Protek A434L Operating Manual page 73

Trace Average: Indicates the average value of a single sweep over the user
setting frequency band.
Freq. Span: It is a user-defined frequency band. Changing the frequency
band doesn't affect the sweep time, but affects the calibration. Recalibration
is required if the frequency setting is changed.
Freq Band Info: The band name is displayed if the band is selected from the
band list stored in the instrument. If the user sets the start, stop, center or
span frequency manually, the band name will show "Custom"
Limit Line: Sets the upper limit value of the trace. The portion of the trace
that exceeds the limit line is displayed in red color. The captured trace by
using the Trace function does not display the exceeded portion of the trace
in different color.
Y scale unit: It is the measurement unit of the Y axis displayed for the trace.
Return Loss (dB)
VSWR
It is recommended to select high resolution trace
points only when measuring the wide frequency
band or a precise measurement is required.
The previously executed calibration is effective
even after the trace points change.
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