User's Manual

VHF Headstation & In-Line Amplifiers
User Handbook
Handbook Nō.-50-127201FCC Issue No:-A
Date:-14/06/2005
Page:-
9 of 45
1.3 RF Radiation Hazard
RF radiation, (especially at UHF frequencies) arising from transmitter outputs connected to
AFL’s equipment, must be considered a safety hazard.
This condition might only occur in the event of cable disconnection, or because a ‘spare’
output has been left unterminated. Either of these conditions would impair the system’s
efficiency. No investigation should be carried out until all RF power sources have been
removed. This would always be a wise precaution, despite the severe mismatch between the
impedance of an N type connector at 50Ω, and that of free space at 377Ω, which would
severely mitigate against the efficient radiation of RF power. Radio frequency burns could
also be a hazard, if any RF power carrying components were to be carelessly touched!
Antenna positions should be chosen to comply with requirements (both local & statutory)
regarding exposure of personnel to RF radiation. When connected to an antenna, the unit is
capable of producing RF field strengths, which may exceed guideline safe values especially if
used with antennas having appreciable gain. In this regard the use of directional antennas with
backscreens and a strict site rule that personnel must remain behind the screen while the RF
power is on, is strongly recommended.
Where the equipment is used near power lines, or in association with temporary masts not
having lightning protection, the use of a safety earth connected to the case-earthing bolt is
strongly advised.