RL-903 Receiver
Glenayre Document Number: 9110.00148
MAINTENANCE
Issue 1, Rev. C: 12/10/96
3.
Install and remove JR4 to reset synthesizer. Once synthesizer frequency is pro-
grammed, front-panel red FAULT LED should be off. If it is on, coarse tuning of
VCO may be necessary. Refer to VCO tuning procedure. If FAULT LED is off, pro-
ceed to next step.
4.
Apply standard test signal at newly programmed frequency. If test signal is heard,
programming new frequency was successful.
5.
Connect frequency counter to VCO output SMA connector that goes to RF board J2.
Frequency should be receive frequency minus 45 MHz. If 1.o. frequency is off by
more than 10 kHz, check programming steps.
6.
To precisely set reference frequency, slowly adjust U6 trim cap (if using internal ref-
erence oscillator) while checking detected audio for minimum distortion (done as part
of RF and IF Tuning Procedure).
7.
Once l.o. frequency is changed and verified, check VCO voltage using VCO Adjust-
ment Procedure.
8.
(optional) Measure l.o. injection level with spectrum analyzer or RF millivoltmeter;
level should be 15 to 17 dBm.
7.4
VCO Tuning (synthesizer board unless noted)
Perform the following procedure whenever a major change in receive frequency has been
effected or when it is necessary to check performance, especially if the FAULT LED is lit.
Even if the FAULT LED is off, a centered voltage results in improved performance over
temperature extremes and yields improved phase-noise performance.
VCO Adjustment Procedure
1.
Refer to Figure Figure 7-1.
2.
Check control voltage at TP1 (near S1). Voltage should be 5-7 Vdc.
3.
If necessary, adjust C46 to bring control voltage into range.
7.5
RF and IF Tuning (IF board unless noted)
Apply standard test signal and reduce generator level to check that receiver meets minimum
sensitivity listed in Table 2-1, Specifications. If specifications are met, tuning is not recom-
mended. Refer to Figure 7-4, RF Assembly - Adjustments, and Figure 7-5, IF Board
Controls and Indicators. Unless noted, references are to the IF board. Attach test equipment
as shown in Figure 7-2.
Second-Local-Oscillator Adjustment Procedure
Note
Hint: If sensitivity is low, and there is question whether the trouble lies
in the RF section or the IF section, inject a 45-MHz signal into IF board
P5 and adjust the 45-MHz and 455-kHz circuits. The 12-dB SINAD at
P5 should be -116 dBm or better.
Once proper operation of the IF section is validated, concentrate on the RF section and local
oscillator.
Page: 7-2
Copyright © 1996 Glenayre
Print Date: 12/05/96