Pll Frequency Adjustment; Modulation Level Adjustment And Confirmation - Standard Horizon GX1250SA Service Manual

4.6 PLL Frequency Adjustment

Adjust transmission frequency and receiving local frequency.
- Adjustment -
Figure 4-5
(a) Press PTT in CH16 and adjust CP08 to set transmission
frequency to 156.800MHz.
(Frequency must be set within ± 50Hz for adjustment while
it is in ± 750Hz in the spec.)

4.7 Modulation Level Adjustment and Confirmation

This section is to adjust modulation level on transmission.
- Adjustment -
(a) Connect MIC tool (a tool for deviation measurement: de-
scribed in Appendix 1, see page 19) to JL01.
(b) Set channel to CH16. Set Audio Generator output level to
400mV(at 1kHz).
(c) Turn PTT on and transmit.
(d) Adjust RM12 to set the reading of Modulation Analyzer to
± 4.5kHz.
(e) Turn 20dB down the output level of Audio Generator (Out-
put level becomes 1/10).
(f) Adjust output level of Audio Generator to set reading of
Modulation Analyzer to ± 3.0kHz. (This level is standard
modulation input level.)
(g) Turn 20dB up (10 times) the output of Audio Generator
from the standard modulation input level.
(h) Confirm that the reading of Modulation Analyzer is in ±
4.4kHz to ± 4.6kHz.
(i) Repeat the step (d) to (g) several times.
- Confirmation -
(a) Set Audio Generator output.
Modulation frequency is 1kHz and level is 20dB up (10
times) from the standard modulation input level.
(Example: if the standard modulation input level is 38mV
then 20dB up is 380mV.)
(b) Set channel to EXP01, turn PTT on then check modula-
tion level and modulated wave form.
Check that detected modulation level is in ± 4.3kHz to ±
5.0kHz. (Check EXP02 likewise.)
(c) Set channel to EXP04, turn PTT on then check modula-
tion level.
Check that detected modulation level is in ± 4.0kHz to ±
5.5kHz. (Check EXP05 likewise.)
15
Figure 4-6