Service manual

Service Manual SD170E Series

Page 20 of 44

Sweep the audio frequency from 300 Hz to 4 kHz and ensure that the peak deviation does

not exceed the limits shown below. If necessary adjust RV2 to vary audio deviation.

12.5 kHz channel spacing <= 2.5 kHz dev.

20 kHz channel spacing <= 4 kHz dev.

25 kHz channel spacing <= 5 kHz dev.

Note: When using one of the internal modems (ACC-513E or ACC-514E) a test signal needs to

be applied to the radio (e.g. data from the computer). The deviation levels should not exceed the

limits as shown above.

APC (output power)

When using the extender board (ACC-516) there is a voltage drop in transmission mode

and so output power drops. As a result the radio outputs higher power than assigned

after assembly. To prevent over-power output, follow below procedure

Adjust RV4 to set high power at the point of 4.6W.

Adjust RV3 to set low power at 0.6W

Assemble the radio and again check if RF transmission power is near 5.0W for high

power and 1W for low power.

RECEIVER

Refer to figure 4.5 in the Commissioning section for details on test equipment connection

RX VCO

RX VCO is pre-tuned at the factory and adjustment should not be required

To verify adjustment of the RX VCO, check the VCO Control voltage.

Set the unit to the highest receive frequency, 490 MHz (U2), 174 MHz (V2) and verify the

VCO control voltage is under 10.0 Volts. If necessary adjust C308 of RX VCO to 10.0 Volts

Set the unit to the lowest receive frequency 440 MHz (U2), 146 MHz (V2) and verify that the

VCO voltage is above 2.0 Volts. If necessary adjust C308 to 2.0 Volts.

Note: Use TP1 to measure the voltage.

AUDIO OUTPUT LEVEL Adjustment

Set the RF signal generator to the receiver frequency of the radio and set the AF modulation

signal to 1 kHz with the following deviations depending on channel spacing:

1.5 kHz deviation for 12.5 kHz channel spacing

2.4 kHz deviation for 20 kHz channel spacing

3 kHz deviation for 25 kHz channel spacing