6
n920 Operating Manual
WARNING
:
To satisfy FCC RF exposure
requirements for mobile
transmitting devices, a separation
distance of 23 cm or more should
be maintained between the
antenna of this device and
persons during device operation.
To ensure compliance, operations
at closer than this distance is not
recommended. The antenna used
for this transmitter must not be
co-located in conjunction with
any other antenna or transmitter.
WARNING
:
Direct human contact with the
antenna is potentially unhealthy
when the N920 is generating RF
energy. Always ensure that the
N920 equipment is powered
down during installation.
WARNING
:
Never work on an antenna
system when there is lightning in
the area.
3.2.2 Installing External Cables, Antennas and Lightning
Arrestors
Never work on an antenna system when there is lightning in the area.
Direct human contact with the antenna is potentially unhealthy when the
N920 is generating RF energy. Always ensure that the N920 equipment is
powered down during installation. At all times a distance of 23 cm must be
maintained between the antenna and any person when the device is in
operation.
Surge Arrestors
The most effective protection against lightning is to install two lightning
(surge) arrestors, one at the antenna, the other one at the interface with the
equipment. The surge arrestor grounding system should be fully
interconnected with the transmission tower and power grounding systems to
form a single, fully integrated ground circuit. Typically, both ports on surge
arrestors are N-female.
External Filter
Although the N920 is capable of filtering out RF noise in most
environments, there are circumstances that require external filtering.
Paging towers and cellular base stations in close proximity to the N920
antenna can desensitize the receiver. Microhard Systems’ external cavity
filter eliminates this problem. The filter has two N-female ports and should
be connected in line at the interface to the RF equipment.
Weatherproofing
Type N and RTNC connectors are not weatherproof. All connectors should
be taped with rubber splicing tape (weatherproofing tape), and then coated
with a sealant.
Cabling
The following coax cables are recommended:
Table 3 Cable Loss
Cable Loss
(dB/100ft)
LMR 195
10.7
LMR 400
3.9
LMR 600
2.5
Factors to take into consideration when choosing a cable are:
•
price;
•
bend radius limitations (the lower performance cables generally can
bend more sharply)
•
performance requirements; and,
•
distance between the equipment and the antenna.
