Motorola STARLINE SERIES Instructions d'exploitation télécharger pdf (Page 30)

Amplifier Setup 3-9

BLE*/* Installation and Operation Manual

Amplifier Level Control

Signal levels vary in a cable system primarily because cable attenuation changes with

temperature. Other components such as passives and amplifier hybrids are also affected by

temperature changes. To automatically compensate for these signal level fluctuations and

control output level, you must select the optional ADU or TDU. For improved output level

stability, use of the ADU or TDU is recommended.

When necessary and appropriate, you can also use manual gain control. The BLE*/* gain is then

determined by the potentiometer marked

MAN on the electronics chassis cover.

Manual Gain Control

To use manual gain control:

1 Verify that the electronics chassis is installed correctly.

2 Ensure that there is continuity in the forward path by installing the design-value input

equalizer and design value input JXP-*B attenuator.

3 Ensure that the drive control select jumper is in the MAN position.

4 Use a signal-level meter to measure the high band-edge carrier input level at the input test

point: 750 MHz = channel 116, 870 MHz = channel 136.

This carrier should be at standard analog level, non-scrambled.

5 Verify that the input level agrees with the design specification input.

If the level is different from design, adjust accordingly. For example: the design level is

19 dBmV at the highest frequency and the design pad value is JXP-3B. If the actual

measured level is 21 dBmV, then you must change the pad to a JXP-5B.

If the actual levels are significantly different from the design levels, it is recommended that

you investigate or consult system management before proceeding.

6 Connect the signal-level meter to the output test point and tune the meter to the high-end

channel.

7 Turn the manual gain reserve (MAN) control (illustrated in Figure 2-8) to maximum (fully

clockwise) and then reduce the output as noted in Table 3-3 below:

Table 3-3

Gain reserve versus ambient temperature

Temperature Gain Reserve

Above 110°F (43°C)

3 dB

32°F (0°C) to 110°F (43°C)

4 dB

Below 32°F (0°C)

5 dB

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 48 49

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Motorola STARLINE SERIES Instructions d'exploitation Page 30