Tait TB9300, Инструкция по установке и эксплуатации, Страница: 82 / 138

82 Installation
TB9300 Installation and Operation Manual
© Tait Limited March 2016
5.4.6 Tuning the Reciter
B-Band
Before the base station is installed on site, you may need to tune the
receiver front end. The receiver front end requires tuning if the receive
frequency is shifted more than 2MHz away from the previously set
frequency, or the RSSI level of the new frequency is more than 1dB lower
than the RSSI level of the previously set frequency.
The receiver in the B-band reciter covers one of the following frequency
bands, depending on the model:
■
B2 - 136 to 156MHz
■
B3 - 148 to 174MHz
Each of these bands is split into 2 sub-bands:
■
B2 - 136 to 146MHz and 146 to 156MHz
■
B3 - 148 to 159MHz and 159 to 174MHz
Each sub-band has its own helical filter (shown in Figure 5.3 below) which
is electronically switched in or out of circuit depending on the frequency
programmed into the reciter. The bandwidth of these helical filters is
approximately ±1.5MHz.
To check the RSSI level and tune the receiver front end (if required), follow
these steps.
1. Remove the reciterfrom the subrack and reconnect the system
control bus cable to power up the module.
Figure 5.3 Identifying the B-band receiver front end helical filters
B2: 136 to 146MHz
B3: 148 to 159MHz
B2: 146 to 156MHz
B3: 159 to 174MHz