Motorola MTR2000 T5544 Instruction / Field Service Manual page 153

H4
H3
Tuning
Cavities H2
HI
Figure 9.
Varactor-Tuned Preselector Tuning Procedure
Note
68P81096E17-E
09/30/05
To Receiver
Module
To antenna
connector
Location of Tuning Screws and Cavity Probe Holes
The Receiver Module may contain a varactor-tuned preselector which
must be retuned whenever the Receiver Module CLN1211 replaced in the
field. The tuning procedure requires application of an RF signal into the
receiver and use of the RSS Service menu to set the high and low align-
ment values of the varactor-tuned preselector. Either the Received Signal
Strength Indicator (RSSI) value (if available) or SINAD is read and peaked
by changing the preselector alignment values via the RSS. The alignment
values 132.025 MHz, 146.025 MHz, 160.025 MHz, and 173.975.025 MHz
are stored in memory (within the Station Control Module).
These four alignment values are the only information required to interpo-
late the tuning voltage of the preselector to any frequency within the 132
to 174 MHz band. To retune this preselector, perform the Varactor-Tuned
Preselector alignment procedure located in the RSS Service menu Online
Help facility.
The RSSI can be monitored at pin C11 of the Systems connector (J5) on the
station backplane (refer to Figure 10 for the location).
Troubleshooting
5
4
Tuning
3
Screws
2
1
Preselector
Assembly
39