Attenuator
Decoupling
In 681XXBs equipped with option 2 step attenu-
ators, the ALC and attenuator work in conjunction
to provide leveled output power down to –120 dBm.
In the normal (coupled) leveling mode, when the de-
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 control the ALC level and attenuator setting sepa-
rately by decoupling the step attenuator from the
ALC. The ALC mode menu lets you select attenu-
ator decoupling.
At the ALC Mode menu, press
Atten Menu
. The At-
tenuator 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
control key or rotary data knob or enter a new value
using 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.
NOTE
The set power level may not be
maintained when switching be-
tween attenuator coupling modes.
LOCAL (FRONT
LEVELING
PANEL) OPERATION
OPERATIONS
3-52
681XXB OM
