Receiving If Adjustment; Receiving Sensitivity Confirmation - Standard Horizon GX1250SA Service Manual

Remark:
¡ Not to saturate RF Amplifier and Spectrum Analyzer ad-
just tracking output level.
¡ Figure 4-9 is just a guide. The form varies upon measure-
ment system. Critical points are: keep ratio of the stop
band around 150MHz as much as possible and rise around
156MHz of the form.
¡ Adjust each coil within about 2 rotations from the initial
position to both left and right side.
- Confirmation -
(a) Measure SINAD sensitivity of EXP01 (156.050MHz) and
EXP05 (162.025MHz).
(b) Check that 12dB SINAD sensitivity is under -2dB for both
channel.
(c) Measure SINAD sensitivity of WX10 (163.275MHz).
(d) Check that 12dB SINAD sensitivity is under +1dB.

4.10 Receiving IF Adjustment

Adjust receiving IF Coil.
Figure 4-10
- Adjustment -
(a) Setup GX1250SA as shown in Figure 4-10 and set chan-
nel to CH06 (156.300MHz).
(b) With receiving the signal from Signal Generator, adjust
LR30 and LR31 to the positions where reading value of
DC voltage meter that is connected to the test point
(marked "IF TP") becomes highest.
While doing this, adjust output of Signal Generator not to
saturate DC voltage meter.

4.11 Receiving Sensitivity Confirmation

- Confirmation -
(a) Connect devices as shown in Figure 10 -1 and check sen-
sitivity at CH06 (156.300MHz) and CH28 (162.000MHz).
12 dB SINAD ≤ 0.45uV
20 dB QS
(b) Check sensitivity at EXP06 (163.575MHz) and EXP04
(155.050MHz) likewise.
12 dB SINAD ≤ 0.70uV
If these are not in the range above, repeat adjustments form
" 4.8 Receiving Local Adjustment " to " 4.10 Receiving IF
Adjustment".
17
Figure 4-11
≤ 0.5uV