Squelch Tuning - Motorola CP150 Basic Service Manual

Receiver Tuning

4.5.2 Squelch Tuning

Note: 1. Squelch tuning can only be accomplished after reference 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 be performed so the the correct 10 dB
SINAD level can be obtained.
3. This tuning method is performed for multiple squelch tuning channels and multiple
channel spacings.
4.5.2.1 Manual Squelch Tuning
Perform the squelch tuning procedure as follows:
1. Under the Rx Align menu, select Squelch Attenuation. Select Squelch Attenuation 12.5 kHz
or Squelch Attenuation 25 kHz Channel Spacing variations (Figure 4-10).
2. Apply an RF signal modulated with a 1 kHz tone at 60% rated deviation listed in Table 4-5 for cur-
rent frequency point (F1 being the first) of 10 dB SINAD. That is, adjust the reference signal level
until 10 dB SINAD is obtained at the SINAD meter. Squelch tuning can either be done manually
(see Manual Squelch Tuning for procedure) or by Auto Squelch (see Manual Squelch Tuning for pro-
cedure). To obtain 10 dB, unmute the radio first by dragging the corresponding slider value to 1.
Channel Spacing
25 kHz
12.5 kHz
20 kHz
3. Set softpot to its maximum value to mute the radio.
Figure 4-10. Squelch Tuning Window
Table 4-5 Squelch Deviation Values
Rated System Deviation
5.0 kHz
2.5 kHz
4.0 kHz
Signal Generator Deviation
3.0 kHz
1.5 kHz
2.4 kHz
4-13