TB9400/TN9275 Installation and Operation
Installation
71
© Tait International Limited
May 2023
4.5
Installing the Base Station on Site
4.5.1
General Installation Advice
When installing base stations, it is very important to observe good site
engineering rules. This is especially true when the channels are combined
into a single antenna.
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. 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.
4.5.2
Synchronization
For full Synchronization information, refer to the relevant Channel Group
System Manual.
All Transceivers
All base station transceivers operating above 700 MHz require an external
frequency reference for sufficient frequency accuracy.
P25 Phase 2 Non-
simulcast
P25 Phase 2 operation requires slot synchronization between transceivers
at a site.
Operating Frequency
Frequency Reference Input
VHF, UHF below 700 MHz Not required
UHF above 700 MHz
Required
