User's Manual

Model 1150A DVOR
9-20 Rev. - November, 2008
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e. Select Transmitters>>Configuration>>Offsets and Scale Factors. For the Tx #2 Ident Modulation Scale for
Ident Modulation, enter a value from 0 to 200% to adjust the value entered into the Nominal setting to the
correct value as determined by the viewing Monitors>>Data screen.
NOTE
Typical setting for ident modulation is 8.0% but may be adjusted according to local requirements.
9.7.13.4
Setting Transmitter Reference Modulation
a. Place Transmitter 1 on the antenna by pressing the Main #1 button on the LCU or PMDT.
b. Select Transmitters>>Configuration>>Nominal. Enter the Reference modulation to 30%, then press [F7].
The new Reference modulation will be entered into the station’s temporary memory.
c. Select Transmitters>>Configuration>>Offsets and Scale Factors. For the Tx #1 Reference Modulation
Scale for Reference Modulation, enter a value from 0 to 200% to adjust the value entered into the Nominal
setting to the correct value as determined by the viewing Monitors>>Data screen.
d. Place Transmitter 2 on the antenna by pressing the Main #2 button on the LCU or PMDT.
e. Select Transmitters>>Configuration>>Offsets and Scale Factors. For the Tx #2 Reference Modulation
Scale for Reference Modulation, enter a value from 0 to 200% to adjust the value entered into the Nominal
setting to the correct value as determined by the viewing Monitors>>Data screen.
NOTE
This value may be changed during the flight calibration. Use the
Transmitters>>Configuration>>Offsets and Scale Factors to make the required correction
9.7.13.5
Reference to Sideband Phasing
a. Set TX1 and TX2 circuit breakers to the ON position.
b. Place Transmitter 1 on the antenna by pressing the Main #1 button on the LCU or PMDT.
c. Place the monitors in bypass.
d. Connect oscilloscope to 1A4A3 J2. Note composite signal waveform. Connect the scope sync input to
1A4A3 J3 Sync output and trigger on the falling edge.
e. Adjust oscilloscope so that the composite signal is a full 30 Hz waveform (33 ms).
f. On the PMDT select Transmitters>>Configuration>>Offset and Scale Factors.
g. Adjust Tx #1 Carrier to Sideband Phase Offset (Coarse) in 90 degree increments until the waveform on the
scope and the Monitors>>Data 9960 AM level displayed by the Monitor reaches a maximum amplitude.
h. Add or subtract degrees for the Carrier Sideband Phase Offset (fine) until Monitors>>Data 9960 AM level
displayed by the Monitor reaches maximum amplitude.
i. Place Transmitter 2 on the antenna by pressing the Main #1 button on the LCU or PMDT.
j. On the PMDT select Transmitters>>Configuration>>Offset and Scale Factors.
k. Adjust Tx #2 Carrier to Sideband Phase Offset (Coarse) in 90 degree increments until the waveform on the
scope and the Monitors>>Data 9960 AM level displayed by the Monitor reaches maximum amplitude.
l. Add or subtract degrees for the Tx #2 Carrier Sideband Phase Offset (fine) until the Monitors>>Data 9960
AM level displayed by the Monitor reaches maximum amplitude.
m. Once the reference to sideband phasing values have been established save the operating parameters.
n. Switch transmitters so that Transmitter No. 1 is now operating normally.
NOTE
Further minor adjustments to the reference to sideband phasing may be made during
commissioning flight check. This phase adjustment may increase the 9960 AM level as
determined by the flight check panel technician. If during flight check the 9960 modulation is less
than 30 percent the Reference-Sideband Phasing Parameter should be adjusted slightly to find the
peak reading as determined by the panel technician. This will provide better sideband efficiency
than by increasing the sideband power higher.