Codan Radio Communications VT-3-150-SN User Manual
Audio Processor Board Instruction Manual
4-1
4
ALIGNMENT
Verify the standard factory settings for the MT-3 FM Audio Processor as given in section 1 before
beginning the standard deviation adjustment procedure. If the transmitter's operating frequency is
changed beyond the factory recommended bandwidth or if the synthesizer is changed, the FM
Audio Processor should be realigned to optimize the transmitter's performance. The schematic
diagram for the FM Audio Processor is shown in section 7-2 of this manual.
The settings tolerance is +/- 0.1 kHz.
beginning the standard deviation adjustment procedure. If the transmitter's operating frequency is
changed beyond the factory recommended bandwidth or if the synthesizer is changed, the FM
Audio Processor should be realigned to optimize the transmitter's performance. The schematic
diagram for the FM Audio Processor is shown in section 7-2 of this manual.
The settings tolerance is +/- 0.1 kHz.
4.1
Standard Deviation Adjustment
Set up the Communications Analyzer :
-Audio filter to LOW PASS 15 or 20 kHz
-To monitor transmit frequency and audio deviation level.
-To monitor transmit frequency and audio deviation level.
4.2
Balanced Input Setup
1
Connect audio generator output to the BALANCED INPUT (Transmitter
Main Board edge connector pins B18, Z18).
Main Board edge connector pins B18, Z18).
2
Preset
R31 (BALANCED INPUT LEVEL CONTROL)
R38 (COMPRESSION CONTROL)
R29 (DEVIATION CONTROL)
all maximum clockwise
R38 (COMPRESSION CONTROL)
R29 (DEVIATION CONTROL)
all maximum clockwise
3
Set audio generator to 2.4 kHz at 0 dBm.
4
Adjust R29 for ±4.8 kHz (Wideband) or ±2.4 kHz (Narrowband).
5
Set audio generator to 1 kHz at 0dBm
6
Set R38 for ±4.2 kHz (Wideband) or ±2.1 kHz (Narrowband).
7
Repeat steps c) to f) (slight interaction)
8
Set audio generator to 1 kHz at –8 dBm
9
Adjust R31 for ±3.0 kHz (Wideband) or ±1.5 kHz (Narrowband).
10
Set audio generator to 1 kHz at –18 dBm
11
Ensure deviation is at ±1.0 kHz (Wideband) or ±0.5 kHz (Narrowband).
12
Set audio generator to 1 kHz at –8 dBm. Set Communications Analyzer Audio
Filter to BANDPASS 300-3400 Hz. Activate distortion analyzer. Confirm that
the distortion is within specification.
Filter to BANDPASS 300-3400 Hz. Activate distortion analyzer. Confirm that
the distortion is within specification.
4.3
Microphone Input Setup
1.
Set R2 fully clockwise
2.
Apply a 1 kHz tone at 0 dBm to the microphone audio input (PIN 1 on the front
panel connector. Pin 2 is ground). Set R63 (MICROPHONE
COMPRESSION for ±4.2 kHz (Wideband) or ±2.1 kHz (Narrowband).
panel connector. Pin 2 is ground). Set R63 (MICROPHONE
COMPRESSION for ±4.2 kHz (Wideband) or ±2.1 kHz (Narrowband).
3.
Reduce the audio generator level to –10 dBm. Adjust R2 (MICROPHONE
INPUT LEVEL) for ±3.0 kHz (Wideband) or ±1.5 kHz (Narrowband).
INPUT LEVEL) for ±3.0 kHz (Wideband) or ±1.5 kHz (Narrowband).