5-12 Radio Programming and Tuning: Receiver Tuning
5.6.3 Transmit MDC Signaling System 25 kHz Modulation Tuning
1. Under the Alignment menu, select Tx Signaling System, then select MDC 25 KHz
(Figure 5-8. Tx MDC Signaling System Modulation 25 kHz Window).
2. Press PTT Toggle and switch to PTT on the test box. This will key up the radio.
3. Read the Modulation from the Service Monitor.
4. Change the MDC signaling system modulation setting until the Tx deviation value (in Service
Monitor) lies in the range of the 25 kHz channel (as shown inTable 5-4.) by using either the
Left/Right arrows on the slider or Up/Down arrows on the Working Softpot box.
5. Press PTT Toggle to dekey the radio.
6. Press Program to commit the softpot values into the codeplug.
7. Exit the Transmit MDC Signaling System Modulation 25 kHz function.
5.7 Receiver Tuning
There are 4 variations of Receive Squelch Tuning: 12.5 kHz-Band Normal Squelch, 12.5 kHz-Band
Tight Squelch, 25 kHz-Band Normal Squelch and 25 kHz-Band Tight Squelch.
5.7.1 Service Monitor Setting
1. Initial setup using the 8920A RF Communications Test Set
a. Connect “RF IN/OUT” port on 8920A to RF adaptor on radio’s antenna port using a N-Type to
BNC cable. Connect “AUDIO IN” HI and LO on 8920A to “Rx Audio” on test box using two
BNC to BNC cables. Connect the rest according to Figure 5-2. Radio Tuning Setup.
b. On 8920A, press “Rx” under “SCREEN CONTROL”.
Figure 5-8. Tx MDC Signaling System Modulation 25 kHz Window
Table 5-5. Receiver Squelch Tuning
Squelch Type SINAD Reading (dB)
Normal 6 – 8
Tight 15 – 17
F1
F2
F3
F4
F5
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