Handbook

PBL UHF1/1A 1 & 2 Air Interface
Maintenance Handbook
H/book Number:-60-055900HBKM
Issue No:-2
Date:-20/10/2003
Page:-
9 of 85
1. SAFETY CONSIDERATIONS
1.1 Electric Shock Hazard
Electrical shocks due to faulty mains driven power supplies.
Whilst ever potentially present in any electrical equipment, such a condition would be
minimised by quality installation practice and thorough testing at:
a) Original assembly.
b) Commissioning.
c) Regular intervals, thereafter.
All test equipment to be in good working order prior to its use. High current power supplies
can be dangerous because of the possibility of substantial arcing. Always switch off during
disconnection and reconnection.
1.2 RF Radiation Hazard
“CAUTION: This equipment is approved for antennas mounted on fixed outdoor
permanent structures. A minimum separation distance of 2 metres must be maintained
between the radiating elements and any nearby persons. A maximum antenna gain of 21
dBi may be used. Operating this equipment without regard to these restrictions will result in
RF exposure levels above the limits allowed by FCC rules.”
This equipment complies with part 90 of the FCC rules. Any changes or modifications not
expressly approved by the manufacturer could void the user’s authority to operate the
equipment.
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.
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!
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.