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Bredhurst Receiving and Transmitting Society |
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Syllabus Sections:- 9d RF 9d.1 Recall that the Health Protection Agency (HPA) has published Investigation levels for exposure to RF radiation for UK amateur radio. Recall that compliance with HPA investigation levels will ensure that exposures are below the recommended limits and that the lowest investigation level for electric field strength is 28V/m (at 10-146MHz). Understand that if the investigation level is exceeded the cause must be investigated and steps taken to reduce the exposure to below the investigation levels.
You have to be able to recall from memory that :-
The lowest investigation level Note particularly the words the lowest investigation level as it comes into the next section. The lowest investigation level means the level above which investigations must take place - or if you are reducing power then when it drops to the maximum allowable field strength of 28V/m (at 10-146MHz)a figure you must learn!! Note that the reading is frequency dependent. If you find that the investigation level is exceeded then the cause must be investigated and steps taken to reduce the exposure to below the investigation levels. What that means is that you have to be able to firstly calculate what levels of field strength you anticipate taking into account the power of the transmitter and the distance from the radiating elements or stray radiation. Having done a calculation have some way of checking what levels you are experiencing. A homebrew field strength meter is usually only a relative strength device as calibration is a little difficult if you do not want to have ground effects altering reading and few of us have suite "antenna farms" to carry out tests. It is however your requirement to understands the problems and dangers. Next Lightning protection
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