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In FM stereo broadcasting, a pilot tone of 19 kHz is used to indicate that there is stereophonic information on a subcarrier at 38 kHz (19×2, the second harmonic of the pilot). If no pilot tone is present, then the 38 kHz (more often 39 kHz) subcarrier is not stereophonic information, and is used for other purposes. A guard band of ±4kHz (15-23 kHz) is used to protect the pilot tone from interference from the basebandIn telecommunication, the term baseband has the following meanings: 1. The original band of frequencies produced by a transducer, such as a microphone, telegraph key, or other signal-initiating device, prior to initial modulation. In transmission systems, audioAudio can mean: sound that can be heard electronic or other signals of frequencies audible to humans (about 20--20,000 Hz) broadcasting or reception of sound high-fidelity sound reproduction sound recording and reproduction in general "I hear" in the Lati signal (50 Hz-15 kHz), and from the lower sidebandIn radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing energy as a result of the modulation process. While all forms of modulation have sidebands by definition, it is most commonly discusse of the stereo subcarrier (23-53 kHz). The third harmonic of the pilot (19×3, or 57 kHz) is used for Radio Data SystemRadio Data System or RDS is a standard for sending small amounts of digital information using conventional FM radio broadcasts. The RDS system standardizes several types of information transmitted, including time and station identification. RDS is widely.
In AM stereoAM stereo refers to any of a number of mutually- incompatible techniques for broadcasting two-channel audio in the mediumwave band in a manner that is compatible with receivers designed for standard amplitude modulation. There are two main classes of syst, the bandwidthAnalog Bandwidth is the width, usually measured in hertz, of a frequency band f f. It can also be used to describe a signal, in which case the meaning is the width of the smallest frequency band within which the signal can fit. It is usually notated B, W, is too narrowNarrowband narrow bandwidth refers to a signal which occupies only a small amount of space on the radio spectrum the opposite of broadband or wideband. This is entirely relative to what is being described; for example, an FM broadcast station takes up 150 to accommodate subcarriers, so the modulationFor the musical use of "modulation", see modulation (music . Modulation describes a range of techniques for encoding information on a carrier signal typically a sine-wave signal. A device that performs modulation is known as a modulator . Modulation techn itself is changed, and the pilot tone is subsonic (below the normal hearing range, instead of above it).
In color television, the color burst placed between each video field is the pilot signal to indicate that there are color subcarriers present.
In the NTSC television system, a pilot tone of 15.734 kHz is used to indicate the presence of MTS stereo.
Note: Sometimes it is necessary to employ several independent pilot frequencies. Most radio relay systems use radio or continuity pilots of their own but transmit also the pilot frequencies belonging to the carrier frequency multiplex system.
Source (in part): Federal Standard 1037C and MIL-STD-188
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