OPERATION
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Demod FFT/Subcarrier Demodulation
Subcarrier demodulation is a means of decoding a second “piggy backed” signal carried on a normal
transmitted radio signal. Subcarrier demodulation is sometimes referred to as double demodulation.
Subcarrier signals are used for transmitting a number of things including stereo audio information,
metadata, color information, and even audio for video signals. While performing an audio or video
demodulation, to demodulate an audio sub carrier:
1. Demodulate a known video or audio signal. In order to demodulate a subcarrier, you must
already be tuned to and demodulating a main carrier.
2. From the Analyze Mode Menu, select Demod or press F1 to enter the Demod Sub-menu.
3. From the Demod Sub-menu, select Subcarrier or press F2 to enter the Subcarrier Sub-menu.
4. Select the Demod FFT icon. A new tabbed window, Demod Spectrum, will appear displaying a
frequency domain representation of the demodulated signal. If there are any subcarriers
present, they will be easy to detect using the demodulated spectrum. In order to tune
subcarriers you must open the Demod Spectrum window. Select the Demod Avg icon to turn on
an average trace for the Demod Spectrum. This may make it easier to detect subcarriers.
Subcarrier
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