User's Manual

Commissioning
177
8. Pan the antenna unit through a ± 10° azimuth and note down the bearing to which the
Current Downlink Signal Strength is a maximum. This value should be very near to
the peak value shown in the Peak Downlink Signal Strength box.
9. Using a 10mm spanner or socket torque the pivot bolts to 12Nm.
10. If the ST is located close to the CT (likely to be less than 1.5km is used as a
guideline), the receiving signal from the base station is high (likely to be greater than -
50dBm). The loud switch may be used to switch in approximately 30dB of attenuation
to simulate an increase the path loss, which will prevent the RX signal strength from
saturating the ST receiver (saturation of the ST receiver is exhibited as high errors in
the radio link).
Optimise SNR
1. To optimise SNR select the 'Radio Data' tab in STMON make a note of the current
Uplink and Downlink SNR.
2. Select the 'Radio Analysis' tab and click the 'turn loudswitch on' button to turn on the
loudswitch
3. Return to the 'Radio Data' view and observe the change in both the uplink and the
downlink SNR. If the SNR has improved then leave the loud switch turned on. If the
SNR has deteriorated then return to the 'Radio Analysis' view and turn the loudswitch
off.
4. Finally check that the SNR has returned to its previous level.
Link Quality / Modulation rate check
STMON is able to monitor the following link quality parameters:
o Current Downlink Modulation/FEC mode
o Receive SNR Margin
o Receive Fade Margin
o Current Uplink Modulation/FEC mode
o Transmitter Fade Margin
Each of these parameters are compared with the entered installation acceptance criteria and
pass/fail indicators displayed on STMON.
In order to enhance the accuracy of the fade margin measurement, the IF Cable type and
length (to the nearest metre) should be entered into STMON.
In order to further enhance the accuracy of the fade margin measurement, the Tx & Rx gain
offsets for a particular RF channel can be entered into STMON. These are supplied with the