Motorola BLE100 operation manual Automatic Drive Unit/QAM Automatic Drive Unit

Amplifier Setup 3-11

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:

1Position the drive control select jumper temporarily to the MAN position and perform the complete procedure described in Manual Gain Control if not already completed.

2Verify 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.

3Position the drive control select jumper to AUTO.

4Connect a signal-level meter to the FWD OUT test point and tune the meter to the high band-edge carrier.

BLE100 Installation and Operation Manual