A great deal of research has been done on the effects of exposure to radio
frequencies. It is generally agreed by Western scientists that the only
biologically significant property of RF energy is heating; and that this is only
a hazard if the heat is not removed quickly by the body's temperature regulating
mechanisms. This is the principle of the microwave oven and medical diathermy.
RF radiation is therefore totally different in its properties to ionising
radiations such as gamma rays and X-rays. The maximum continuous exposure to RF
was set at a power density of 10mW/cm2 over 30 years ago. This level is still accepted in
the UK and the Western
world. It has been suggested in Russia and some Eastern countries that there are
effects other than thermal ones and that the maximum power density should be 10W/cm2.
Evidence of this is regarded with suspicion in the West.
Close
proximity to a source of RF energy must therefore be avoided. Measurements of
power density made in the vicinity of various 300-400W output amateur stations
operating on 28MHz and 144MHz and their antennas have given values of less than
1mW/cm2. Calculation shows that standing 20cm from a vertical /4
antenna fed with 140W at 28MHz is equivalent to being in a 10mW/cm2
field. This is not, however, a normal situation to be in!
Microwave radiation is not itself more hazardous, but the smaller area over which microwaves are likely to radiate results in a greater power density. Any exposure to RF which results in a sensation of heat is far in excess of 10mW/cm2 and is therefore very dangerous. The eyes are particularly susceptible to damage in this way.
Situations to be avoided
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