Check For Compressed Measurements - Keysight N9912A User Manual

When too much power is present at the RF IN port,
the FieldFox screen. This does not necessarily mean that damage has occurred, but
that the measurement is probably compressed.
When high power levels are present at the RF IN connector, internal attenuation can
be switched in to keep the FieldFox receiver from compressing. At extremely high
power levels, use external attenuation to protect the internal circuitry from being
damaged.
WARNING
The displayed power level is automatically adjusted for RF Attenuation. As the
attenuation value changes, the displayed power level should NOT change.
How to set Attenuation
The default Attenuation setting is 10 dB. This value can be changed from 0 to 31 dB
in 1 dB steps.
 Press Scale/Amptd .
 Then


#Atten xx dB is shown at the top of the screen. (#) means manual setting.
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 IN
connector, the amplifiers in the SA receiver compress and signal power will not be
displayed accurately. This can occur even if
Increase the RF Attenuation value to prevent the SA receiver from being compressed.
74
The FieldFox can be damaged with too much power.
RF Damage Level: +27 dBm
DC Damage Level: ±50 VDC
RF Atten Auto Man.
RF Attenuation is set by adjusting the Reference Level. As the Reference
Auto
Level is lowered, for example from –10 dBm to –30m dB, the FieldFox assumes
that you are looking at low-level signals. The RF Attenuation value is automatically
lowered in 5 dB steps to allow low-level signals to be viewed. The RF Attenuation
value is never automatically lowered below 5 dB.
RF Attenuation is set manually. Enter a value using the numeric keypad, the
Man
▲|▼ arrows, or the rotary knob. Values less than 5 dB must be typed using the
numeric keypad. Then press Enter
Preamp ON OFF
is shown to the left of the graticules on the display.
PA
The underlined setting is the current setting. When ON,
ADC Over Range
appears on
ADC Over Range
is not displayed.
FieldFox User's Guide