Amateur Television

Amateur Television (ATV) sends full-motion video with sound from one ham station to another, much like broadcast TV. It is often called fast-scan ATV to set it apart from SSTV, which sends one still picture at a time through a voice channel and takes a minute or two to do it.

Moving pictures need a lot of room, so ATV lives on 70 cm and the microwave bands, where image signals are allowed and Technicians have full privileges. The ARRL band plan sets aside 6 MHz-wide slots on 70 cm for it, with video carriers at 421.25, 427.25 and 439.25 MHz, and lists more ATV channels on 33 cm and 23 cm.

Analog ATV looks like old over-the-air television, with snow creeping in as the signal weakens. Digital ATV (DATV) borrows satellite TV standards such as DVB-S2 and fits a sharp picture into far less spectrum; the band plan mentions 2 MHz-wide digital channels on 33 cm. A digital picture stays clean until the signal gets too weak, then it freezes or breaks into blocks.

ATV repeaters work like voice repeaters, only for pictures. The 70 cm band plan includes a repeater input slot at 439.25 MHz, and a well-placed repeater lets stations across a metro area see each other. ATV is also handy for sending a live view from an event back to a club station.

DATV has reached space, too. The geostationary satellite QO-100, launched in 2018 and parked at 25.9° East, has an 8 MHz-wide transponder for digital TV, with an uplink near 2.4 GHz and a downlink near 10 GHz. Its coverage runs roughly from Brazil to Thailand, which leaves out North America. The International Space Station carries a DATV transmitter called HamTV on 2395 MHz, used for live video during some school contacts; check the ARISS HamTV page for its current status.

You may identify with your callsign shown on screen, as well as by voice or CW. ATV often means amplifiers and high-gain antennas on UHF and microwaves, which concentrate RF energy. Keep people out of the beam of a transmitting antenna, never look into a dish feed while it is transmitting, and do the RF exposure evaluation the rules require.

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