Service manual

8000 SERIES RECEIVER DECODER MODULE (RDM)
2-3
March 2000
Part No. 001-3139-502
2.6.2 SECOND OSCILLATOR FREQUENCY AD-
JUSTMENT
1. Set the frequency monitor to 55.7000 MHz. Monitor
the signal by inserting the pickup loop through the
opening in the shield over the second oscillator
stage.
2. Adjust L16 for the correct frequency ± 100 Hz.
2.6.3 MULTIPLIER TUNE UP
1. Connect a DC voltmeter to TP4 and adjust L20 and
L21 for a maximum meter reading (typically 0.6 V).
2. Connect a DC voltmeter to TP5 and adjust L22 and
L23 for a maximum meter reading (typically 0.7 V).
3. Connect a DC voltmeter to TP6 and adjust L24,
L25, and L26 for a maximum meter reading. Adjust
L27 for a minimum meter reading
(typically 0.8-1.0 V).
2.6.4 FRONT END AND IF ALIGNMENT
1. Preset L6, L7, L8, L9, and L10 so that the adjusting
screws are approximately 1/4 inch above the cast-
ing. Preset L11 3/4 inch above casting.
2. Set the signal generator to the receive channel fre-
quency and set the modulation for 1 kHz at ± 3 kHz
deviation. Connect the generator to Antenna 1 (J2)
and set S1 on the receiver board to "ANT 1" if
required. Adjust R87 fully clockwise.
NOTE: S1 may need to be switched again when adjust-
ing audio deviation in Logic alignment.
3. Connect an AC voltmeter and SINAD meter to the
AUDIO TEST jack on the front panel. The audio
level at this jack is not adjustable. Connect a DC
voltmeter to TP1. Increase the generator output
level until SINAD can be measured.
4. Adjust L12, L13, L14, T1, T2, T3, and T4 for max-
imum DC voltage at TP1 (reduce the generator out-
put as required to keep TP1 voltage below 1.7 volts).
5. Tune L6, L7, L8, L9, L10, and L11 for maximum
DC voltage at TP1 (reduce the generator output as in
the preceding step).
6. Repeat the adjustments in step d, tuning for maxi-
mum DC voltage. Also repeat step e, tuning for best
SINAD. Continue until no further improvement is
achieved.
7. Connect the positive lead of a DC voltmeter to TP2
and the negative lead to TP3 (both voltmeter inputs
must be floating). Set the generator output for 100
microvolts and adjust T5 for 0.0 volts DC. (T5 is
readjusted in Logic drawer adjustments.)
8. Check 12 dB SINAD sensitivity with 1 kHz modu-
lation at ± 3 kHz deviation. It should be 0.35 micro-
volt or better. If not, repeat the preceding
adjustments.
2.6.5 DIVERSITY AND SQUELCH ADJUST-
MENT
1. Preset R87 fully clockwise and set S1 to the antenna
jack being used (ANT 1 or ANT 2). Connect an AC
voltmeter to the front panel AUDIO TEST jack.
2. With no signal input, note the meter reading to
establish a 0 dB reference.
3. Move S1 to the center "DIV" position and increase
the unmodulated signal generator output to obtain 6-
7 dB quieting.
4. While listening to the audio from the speaker,
(adjust the LOCAL VOL control as required), turn
R87 counterclockwise until the audio just
squelches.
2.7 800 MHz RECEIVER PERFORMANCE
TESTS
2.7.1 SINAD SENSITIVITY
1. Set the RF signal generator to the channel frequency
with an output modulated with 1 kHz at ± 3 kHz
deviation. Connect the generator to the appropriate
antenna jack on the back panel of the receiver
drawer.