User's Manual

Maintenance Handbook
Baltimore Radio Repeater System
Handbook No. 60-166701HBKM Page 4 of 24
2. SAFETY CONSIDERATIONS
2.1 Earthing of Equipment
Equipment supplied from the mains must be connected to grounded outlets and earthed
in conformity with appropriate local, national and international electricity supply and
safety regulations.
2.2 Electric Shock Hazard
The risk of electrical shocks due to faulty mains driven power supplies whilst
potentially ever present in any electrical equipment, would be minimised by adherence
to good installation practice and thorough testing at the following stages:
a) Original assembly.
b) Commissioning.
c) Regular intervals, thereafter.
All test equipment must 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.
2.3 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.