mpati

TV from the Sky (in the 1960's)

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The Broadcasting Yearbook has always listed every licensed radio and TV transmitter in the United States, Mexico and Canada. Also listed were experimental TV stations. There were many of those held by various companies and universities all with the express purpose of finding new ways to broadcast and new equipment to do the broadcasting.

For Purdue University in West Lafayette, Indiana, there were these licenses listed: KS2XGA channel 72 (used for MPATI), KS2XGB channel 78, KS2XGC channel 75, KS2XGD channel 76 (used for MPATI), KS2XGE channel 41, KS2XGF channel 34, KS2XGG channel 53, and KS2XGH channel 59. For the younger people out there the UHF band used to go up channel 83.

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Long before there were satellites broadcasting programming to our homes, there was this idea to broadcast programming from airplanes.

This information is from the same book that had the information about the purpose of test patterns:

Stratovision was a television system that was being developed by the Westinghouse company. The TV transmitter was placed in an airplane and the program were broadcast from the airplane while it was inflight. The transmitter's coverage area is increased by virtue of the increased line-of-sight distance to the horizon. At an altitude of 20,000 feet, a coverage radius of 50 miles is possible, which is about the distance reached by the average transmitter on the ground. At an altitude of 30,000 feet, a coverage radius of 210 miles is possible, and at 50,000 feet, about 300 miles is possible.

Approximately 20 kilowatts of power are needed at a ground station to transmit a usable signal a distance of approximately 50 miles, whereas only one kilowatt of power will deliver the same usable signal 200 miles from a transmitter located in a plane flying at 30,000 feet.

A stratovision network of eight planes could link New York and California, as compared to the 100 ground relays necessary to fulfill the same purpose. Fourteen planes carrying transmitters could supply television programs to 78% of the population of the United States. (see map top)

The proposed system would need airplanes to take off at four hour intervals, remaining at 30,000 feet for eight hours each. This would keep a plane in the air at all times. A standby plane would always accompany the one in use and be ready to take over in case of airplane or transmitter trouble. At each stratovision area, four planes would be required so that while two were flying the other two would be undergoing maintenance or repairs. (Westinghouse plane middle picture)

The transmitting plane would fly in circles at about 30,000 feet. The program would originate on the ground and be transmitted to the plane by a small ground transmitter and directional antenna system. It was thought that the planes could operate economically if the planes were large enough to carry two or more transmitters, that way several stations could splite the cost.

[yes, the book did mention satellites, but back then it was merely an idea. the airplane seemed more practical.]

The only actual stratovision service that I am aware of was the Midwest Program on Airborne Television Instruction (MPATI) in Indiana. (picture bottom)

This service was broadcast four days a week from either a DC-6 or DC-7 (the source material is not clear) flying at 20,000 feet over north central Indiana, using channels 72 and 76 in 1961. The project was a joint effort by Indiana and Purdue Universities that broadcast programming on videotape directly from the plane. The target audience was some 5,000,000 students in 13,000 schools and colleges.

The plane carried two videotape machines (using the old 2 inch wide tape...this was way before videocassettes), two UHF TV transmitters, a rack of the day's videotapes, and the associated video equipment.

An Indian Head Test Pattern was displayed for five minutes between programs, but without any indication to which channel was which. Since analog UHF TV tuners on the receiving sets were not accurate a school using the educational service could not readily tell where they were tuned unless they were careful and chose the proper channel prior to the start of the telecast. (For example, rocking the dial back and forth to find the two test patterns that did not carry channel numbers. Channel 72 would have been the first one on the left and channel 76 would have been the second one on the right.)

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