Stratovision

Stratovision was an airborne television transmission relay system from aircraft flying at high altitudes. In 1945 the Glenn L. Martin Co. and Westinghouse Electric Corporation advocated television coverage of small towns and rural areas as well as the large metropolitan centers by fourteen aircraft that would provide coverage for approximately 78% of the people in the United States This system has been used for domestic broadcasting in the United States, and used by the U.S. military in Vietnam and other countries.

Because the broadcasting antenna for Stratovision is usually hung beneath the aircraft in flight, it naturally has a great command of Line-of-sight propagation. Although transmission distances are dependent upon atmospheric conditions, a transmitting antenna 30,000 feet (9 km) above the Earth's surface has a line of sight distance of approximately 211 mi (340 km).

A Stratovision 25 kW transmitter operating from 30,000 feet (9 km) at 600 MHz will achieve a field intensity of 2 millivolts per meter for a 30-foot (9 m) high receiving antenna up to 238 miles (383 km) away from the aircraft.

Stratovision tests were undertaken between June 1948 to February 1949. The first phase was undertaken by the Glenn L. Martin Co. and Westinghouse Electric Corporation using a twin-engine PV-2 aircraft flying at 25,000 feet (7.6 km) that transmitted with 250 watts on 107.5 MHz and 5 kW on 514 MHz at Baltimore, Maryland so that recordings could be made at various locations ranging from Norfolk, Virginia to Pittsburgh, Pennsylvania and Boston, Massachusetts.

The second phase of testing was undertaken by these companies using a stripped-down B-29 Superfortress flying at 30,000 feet (9.1 km). The plane was equipped to receive a relay transmission from WMAR-TV in Baltimore, which was then relayed over a 5 kW video transmitter and a 1 kW audio transmitter for reception on 82-88 MHz with a television set tuned to Channel 6.

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