Motorola BLE100 - Manual (Page 32)

Amplifier Setup 3-11
BLE100 Installation and Operation Manual
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 monitor 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 3-4) and QADU (illustrated in Figure 3-5) maintain the most precise
output level of the three available methods.
Figure 3-4
ADU
AUTOMATIC
DRIVE UNIT
ADU/ _______________
Pilot frequency
Figure 3-5
QADU
AUTOMATIC
DRIVE UNIT
QADU/ _______________
Pilot frequency
To set-up the ADU/QADU:
1 Position the drive control select jumper temporarily to the MAN position and perform the
complete procedure described in Manual Gain Control if not already completed.
2 Verify that the frequency stamped on the ADU or QADU control unit is the same as the
system pilot frequency. For the ADU, the pilot frequency is a CW or an available NTSC
television channel not scrambled using sync suppression and not a digital channel. For the
QADU, the pilot signal is a QAM modulated digital channel.
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.