8163A/B, 8164A/B, 8166A/B User’s Guide 233
Setting Attenuation and/or Power Levels 8
How to Use the Power Control Feature
81576A/77A Attenuator modules incorporate Power Control functionality
that automatically corrects for power changes at its input to maintain your
desired output power.
This feature is designed to compensate, for example, for output power drift
by the source.
When Power Control is On:
•If P
actual
deviates by more than 0.1 dB from your desired P
SET
value,
the Attenuator module automatically restores P
SET
at the maximum
possible filter transition speed of 12 dB/s.
• Input power is measured using your set Averaging Time.
• To avoid ‘hunting’, and consequent wear on the filter motor mechanism
in response to an unstable source, for differences between P
SET
and
P
actual
greater than 0.01 dB, but less than 0.1 dB, P
SET
is updated
approximately every 30 s.
• The Attenuator module does not respond to a power difference of
0.01dB or less. Such a change is regarded as noise.
• If the attenuation is driven beyond 0 dB, Exp (“Excessive Power”) is
displayed. There is now insufficient input power for the Attenuator to
maintain your desired P
SET
.
Power Control On/Off
To enable or disable Power Control, select the [Pwr Ctrl] parameter.
When Power Control is On the Attenuator’s status display includes ‘PC’.
The Menu item <Pwr Control> is functionally equivalent to the
[Pwr Control] parameter.
Attenuator Menu Options
81570A/71A/73A Menu Options
Press the [Menu] softkey to display the window shown in Figure 141 on
page -234.
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