Amateur television
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Amateur television (ATV) is the hobby of transporting broadcast-quality video and audio over radio waves allocated for amateur radio using the broadcast standards of NTSC in North America and Japan, and PAL or SECAM in Europe and elsewhere, using the full refresh rates of those standards. It also includes the study of building of such transmitters and receivers and the propagation between these two. ATV is an extension of amateur radio.
In North America, broadcasts are typically sent from repeaters on four UHF channels below the UHF TV broadcast band (air channels 14 to 69). These can be received on a cable-ready NTSC-format TV or set-top box tuned to cable channels 57 to 60 (420-444MHz). Individual channels (with center frequency for video and audio) are:
- 57: 420-426MHz (421.25 video, 425.75 audio)
- 58: 426-432MHz (427.25 video, 431.75 audio)
- 59: 432-438MHz (433.25 video, 437.75 audio)
- 60: 438-444MHz (439.25 video, 443.75 audio)
- ...
- (66: 470-476MHz, over-the-air channel 14)
Typically frequency modulated TV is used on frequencies above 1200MHz (1.2GHz), where there is enough bandwidth for such wideband transmissions. This is often used as a repeater's input frequency, with output being standard VSB on the four channels listed above. An ATV repeater may also broadcast a noncommercial TV network which does not include music (a U.S. requirement also part of amateur radio). U.S. stations often transmit NASA TV while they are not in use, especially if there is currently a Space Shuttle mission.
In Europe, recent experiments have been done with digital modes following widely-adopted DVB-S and DVB-T standards. Currently, digital ATV modes have not been approved by the FCC in the U.S.
See also: SSTV