HP 8711C User Manual page 233

Calibrating for Increased Measurement
Accuracy
Choose an Appropriate Calibration Method
This method of calibration is only necessary when trying to achieve
maximum dynamic range (> 100 dB). A response and isolation calibration
prompts you to connect loads to both ports and then to connect a through
cable. These standards are measured across the frequency band you have
defined, using the number of points you have defined. These measurements
are used to remove systematic errors caused by frequency response and
crosstalk.
This method of calibration is superior to the standard response calibration.
This calibration prompts you to connect four measurement standards: an
open, a short, a load, and a through cable. The analyzer measures each
standard across the frequency band you have dehned, using the number of
points you have defined. The measurements of these standards are used to
remove systematic errors caused by frequency response and source match.
Transmission
Widening the frequency span after performing any of these calibrations will
Calibration
invalidate them, and restore the default calibration. You may narrow the span
Interpolation
and the analyzer wiLl interpolate correction for the narrower span.
Note that after you have calibrated, a "C" appears in the upper right hand
corner of the display. This "C" indicates that a user-defined cal is in use. If
you change to a narrower span, note that the "C" changes to "C?", indicating
the analyzer is now interpolating between calibrated measurement points.
The "C?" notation also appears when other system parameters, such as
power, number of points, or sweep time, have changed.
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