Stratovision - Early Tests

Early Tests

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, the Westinghouse television studios 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.

The aircraft received its originating signals from circular dipoles attached to a streamlined eight-foot (2.5 m) mast on top of the aircraft's vertical tail fin. The retractable 28 feet (8.5 m) long broadcasting antenna hung vertically beneath the aircraft. It was composed of a two-element turnstile array for video and a single-element circular dipole for sound transmissions.

The receivers, transmitters and necessary air-conditioning were all powered by the plane's engines using three 15 kVA, 500 Hz alternators. Without air conditioning the transmitters in the interior of the aircraft would have generated a temperature of 134 degrees Fahrenheit (57 degrees Celsius) with an outside air temperature of 25 degrees Fahrenheit (minus 4 degrees Celsius).

On 23 June 1948 the system's airborne transmitter rebroadcast the Republican National Convention, being held in Philadelphia, Pennsylvania, to the surrounding nine-state area during the 9 to 10 pm EDT time period. As part of the activity, a receiver was set up in a hall in Zanesville, Ohio, a small city on the outskirts of the broadcast area (to demonstrate to the invited newspaper reporters that the system was capable of reaching "small town and farm homes").

The tests were watched by many television viewers who sent in reception reports. From these reports it was calculated that Stratovision would require only eight relay planes to provide a transcontinental network and six additional planes to provide coverage to 78 percent of the United States. Mr. C.E. Nobles who was the head of Stratovision for Westinghouse said in his report:

"The major technical problems of the system have been solved, and the commercial development awaits only the crystallization of public demand for the expanded services offered by airborne broadcasting, application of the system by the radio industry to meet this demand, and the clarification of channel facilities available to make possible this application."