TB9100/P25 CG/P25 TAG Installation and Operation Manual Installation 59
© Tait Limited March 2014
3.5 Installing the Base Station on Site
Base Stations for Trunked Systems
When installing base stations that are part of a trunked system, it is very
important to observe good site engineering rules. This is especially true
when the channels are combined into a single antenna, particularly if the
receivers and transmitters also share the antenna, as in a duplexed system.
If at all possible, the RF planner should avoid frequency plans in which the
Rx to Tx spacing is an exact multiple of the trunked channel spacing, thus
forcing Tx intermodulation products to fall outside the Rx channels.
Cables and antennas should be of high quality construction. Solid shield
heliax type cables are best, but if braided shield cables must be used for short
distances, their braids must be silver-plated. Isolators should be used at all
transmitter outputs.
When the outputs of more than one transmitter are combined, their voltages
add, and the resulting peak envelope power is not simply the sum of their
powers, but is equal to the power of one of them multiplied by the square
of the number of sources. Cables, components, and hardware must be rated
to withstand the peak envelope power.
During the commissioning process, all transmitters should be activated together
using a diagnostic test tone, while the receiver RSSI is monitored. There
should be no perceptible increase in RSSI while the transmitters are active.
Equipment Required
It is beyond the scope of this manual to list every piece of equipment that
an installation technician should carry. However, the following tools are
specifically required for installing the base station:
■ Pozidriv PZ3 screwdriver for the M6 screws used in the DC input
terminals on the PMU; M6 (0.25in) screws are also used to secure the
subrack to the cabinet in factory-assembled systems
■ Pozidriv PZ2 screwdriver for the M4 screws used to secure the module
retaining clamps
■ 0.25in or 6mm flat blade screwdriver for the fasteners used to secure the
front panel to the subrack
■ 8mm AF spanner for the SMA connectors, and the subrack ground
connector.
You can also obtain the TBA0ST2 tool kit from your nearest regional Tait
office. It contains the basic tools needed to install, tune, and service the base
station.
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