This page describes some general features of Audio Spectra.
Operation: The AF Spectra are operated by their two boxes at the left margin: "Flags" and "Line Plot".
The operation is self-explained and much the same as with the RF Spectra. A difference exists with the X-Zoom.
Zoom X: When moving this slider, the zoom point is at the left starting point of the spectrum, at zero Hz.
This might not always be desirable, for instance when inspecting details of the bare demodulated WFM spectrum.
The zoom point is simply selected by clicking at the point of interest in the spectrum. There, a small
yellow triangle appears indicating the frequency around which the spectrum is zoomed. The picture shows examples
of of an un-zoomed and a zoomed AF spectrum.
The zoom can be reset by clicking somewhere in the area at the left side of the line plot.
Bandwidth: The audio spectra of all demodulators are band-limited, both at the low and the high frequency, the bandwidth depending on
- Demodulator type
- Demodulator bandwidth
Modification: The spectra of the WFM and NFM demodulators are modified by their specific de-emphasis.
The WFM spectrum offers additionally the unmodified spectra of the whole demodulated bandwidth of up to 125kHz.