Motorola CDM1250, Basic Service Manual

Page: 58 / 92

4-16 Radio Programming and Tuning Procedures
4.5.3 Squelch Tuning
Perform the squelch tuning procedure as follows:
1. Under the Rx Align menu, select Squelch Atten . Select either Squelch Atten 12.5 kHz ,
Squelch Atten 20 kHz or Squelch Atten 25 kHz channel spacing variations.
2. Apply an RF signal modulated with a 1 kHz tone at 60% rated deviation listed in Table 4-16 for
current frequency point (F1 being the first) of 10dB SINAD. That is, adjust the reference signal
level until 10dB SINAD is obtained at the SINAD meter. Squelch tuning can either be done
manually (see page 17 for procedure) or by auto squelch (see page 17 for procedure). To obtain
10dB, unmute the radio first by dragging the corresponding slider value to 1.
Table 4-15: Rated Volume Deviation Values
Channel Spacing Rated System Deviation Signal Generator Deviation
12.5 kHz 2.5 kHz 1.5 kHz
20 kHz 4.0 kHz 2.4 kHz
20 kHz (LowBand 20 kHz
systems in North America)
5.0 kHz 3.0 kHz
25 kHz 5.0 kHz 3.0 kHz
30 kHz 5.0 kHz 3.0 kHz
Note: 1. Squelch tuning can only be accomplished after front end filter tuning and refer-
ence oscillator warping.
2. When using the test box RLN4460, the received audio output is taken from the
AC/DC METER OUT terminals with the METER OUT rotary switch set to RX. It is
recommended that rated volume tuning is performed so the correct 10dB SINAD
level can be obtained.
3. This tuning method is performed for multiple squelch tuning channels and multi-
ple channel spacings.
Table 4-16: Squelch Deviation Values
Channel Spacing Rated System Deviation Signal Generator Deviation
12.5 kHz 2.5 kHz 1.5 kHz
20 kHz 4.0 kHz 2.4 kHz
20 kHz (LowBand 20 kHz
systems in North America)
5.0 kHz 3.0 kHz
25 kHz 5.0 kHz 3.0 kHz
30 kHz 5.0 kHz 3.0 kHz