Tetra / Airwave
Once upon a time, your friendly neighbourhood scoundrel would be able to listen to unencrypted Police communications using a handheld radio scanner.
These days most Police forces use the encrypted Airwave/Tetra radio system.
Tetra in the UK uses the 400MHz band and will typically have three antennas emitting 20W each. Defenders of the Tetra system point out that’s less energy than the light bulbs in your lounge emit, but I wonder how many Chief Constables or MPs would be happy to have a ‘Tetra Chandelier’ in their family home?
Also, a lot of information on the Internet states that Tetra ‘pulses’ at frequencies that may have biological effects on humans – who pulse @ 16 Hertz. In fact, the Stewart Report of 2000 recommended avoiding frequencies that were subsequently used.
Here are two photos of our own Optoelectronics Digital Scout detecting Tetra in my own property. The reading was taken in one of the hotter spots, before I did some shielding. A cheap £10 bug detector – which is supposed to have a range of just a few feet – even detected the Tetra signal at this spot. Remember this reading is at 500m from the mast, through several brick walls. In fact, I’ve seen it go as high as -29 dBm.
Each 3.0 dBm increment on the photo on the right equals a doubling of received power & a typical not-too-near-a-mast signal level would be -48.0 dBm.
Last summer I took the meter to the Hack Green Nuclear Bunker in Sandbach to see what reading you’d get in that kind of RF-free environment. In the basement of Hack Green, where you can get no mobile phone signal, it only drops to -51.0 dBm.
Links:
Telegraph story on Police Tetra mast from 2004
2010 Update – Lancashire police were the first force in the country to pilot Tetra back in 2001. The report below, from the Telegraph, states that the local branch of the Police Federation have logged 176 complaints about Tetra.
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The screenshot of your counter is wrong. Tetra frequencies for the police are from 380-385 MHz and 390-395 MHz
Therefore your article is a little misleading to say the least.
Also the equipment you have used for measured field strength would not give a very true reading. A receiver such an R&S EB-200 Miniport with a calibrated antenna would give you a true reading.
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LessRadiation replies: Greetings to you in Gibraltar Steve. Your points are quite valid. If i’d used the equipment you suggest I’d have recorded an even stronger signal level at exactly the right frequency! Surely you’re not suggesting I was picking up GSM… There are photos of the Tetra mast in question on this site. It’s transmitting at 4 times the power of the GSM mast & both are the same distance from my house. A crappy £10 bug detector with LEDs on it that can only detect a proper FM bug at 2 metres can detect the Tetra mast at 500 metres. I think my DigiScout was seeing the Tetra mast, don’t you? Shame you disagree – maybe you’re stupid?
PS I just looked up the EB-200 Miniport and it looks a bit out of my budget! I bet you don’t have one in your shack do you. That DigiScout cost me £500 and has been worth every penny… I’m sure you’re not stupid really, just pedantic.