© Microhard Systems Inc.
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Direct human contact with
the antenna is potentially
unhealthy when a n920 is
generating
RF
energy.
Always ensure that the n920
equipment is powered down
(off) during installation.
7.0 Installation
In a long-range PTP network, Yagi antennas should be considered. There antennas
will provide for the most focused ‘RF connection’ between the two sites.
In a PMP network where Remotes are located in all directions from the Master, the
Master site will have an omni so that it can communicate with all Remotes; the Re-
motes, however, may all employ Yagi antennas ‘pointed at’ the Master.
Typically a Repeater site will employ an omni such that it can readily receive an RF
transmission from one direction and be able to readily transmit it in another.
If an application involves Remotes which are not stationary (e.g. mobile application),
all sites would likely use omni antennas so that wherever the units may be, there
should be antenna pattern coverage.
The path calculation (see Section 7.1) will determine the antenna gain requirements.
Refer to the beginning of this section to review the various factors which must be con-
sidering when deploying a network. Do not discount the importance of the RE-
QUIRED HEIGHT for the antennas within your network.
7.2.2 Coaxial Cable
The following types of coaxial cable are recommended and suitable for most applica-
tions (followed by loss at 900MHz, in dB, per 100 feet):
•
LMR 195 (10.7)
•
LMR 400 (3.9)
•
LMR 600 (2.5)
For a typical application, LMR 400 may be suitable. Where a long cable run is re-
quired - and in particular within networks where there is not a lot of margin available
-
a cable with lower loss should be considered.
When installing cable, care must be taken to not physically damage it (be particularly
careful with respect to not kinking it at any time) and to secure it properly. Care must
also be taken to affix the connectors properly - using the proper crimping tools -
and to weatherproof them.
7.2.3 Surge Arrestors
The most effective protection against lightning-induced damage is to install two light-
ning surge arrestors: one at the antenna, the other at the interface with the equip-
ment. 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-type female.
7.2.4 External Filter
Although the Nano Series 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 Nano’s antenna can desensitize the receiver.
Microhard Systems Inc.’s external cavity filter eliminates this problem. The filter has
two N-female connectors and should be connected inline at the interface to the RF
equipment.
To
comply
with
FCC
regulations, the maximum
EIRP must not exceed
36dBm.
All
installation,
maintenance, and removal
work must be done in
accordance with applicable
codes.
