Motorola EP450 service manual Manual Squelch Tuning

5-12 Radio Alignment Procedures: Receiver Tuning

5.5.2Squelch 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 recom- mended that Rated Volume Tuning be performed so the correct 10 dB SINAD level can be obtained.

3.This tuning method is performed for multiple squelch tuning channels and multiple channel spacings.

Figure 5-10. Squelch Tuning Window

5.5.2.1 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 5-10).

2.Apply an RF signal modulated with a 1 kHz tone at 60% rated deviation listed in Table 5-5for 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.

Table 5-5. Squelch Deviation Values

Channel Spacing	Rated System Deviation	Signal Generator Deviation
25 kHz	5.0 kHz	3.0 kHz
12.5 kHz	2.5 kHz	1.5 kHz
20 kHz	4.0 kHz	2.4 kHz

December 3, 2003 HKLN4215A