Spectrum Reference curve
See also: Spectrum Lab's main index ,
settings dialog .
Usage of the spectrum reference
The spectrum reference can be displayed as curve in an overlay of the
spectrum graph. The reference data
can be taken from a spectrum which has been recorded previously, it can also
be saved as and loaded from a file (as a TEXT file). The controls for the
"Spectrum Reference" are explained later.
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The spectrum reference controls are located on a special tab in the
if checked, the reference spectrum is shown in the graph as an "overlay".
The visibility can also be turned on and off through an
Used to define the color of the reference spectrum (if visible)
If checked, the reference spectrum will always be subtracted from the currently
displayed spectrum (in the spectrum graph and on the waterfall).
This feature can be used to detect "slow changes" if used together with the
Copy from current spectrum
Click this button if you want to use the actual spectrum as a new reference.
The new reference will not be saved as a file automatically (you can save
it from the "File" menu). The same function can be invoked as an
interpreter command too.
Copy from long-term average
Similar as above, but this function copies the reference curve from the
spectrum (instead of from the most recently calculated spectrum).
Notes and hints:
To generate a "smooth" reference, use a very slow waterfall scroll interval
in combination with the "optimum waterfall average" (in the "Spectrum display"
menu), or turn on the long term average and copy the reference from there
(after a sufficiently long time of integration, when the curve is reasonably
For example, feed noise into your receiver and you will get the frequency
response of the IF filters (etc) which you can save as a reference file (in
the main menu under "File").
The reference can be saved as a text file (extension usually ".REF"). You
can modify such a file with a text editor, or with a spreadsheet program,
or with the author's "Curve Editor". The latter is a tiny utility to view
and edit array data stored in textfiles. Search the net for "DL4YHF's Ham
Radio Homepage" or "DL4YHF Curve Editor" to find it.
The interpreter command
"spectrum.save" uses the same
text file format as used for the reference curve.
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The following commands (and functions) for SL's command
interpreter can be used to control the spectrum reference:
Picks the "curve" for the reference spectrum from the current spectrum in
the main analyser, like the button "Copy From Current" on the spectrum reference
Optionally, the source (channel) can be specified for this command, like:
Other possible sources (spectrum analyser channels) are listed
Turns the visibility of the spectrum reference in the spectrum graph on (1,
or any non-zero expression) or off (0, zero). For example, the
sref.visible = ! sref.visible toggles the visibility
of the spectrum reference.
Loads the spectrum reference (curve) from the specified file.
Saves the spectrum reference (curve) as a textfile, from which it can be
See also: Overview of interpreter
numeric expressions .
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