TESTS AND ADJUSTMENTS
3-30
Set the Ident Control to CONTINUOUS from the RMM Program or the Local Display/Key-
board.
On the Field Test Set, press IDENT.
1020 Hz modulation depth can be adjusted from the RMM Program or the Local Display/Key-
board.
Adjust modulation depth to 10.0% +/-0.3%.
If VOICE modulation is implemented, the ident modulation depth should be set to 5.5% +/-
0.3% to avoid over modulation. Before this adjustment is done, follow the instructions in the
appendix VOICE GENERATOR. Make sure VOICE is turned off from the RMM program or the
Local Keyboard/Display when adjusting the modulation depth.
3.1.8.2 Method 2
An alternative method of checking 1020 Hz modulation depth to 10% is described below:
Connect the oscilloscope to the BNC test Connector labelled CSB.
Switch off the 90 Hz modulation and the 1020 Hz modulation.
Note the peak-to-peak deflection of the remaining 150 Hz waveform.
Then switch off the 150 Hz modulation and switch the 1020 Hz modulation to CONTINUOUS.
The observed 1020 Hz peak-to-peak waveform amplitude should be 50% of the 150 Hz ampli-
tude providing the 1020 Hz modulation depth is 10% (or 1/2 of 150 Hz depth).
3.1.9
RF Frequency Adjustment
Fine-adjustment of the operating frequency can be carried out by adjusting C1 in the
OS1221A/B RF Oscillator module.
Mount the Oscillator OS1221A/B on an extension board.
In order to monitor the frequency, connect the Frequency Counter to the BNC test connector
labelled CSB. (Make sure the transmitter under test is routed to Antenna). If necessary for sta-
ble counting switch off modulation tones.
Adjust until frequency is less than 1 kHz from operating frequency. Trimmer C1 adjusts course
and clearance frequencies simultaneously.
3.2
Antenna System Adjustments
After the transmitters has been aligned correctly the antenna system must be aligned. This
includes mechanical adjustments of the Antenna System, electrical adjustments (phasing)
and adjustments of the ADU and MCU.
For details, refer to the adjustment procedure for each antenna system.
