Ericsson LBI-31511B, Maintenance Manual, Page: 14 / 18

STEP
METERING POSITION
TUNING
CONTROL
METER
READING
PROCEDURE
GE TEST
SET
MULTIMETER
(- TO A-)
FIXED SQUELCH ADJUSTMENT (8 dB SINAD)
(EARLIER MODELS)
11. R666 Adjust fixed squelch control R666 fully clockwise (open squelch). Adjust
input level of RF Signal Generator to produce a SINAD sensitivity reading
of 8 dB. Turn R666 fully counterclockwise (maximum squelch position) to
close squelch. Slowly readjust R666 to the position where the squelch just
opens. Verify that squelch opens at 8
±
1 dBm.
MULTI-FREQUENCY SPREAD (Multi-Frequency Radios)
(Single Frequency Radio Proceed to Step 16.)
12. D
(IF AMP)
J602-10 C1-C3 Select a center frequency channel. Apply an on-frequency signal with 1 kHz
modulation to antenna jack J2. Set deviation to 3 kHz. Reduce signal level
to approximately 75% of saturated level shown on Test Set meter.
Detune C2 three turns clockwise or counterclockwise. Detune in direction
that will not exceed maximum or minimum tuning screw height. Tune C1
for a peak. Increase or decrease signal generator level as required to
maintain 75% of the saturated signal level. Detune C3 and then tune C2 for
a peak. Detune C4 and then tune C3 for a peak.
13. D
(IF AMP)
J602-10 C4, C5 Detune C5 clockwise to minimum tuning screw height. Tune C4 for a peak.
Then tune C5 to maximum tuning screw height. Tune C5 for a peak reading.
14. J101-3 C6 Select highest channel frequency and note meter reading. Select lowest
channel frequency and note reading. Tune C6 slightly to equalize these two
readings. If they cannot be equalized tune C6 to improve the channel with
lowest reading.
15. H
(RX MIX)
J2 C5 Adjust the frequency of the signal generator to the highest frequency
channel. Apply a modulated signal at the 0.35
µ
V level. Measure the SINAD
level in accordance with Step 2 of Receiver Test Procedures. If the SINAD
reading is 12 dB SINAD or less, tune C5 counterclockwise until the SINAD
reading is greater than 12 dB. Switch to the lowest frequency channel and
set the signal generator to the lowest frequency channel. Measure the
SINAD level on the distortion analyzer. If the SINAD reading is less than
12 dB, tune C5 clockwise until the SINAD reading is 12 dB. Recheck the
sensitivity at the high frequency channel. Readjust C5, if necessary, to keep
the sensitivity at the band edges greater than or equal to 12 dB SINAD.
16. D
(IF AMP)
C1-C5 Set signal generator for 12 dB SINAD level. Adjust C1-C5 for best
sensitivity.
ALIGNMENT PROCEDURE (Cont.)
LBI-31511 LBI-31511
13