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3-12
Amplifier Setup
Verify that the frequency stamped on the ADU/QADU control unit is the same as the system
2
pilot frequency. For the ADU, the pilot frequency is a CW pilot 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.
Position the drive control select jumper to
3
Connect a signal-level meter to the
4
band-edge carrier.
Turn the auto level (ADU) potentiometer (illustrated in Figure 2-13) fully clockwise and
5
then reduce to obtain the level obtained in Step 9 under Manual Gain Control.
ADU/QADU Pads and Levels
This subsection provides information regarding the proper ADU/QADU padding requirements
for the BT100.
A JXP-*B pad is installed in the input line to the ADU/QADU location. This pad adjusts the
ADU/QADU input level for the standard application of the BT100 but you can change this pad
depending on the operational output of the BT100.
In the BT100 analog ADU circuit, a JXP-7B pad is generally recommended. This is the standard
ADU pad value as shipped from the factory and is appropriate for an amplifier output level
range from +43 dBmV to +49 dBmV at 550 MHz. Use a JXP-1B pad for output levels below
+43 dBmV and a JXP-11B for output levels above +49 dBmV.
The standard pad for the QADU is a JXP-0B. This pad value works for a BT100 output level
from +38 dBmV to +47 dBmV at 550 MHz. Use a JXP-7B when operating above +47 dBmV at
550 MHz.
Motorola does not recommend operating the BT100 above +46 dBmV at 550 MHz.
Use of an ADU or QADU is recommended for improved output level stability although you can
operate the BT100 in the manual mode. Select manual mode by placing the drive control select
jumper, illustrated in Figure 2-13, in the
determined by the potentiometer marked
Return Path Alignment
The following subsections describe the BT100 alignment procedures required for proper
performance in the return path.
Before You Begin
Before you begin to set-up the amplifier and perform return-path alignment, please read the
following instructions and recommendations.
For proper return alignment obtain:
RF alignment levels and insertion points for all BT100s
RF reference output level of the headend optical receivers
Equipment required for return-path alignment includes:
Full complement of JXP-*B pads and STARLINE Return Equalizers (SRE-100-*)
BT100 Installation and Operation Manual
.
AUTO
test point and tune the meter to the high
FWD OUT
position. The gain of the BT100 is then
MAN
on the amplifier cover.
MAN
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