Editing Pilot signal (section)

=== FM Radio ===
[[Image:Frequency Spectrum FM-Radio.gif|thumb|right|Spectrum of an FM broadcast signal. The pilot tone is the orange vertical line on the right of the spectrogram.]] In [[FM stereo]] broadcasting, a '''pilot tone''' of 19 [[kHz]] indicates that there is [[stereophonic]] information at 38 kHz (the second [[harmonic]] of the pilot tone). The receiver doubles the frequency of the pilot tone and uses it as a frequency and phase reference to demodulate the stereo information.

[[Image:PilotSignal.png|thumb|right|Radio Spectrum of an FM Radio Broadcast channel as decoded by SDRConsole application. Shows the Pilot Signal at 19kHz, Mono, Stereo and RDS spectrum blocks.]]

If no 19 kHz pilot tone is present, then any signals in the 23–53 kHz range are ignored by a stereo receiver. A [[guard band]] of ±4 kHz (15–23 kHz) protects the pilot tone from [[Adjacent-channel interference|interference]] from the [[baseband]] [[Audio frequency|audio]] signal (50 Hz–15 kHz) and from the lower [[sideband]] of the [[double sideband]] stereo information (23–53 kHz). The third harmonic of the pilot (57 kHz) is used for [[Radio Data System]]. The fourth harmonic (76 kHz) is used for [[Data Radio Channel]].