HP 8920A, User Manual

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Chapter 5, AF Analyzer Screen
Block Diagram
Gain Cntl
AF Analyzer Gain Control specifies whether the AF Analyzer’s gain settings are
controlled automatically by AF autoranging (
Auto
), or by manual control (
Hold
).
The following settings are affected by AF autoranging:
• Input Gain
• De-Emp Gain
• Notch Gain
Operating Considerations
The normal mode of operation for the
Gain Cntl
field is
Auto
, allowing the
instrument to adjust the AF gain settings for optimum measurement accuracy.
This field can be set to
Hold
to disable the autoranging routines to increase
measurement speed. However, this requires you to select the desired gain settings
manually for each measurement.
NOTE: Decoder and Oscilloscope Interference: The AF autoranging function (
Auto
)
takes a small amount of time to determine the attenuation settings for the AF
Analyzer. If you are decoding an encoded signal, and your transmitter begins sending
encoded information the instant it transmits, the initial encoded information may not
be decoded during the autoranging process.
Use the
Auto
setting to establish the initial gain settings while the encoded signal is
first being decoded, and then select
Hold
during the decoding process to retain the
gain settings. The decoder should capture all encoded information the next time you
transmit the signal.
Input Gain
This field displays and selects the gain of the AF Analyzer’s input amplifier.
Refer to the
Gain Cntl
field information.