Preamplifier Control (Opt 235); How To Control The Preamp; Check For Compressed Measurements; How To Check For A Compressed Measurement - Keysight A Series User Manual

SA (Spectrum Analyzer) Mode (Option 233–Mixed Analyzers)
SA Mode Settings

Preamplifier Control (Opt 235)

When very low-level signals are analyzed, an internal preamplifier can be used
to boost the signal level by approximately 22 dB. The gain of the preamp is
NOT adjustable. The displayed signal level is automatically adjusted for the
increase in system gain.

How to control the Preamp

By default, the preamp is OFF.
— Press Scale/Amptd.
— Then

Check for Compressed Measurements

Compression occurs when too much power into an amplifier causes it to no
longer amplify in a linear manner. When too much power goes into the
FieldFox RF Input connector, the amplifiers in the SA receiver compress and
signal power will not be displayed accurately. This can occur even if
Range
might be compressed. Increase the RF Attenuation value to prevent the SA
receiver from being compressed.

How to Check for a Compressed Measurement

1. Using a marker at the signal peak, make note of the signal power level.
2. Increase the RF Attenuation level by 5 dB.
174
Preamp ON OFF
ON, PA is shown to the left of the graticules on the display.
is not displayed because devices other than the ADC, such as the mixer,
— If the signal level does NOT change, then NO compression exists.
This indicates that the signal is in the linear region of the FieldFox
receiver.
— If the signal level DOES increase, then the receiver was compressed.
Set the RF Attenuation value at the setting when further increases
no longer result in an increase in the displayed power level.
The underlined setting is the current setting. When
Keysight N9927-90020 User's Guide
ADC Over