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Attenuator
Decoupling
In 681XXCs equipped with option 2 step attenua
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tors, the ALC and attenuator work in conjunction to
provide leveled output power down to –140 dBm. In
the normal (coupled) leveling mode, when the de
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sired power level is set, the correct combination of
ALC level and attenuator setting is determined by
the instrument firmware. In some applications, such
as receiver sensitivity testing, it is desireable to con
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trol the ALC level and attenuator setting separately
by decoupling the step attenuator from the ALC.
The ALC mode menu lets you select attenuator
decoupling.
At the ALC Mode menu, press Atten Menu . The
Attenuator Menu (below) is displayed.
This menu lets you decouple the step attenuator
from the ALC, set the power level, and set the at-
tenuation in 10 dB steps.
Press Decouple to decouple the step attenuator
from the ALC.
Press Edit L1 to open the power level parameter for
editing. Edit the current level using the cursor con
-
trol key or rotary data knob or enter a new value us
-
ing the key pad and appropriate termination key.
When you have finished setting the power level,
press Edit L1 to close the open parameter.
To change the attenuation setting, press Incr Atten
or Decr Attn . Pressing these soft-keys changes the
attenuation in 10 dB steps.
Press Previous Menu to return to the ALC Mode
Menu display.
3-64 681XXC OM
NOTE
The set power level may not be
maintained when switching be
-
tween attenuator coupling modes.
LOCAL (FRONT LEVELING
PANEL) OPERATION OPERATIONS