HP 8920A, User Manual

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475
Chapter 17, RF Analyzer Screen
Field Descriptions
IF Filter
This field selects the desired IF Filter bandwidth for modulated signals being
analyzed.
Input Atten
Input attenuation sets the amount of input attenuation for the RF IN/OUT and
ANT IN connectors. This function controls two settings:
• The upper field determines if you want the instrument to set the attenuation automati-
cally (
Auto
), or if you want to set the value manually (
Hold
).
• The lower field displays the present attenuation value, and it is used to set the desired
attenuation level when the upper area is set to
Hold
.
NOTE: Oscilloscope and Decoder Interference. After a signal is input, the RF autoranging function
(
Auto ) takes a small amount of time to determine the required input attenuator setting. If your
transmitter begins sending encoded information the instant it transmits, the initial encoded
information may not be decoded during the autoranging process. The same situation can arise
when trying to display the first part of the demodulated signal on the Oscilloscope.
When decoding a signaling sequence using the decoder, or when trying to
capture the initial modulation waveform of a signal on the Oscilloscope, set the
upper field to
Hold
and set the lower field to an appropriate level for the signal
being decoded (start with 40 dB).