Maxon SD170EX Series - Page 20

Service Manual SD170EX Series
Page 20 of 38
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-513 or ACC-514) 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 the adjustment of the RX VCO, check the VCO Control voltage.
Set the unit to the highest receiving frequency, 480MHz (U2), 174MHz (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 440MHz (U2), 146(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
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