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Section
8
Safety
8D1
Recall that the main health effect of exposure to electromagnetic
radiation is heating of body tissue and that the eyes are particularly
susceptible to damage. What is
electromagnetic radiation please ? asked one student the other night. So
here is the answer:-
As a Foundation Licence holder, if you have been operating your
transceiver then you have been using electromagnetic radiation. In fact
when you have been listening to the broadcast radio, watching the
television or even cooking in your microwave cooker you have been using
electromagnetic radiation one way or another. Electromagnetic wave is
just a fancy way of saying radio waves but there are also many other
wave that have names within the range of electromagnetic radiation as
shown in the diagram below. You can see now the change in frequency from say 1MHz at
the radio to many many many Mhz at the gamma ray end. Note also the
portion of the microwave just above radio and below infrared. Infrared is
heat rays and microwave cooker do just that with slightly lower
frequencies. The only difference in the waves is their wave length. So now you understand what electromagnetic radiation is the point here is
to know that the main health effect of electromagnetic radiation is
heating of body tissue just like you cook in a micro wave. Thus do not
touch an antenna when in use and also do not get too near to them. 8D2
Recall that guidance on safe levels of RF radiation is available from
government and international bodies, Health Security Agency and the
International Commission on Non-Ionising Radiation Protection
(ICNIRP). 8D3 Recall what a waveguide is and why it is unwise to look
down a microwave frequency waveguide or to stand close to or in front
of high-gain antennas as they may be in use. Booklets can be obtained that give
information as to what are considered "safe" radiation levels. Such
booklets are available from government and international bodies (HPA
and ICNIRP). 8D4
Recall that antenna elements and other conductors carrying RF should
not be touched whilst transmitting. What are antenna elements ? These are the
wires or other metal parts that make up the antenna. Recall
that antennas should be mounted where people will not come into
accidental contact with them. When you put up antennas, wires, feeders etc,
outside think of the location and how they are fixed. Is the
location suitable or could it be knocked by say a window cleaners
ladder? If it were knocked would the fixing be secure enough to keep
the antenna or / and cable in place? Note:
this does not apply to low powered devices such as hand-held
equipment. The origin of some of the text on this page is from the
RSGB with additions by the web master
The HPA Agency (Health Protection Agency) was established as a
non-departmental public body, replacing the National Radiological
Protection Board (HPA) and with radiation protection as part of
health protection incorporated in what is has to control.
So be aware that this change may not have filtered through to all
training courses.
When you are transmitting the sole aim of the antenna is to radiate
your signal efficiently. To do this the RF signal will at times be
at high voltage and other high current along the antenna. There is
thus a danger of RF burns even at relatively low levels of operating
power.
Don't touch an antenna when it is being used to transmit a signal
