Service manual

99R85452E01-O August 30, 2002
Radio Tuning
: Hardware Tuning Setup and Procedure 3-3
3.4 Hardware Tuning Setup and Procedure
There is a silver seal on the bottom left of the radio chassis. Remove the seal to expose the two
potentiometers for audio and sub-audio (CTCSS) modulation adjustment. RV601, which is slightly
higher, is the trimmer potentiometer for audio modulation tuning. The lower trimmer potentiometer
(RV602) is meant for sub-audio modulation tuning.
3.4.1 Audio Modulation Tuning
1. Set the radio to transmit at the appropriate tuning frequency (
See “Tuning Frequency” in Ta bl e
3-1
) with low power. Set Channel Spacing to "CS-25.0" for 25kHz (see “Radio Programming”
section).
2. On the test equipment, set it to receive at the appropriate tuning frequency (
See “Tuning
Frequency” on page 3-4
) and with the following configurations:
Audio bandwidth: 0.25Hz to 15,000Hz.
De-emphasis: OFF
3. Inject a 60mV 1kHz tone to the radio through the external mic connector.
4. Key up the radio.
5. Using a ceramic tuning tool, adjust RV601 to tune the audio modulation deviation to settle
between 4.3kHz to 4.5kHz.
Figure 3-4.
RV601
RV602