still is
Defusing the myth
Fighting the myth of TV detection is not an easy task. The main reason this myth persists is that the BBC has helped perpetuate it for decades supporting the TV license ad campaign.
Luckily there is something we can do to render TV detection measurements unreliable and unfit for purpose; with the help of a smart little gadget called Television Cloaking Device.
fig. 11 - Television Cloaking Device
Click the image in fig. 11 to visit the Television Cloaking Device page, or read further to find out how this gadget works.
Smoke and mirrors
Have another look at fig. 8: The area in which the local oscillator operates lies around 40 Mhz. We also know that it is a very weak signal. Sensitive detection equipment can't produce reliable measuremeants if the scanned area is poluted by noise. Producing noise is excately what the Television Cloaking Device does best. The noise-polution distorts beyond recognition the fingerprint of a working TV.
In the design of the cloaking device the transmitted noise is generated with the help of the following three components:
A white noise source
A signal generator
(mix the two together to get gaussian noise)
And a low power transmitter to broadcast the noise between 37 and 42 Mhz
Fig. 12 shows a spectrogram of the Television Cloaking Device in action.
The noise level transmitted starts to build up at 36.9 Mhz, peaks at 39.4 and drops back to the starting level at 42.2 Mhz.
The onboard white noise source generates noise over a wider range of frequencies than those transmitted. These low power frequencies mask other areas of detection and help to distort the signature of a typical TV room.
fig. 12 - The Television Cloaking Device in action
fig. 13 - Authentic signal and its harmonics
Thanks to the simple, low cost, design of the transmitter we get so called harmonics, which present themselves as spurious signals containing no noise but still occupying parts of the frequency band; another bonus feature in cloaking your TV.
In fig. 13 we see the authentic signal and its four harmonics. Notice that each higher harmonic is less powerful than the preceding one.
Deception or detection - The final word
We have covered a lot of ground; what is an electromagnetic wave, what is frequency, frequency spectrum, transmitting and receiving broadcasts, the local oscillator and looked at electronic counter measurements to protect your privacy - that is the Television Cloaking Device.
To re-emphasise, it is irrelevant whether the detection technology the BBC/TVL claims to have actually works. Evidence cannot be heard in a court of law unless it is available to both the prosecution and the defense, and since TV Licensing and the BBC refuse to disclose the technology they use, gathered results cannot be admitted as evidence.
Deception is the exact word to describe the BBC’s tactics on collecting the TV license fee.