User's Manual

TB9400 Installation and Operation Manual Installation 77
© Tait Limited December 2013 (Draft)
5.4.6 Tuning the Reciter
B3-Band Reciter 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 B3-band reciter covers the 148 to 174MHz frequency
band. This is split into two sub-bands: 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 reciter from the subrack and reconnect the system
control bus cable to power up the reciter.
2. Log in to the reciter and select Monitor > Interfaces > RF Interface.
For information on connecting directly to the reciter, refer to
“Connecting a Networked PC to a Base Station” on page 50.
3. Feed a signal at the currently tuned receive frequency and at a level
of –80dBm into the reciter’s RF input. Check that the RSSI reading
on the RF Interface page is –80dBm ±1dB. Note this reading.
4. Set the reciter to the new receive frequency.
Figure 5.3 Identifying the B3-band receiver front end helical filters
148 to 159MHz
159 to 174MHz