Safety levels

What is considered a safe level of exposure to this kind of radiation? It depends where in the world you live. If you live in the UK, the guidelines are set by the National Radiological Protection Board, NRPB who have recently adopted the levels set by the ICNIRP. If you live elsewhere, including China, the guidelines will be far stricter.

Alasdair Philips of Powerwatch comments that modern scientific concern has been taken on board by a number of countries when setting guidance for the maximum signals from base stations that members of the public should be subjected to. He notes the guidelines, (as volts per metre) and gives the analogy of speed limits, with the Salzburg limit set as 30mph. (The Salzburg limits refer to the 'Salzburg Resolution' of 19 international scientists and public health doctors.)

For 1800MHz, public exposure guidelines are as follows: the first column as volts per metre, the second as mph.

To pulse or not to pulse...

Critics of the TETRA system say that a worrying feature of it is that of pulsing. 02 and the NRPB admit that the handsets pulse but they insist that base stations do not pulse, because emissions do not drop to zero. (Which is rather like saying that humans do not have a pulse, because the pressure in the veins never goes to exactly zero.) Others disagree. There is a periodic signal pattern (modulation) at 17.6Hz, says Grahame Blackwell. Alasdair Philips challenges the NRPB view, insisting that the masts do pulse and that the NRPB misinterpret the readings because they average out the pulses over time. (If you average it out, of course it's continuous.) If you look at the mast signals as an electrical engineer you could interpret them as not pulsing, but if you're looking as a biophysicist with knowledge of the human brain, you will interpret the signals differently. Precisely because the modulation of TETRA occurs at a frequency which the brain normally uses, the brain will notice the modulated frequency and not the average signal level. Alan Preece, Professor of Medical Physics at Bristol University referred to TETRA masts pulsing and said that there is a modulation of the TETRA transmission from the mast. The NRPB's attempt to deny it was, he said, splitting hairs.(32)