Front End Filter Alignment; Figure 6-15.Battery Eliminator With Rf Connector And Sma - Motorola Astro XTS 4000 Service Manual

Radio Alignment Procedures: Front End Filter Alignment
8. Click the Program All button to save the tuned values in the radio.
9. Click the Close button to return to the Transmitter Alignments menu.
6.9

Front End Filter Alignment

This alignment procedure adjusts the front end receiver bandpass filters for the best receiver
sensitivity and selectivity. This procedure should be performed for all test frequencies to allow for
proper software interpolation of frequencies between the test frequencies in the band
(see Figure 6–16
NOTE: Rx Front End Filter Alignment is required after replacing (or servicing) the mainboard.
6.9.1 Procedure for VHF/ UHF
To align the VHF/ UHF receiver front end:
1. Click the desired frequency field.
2. Apply an RF signal with no modulation at -90 dBm on the current operating frequency.
3. Start with a softpot value (approximately 10 or 20), increase softpot in ascending order, and
note the RSSI values. The RSSI will reach a peak value and remain stable and then
decrease. Allow the limits of the peak range to be defined as RSSI PEAK - 3. Choose the
middle of the peak range and program the corresponding softpot value as the tuned softpot
value.
This procedure should only be attempted by qualified service technicians.
(VHF) below/ Figure
Figure 6–15. Battery Eliminator with RF Connector and SMA
6–17(UHF) on page 6-14
RF Connector
Battery Eliminator
).
To Power Supply
6-13