Freedom R8100 SERIES, Operator'S Manual

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|Spec-Ref| (lin) – Displays the logarithm of the absolute value of the difference of the Display Mode
spectrum in volts² minus the reference trace in volts². Note: Although the absolute value of the difference
avoids logarithm of negatives, it has the side-effect of increasing the apparent noise power.
Spec+Ref (lin) – Displays the logarithm of the sum of the Display Mode spectrum in volts² plus the
reference trace in volts².
Figure 2.2.4.1-1 Trace Math Display
Set Reference Trace
Copies the current spectrum trace (white) and shows it in a static trace (cyan) behind the spectrum trace.
The trace is copied from what is currently shown, which is after any Display Mode processing as well as
Trace Math computations. Therefore, ensure that both of those settings are set appropriately (i.e. Trace
Math is None); setting the reference when Trace Math is active may yeild incoherent results. Setting
Display Mode to Average minimizes effects of a low level / high variance signal such as the noise floor.
This static trace is used for computations when a Trace Math equation is specified; and may simply be
viewed even when one is not. It can be hidden by selecting Trace Math None. Note: System changes that
may invalidate the reference trace include port, amplification, attenuation, frequency, span, temperature,
and calibration.