User Manual

SECTION 2: FACTORY TEST PROCEDURE
~\Technical Documentation\System Manuals\FCC-Reports\DR4B-FCCRpt.doc Page 14
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Adjustment / Alignment Procedures
Receiver Injection
Perform the following steps to adjust the receiver injection and injection frequency:
Step 1 Using the HP high frequency probe, verify that the receiver injection frequency is
present at each of the three (3) receivers by monitoring the receivers’ R12 surface mount
pad which lies on the 50 ohm track between L3 and U3.6.
Step 2 Adjust R7 on the receiver injection circuit board to set the injection frequency within 10
Hz of the exact injection frequency. The amplitude of the injection frequency should read
approximately +5 dBm ±1 dBm.
Receiver 1
Step 1 Using the high frequency probe, monitor the 44.545 MHz second injection frequency
at U2 pin 3, adjust trimmer capacitor (C5) to the center of the oscillator’s oscillation
range. The amplitude level of pin 3 of U2 should read between +5 and +10 dBm.
Step 2 Inject an on-frequency signal at a level of –80 dBm, modulated with a 1 KHz test tone at
±5.0 KHz deviation into the receiver under test.
Step 4 While monitoring RSSI at TB1-4 with the digital multi-meter, adjust the trimmer capacitor
(C1) for maximum RSSI. The RSSI properly tuned receiver should be approximately 2.8
to 3.4 VDC.
Step 5 Check the receiver’s distortion and verify that it is less than 3%.
Step 6 Adjust C1 slightly if necessary for minimum distortion.
Step 7 Check the receiver’s sensitivity, verifying that the SINAD is 12 dB or better at a maximum
level of –119 dBm (-120 is typical).
Step 8 Repeat procedure for Receivers 2 and 3.
Diversity Reception Controller
Step 1 Inject an on-frequency signal at a level equal to Receiver 1 12dB SINAD level, modulated
with a 1 KHz test tone at ±5.0 KHz deviation into Receiver 1.
Step 2 While monitoring TP1 with the digital multi-meter, adjust RSSI1 low adjust potentiometer
(R12) for a reading of 0.750 VDC ±10 mV.
Step 3 Increase the amplitude of the signal by 50 dBm.
Step 4 While monitoring TP1 with the digital multi-meter, adjust RSSI1 high adjust potentiometer
(R11) for a reading of 2.75 VDC ±10 mV.
Adjustments R11 and R12 are interactive adjustments, therefore continue adjustments until the DC voltage
at TP1 is 0.750 VDC for the receiver’s 12 dB SINAD level and 2.75 VDC for a 50 dBm increase from the
receiver’s 12 dB SINAD level.