B e n c h S e t u p
3 - 9
S G 2 0 0 0 I n s t a l l a t i o n a n d O p e r a t i o n M a n u a l
9
Remeasure the output level. It should be within 1 dB of the preferred level. If necessary, adjust
the manual gain control. Check the remaining ports and add JXP pads to bring the outputs to the
correct level.
10
Set the gain reserves using one of the following gain control options. Adjust the selected gain
control option using the procedure presented in the appropriate subsection below.
S
Manual control only — there is no compensation for changes in amplifier gain due to input
level or temperature fluctuations.
T
Thermal control — the standard thermal control unit (TCU) is installed at the factory and
compensates for gain changes due to temperature fluctuations only.
T
Automatic level control — the optional ADU drive unit holds output levels constant despite
fluctuations in temperature or input level. The ADU is available as a factory-installed option.
You can also install an ADU in place of the standard TCU in the field.
Manua l Gain Control
1
Connect a signal level meter to the
FORWARD TEST POINT
and tune it to a channel near 750 MHz.
2
Position the drive selector horizontally. Figure 3-2 illustrates the location of the
AUTO
/
MAN
drive
selector.
3
Turn the gain control (
MAN ADJ
) to maximum (fully clockwise) and then turn it
counterclockwise to reduce the output by 4 dB. If the output level is greater than required,
change the pad at the receiver output location to obtain the desired level. To calculate the correct
pad value, subtract the desired level from the measured level and increase the pad by that
amount. Note: Do not install a pad larger than 15 dB at the receiver output. If more attenuation is
needed, put the remaining amount at the interstage pad location.
Thermal Control, Model TCU
1
Perform steps 1 through 3 under Manual Gain Control.
2
Position the drive unit selector vertically.
3
Turn the level control potentiometer on the TCU to the preferred output level.
Automa tic Level Control, Model ADU
The system must contain a non-scrambled analog channel at the ADU pilot frequency.
1
Perform steps 1 through 3 under Manual Gain Control.
2
Position the drive unit selector vertically.
3
Turn the
ADU ADJ
control on the main board to the preferred output level.
Содержание Starline SG 2000
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