Motorola STARLINE SERIES Installation And Operation Manual page 34

Figure 3-6
MDR-*MB/*/II board
To obtain maximum flatness:
1
Adjust C6 and R5 for the flattest response in the mid- to lower-portion of the passband.
2
Adjust C1 for the flattest response in the low- to mid-range of the passband.
3
Adjust C3 and R4 for a peak at approximately 100 MHz to 300 MHz using the following
steps:
a. Set R4 to minimum resistance to show where the peak occurs for this RC network
adjustment (R4/C3).
b. Align C3 until the peak is near the mid-frequency limit.
c. Increase R4 until the response is flat.
4
Adjust C2 and R3 for a peak at approximately the lowest forward frequency to 250 MHz
using the following steps:
a. Set R3 to minimum resistance.
b. Align C2 until the peak is near 70 MHz above the lowest forward frequency.
c. Increase R3 until the response is flat.
5
Adjust C7 and R2 for a peak at the lowest forward frequency using the following steps:
a. Set R2 to mid-range.
b. Align C7 until the peak is near the lowest forward frequency.
c. Increase/decrease R2 until the response is flat.
6
Adjust C4 (and if necessary, L5, located on the bottom of the MDR board) to provide a
bandwidth that extends past the highest forward frequency (750 MHz or 870 Mhz) by a
minimum of 10 MHz.
Fine tune all of the above components for the best response. The low-end flatness controls
compensate for the roll-off caused by the diplex filters. Air coils on the bottom of the
MDR-*MB/*/II board may slightly tune the upper portion of the response.
C3
C2
C7
R2
R3
R4
Amplifier Setup
C6
C4
C1
R5
MB*/* Installation and Operation Manual
3-9