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Automatic drive unit/qam automatic drive unit – Motorola BT100 User Manual

Page 36

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Amplifier

Setup

3-11

BT100 Installation and Operation Manual

3

Position the drive control select jumper to

AUTO

.

4

Connect a signal-level meter to the

FWD OUT

test point and tune the meter to the high

band-edge carrier.

5

Turn the thermal level potentiometer on the TDU fully clockwise and then reduce to obtain

the level obtained in Step 9 under Manual Gain Control.

Automatic Drive Unit/QAM Automatic Drive Unit

The ADU and QADU operate by using surface acoustic wave (SAW) filters to select a pilot

frequency and then monitoring the amplitude of this frequency. Any change in signal level is fed
back to the Bode equalizer. It is assumed that the encountered signal level changes are due to

changes in cable attenuation and hybrid output associated with a change in temperature. The

Bode equalizer then changes its insertion loss to maintain a constant output level. The ADU
(illustrated in Figure 3-6) and QADU (Figure 3-7) maintain a more precise output level than

using the TDU or leaving the BT100 in manual control.

Figure 3-6
ADU

Figure 3-7
QADU

To set-up the ADU/QADU:

1

Position the drive control select jumper (Figure 2-13) temporarily to the

MAN

position and

perform the complete procedure described in Manual Gain Control if not already completed.