Standard Communications mt930b, Руководство по обслуживанию, Страница: 65 / 155

Maintenance
MT930B
Service Manua
l Page 6-33
Figure 6-18. Delay Characteristics
2. Call up the file 27MHz_BPF, and adjust the variable attenuator so the point
of intersection within the frame and the 70 MHz point match.
3. Turn cores LF13, LF16, and LF17 (LF53, LF56, and LF57) to adjust the
pass-thru bandwidth and delay characteristics to the specified values (so
they lie within the frame). If adjustment using only the above cores, turn
cores LF11 and LF15 (LF51 and LF55) to compensate. If adjustment is still
impossible, turn LF12 (LF52) and LF14 (LF54) to compensate.
Be sure to adjust so the delay is nearly the same height as the left and right
peaks.
4. Adjust the IF BW 27 MHz Ku filter the same as in step 3. The cores to be
adjusted are those indicated inside the parentheses in step 3.
Adjustment Specifications:
−−−− Deviation Within Pass-thru Bandwidth 70 MHz ± 8.0 MHz: ± 0.3 dB
−−−− Delay deviation 70 MHz ± 5.0 MHz: 2 nsec
−−−− –3 dB bandwidth 70 MHz ± 13.5 MHz: ± 0.75 MHz
36 MHz BPF Adjustment
Adjustment Procedure:
1. See Figures 6-19 and 6-20, and select IF BW 36 MHz-C. Call up the file
NULL_36M, and adjust the input level, using variable attenuator, so the null
point is clearly visible, and adjust each null point to the position shown by
the markers (See Table 6-4).
Table 6-4. Markers and Their Adjustment Coils
Null Point
(Marker Number) Core to Adjust
1 L32 (LF72)
2 L31 (LF71)
4 L34 (LF74)
5 L35 (LF75)
2. Call up the file 36MHz_BPF, and adjust the variable attenuator so the point
of intersection within the frame and the 70 MHz point match.
Marker Number
▼ 1: 27.25 MHz
▼ 2: 38.50 MHz
▼ 3: 70.00 MHz
▼ 4: 104.50 MHz
▼ 5: 144.25 MHz
▼ 6: 52.00 MHz
▼ 7: 88.00 MHz