by Peter Q. George
Educational stations KS2XGA, channel 72 and KS2XGD, channel 76 were the stations of MPATI, The Midwest Program on Airborne Television Instruction. MPATI was a non-profit organization of educators and television producers who pioneered efforts to transmit instructional television to a wide audience before the advent of cable and satellite.
The MPATI project began as an experiment in 1959 and began actual telecasting in 1961, funded through the combination of a $4.55 million grant from the Ford Foundation and other corporate and private gifts. The stations were located inside two DC-6AB aircraft based at the Purdue University Airport in West Lafayette, Indiana. The aircraft would fly for six to eight hours at an altitude of 23,000 feet (about 4½ miles up) and take a 20-minute figure-eight station centered over Montpelier, Indiana. From this height, the coverage area was approximately 200 miles in diameter, including the Detroit and Chicago metropolitan areas.
The origins of the MPATI project date back to the mid-1940s. The line-of-sight problem that only allowed broadcasters to send signals from ground-based receivers plagued early television. Yet, in 1944, Westinghouse engineer Charles Noble discovered a solution to this problem. A plane flying at an altitude of 25,000 feet could "see" with a radius of 225 miles, many times more than conventional ground transmitter sites could. Noble's idea was to equip planes with broadcast equipment that would allow them to transmit signals to a larger audience. It was called "Stratovision".
The FCC freeze on television channel allocations in 1948 ended Westinghouse's experiments with Stratovision, thus shelving the idea until the late 1950s. By then, television broadcasting had indeed changed. Commercial television had outgrown the idea Stratovision had been designed for. Television networks had already sprung up and connected local stations from coast-to-coast with duplicated programming.
Educational television, on the other hand, still lacked the means to send duplicated programming to a large area. In 1958, Westinghouse contacted Philip Coomb, executive director of education for the Ford Foundation, who was very enthusiastic about using Stratovision for educational purposes.
Programming from the planes was completely pre-recorded, produced by Purdue University. Taped classroom instruction, test patterns, ID slides with canned music behind the video ... all were completely on tape. (MPATI spokespersons said they were "amused" that they had to continually explain that the teachers really weren't cramped up in the plane all day waiting their turn in some tiny aerial studio.) The television equipment -- videotape decks and such -- and the two UHF transmitters were powered by a gas-turbine generator located in the aft end of the fuselage. The 40-foot UHF antenna, lowered under the bottom of the plane once the plane was "on station", was gyroscopically stabilized to ensure that the antenna was always aligned toward the center of the earth.
MPATI was granted seven experimental authorizations on December 12, 1959, all licensed to Purdue: KS2XGA on channel 72 with 28.2kW; KS2XGB on channel 73 with 12kW; KS2XGC on channel 75 with 12kW; KS2XGD on channel 76 with 12kW; KS2XGF on channel 34 with 12kW; KS2XGG on channel 53 with 12kW; and KS2XGH on channel 59 with 12kW. Only the channel 72 and 76 authorizations were used, each with 1kW ERP (channels 53 and 59 were originally intended for uplinking programming from the University to the planes); MPATI was to have begun operation on January 30, 1960, using half-bandwidth transmissions allowing for an additional four signals to be transmitted on channels 75 and 76, with the full-bandwidth signals on channels 72 and 73. According to an article in Broadcasting on December 26, 1960, the split channels were to use a 441-line scan rather than the conventional 525 lines and 24 frames-per-second rather than 30, which would have required special receivers in classrooms designed to receive the unusual transmissions. However, the half-bandwidth scheme was scrapped by the time the service finally got "off the ground" in the fall of 1961, as was the uplink via the additional UHF allocations. (We do not know what use the channel 34 allocation was intended for.)
In addition, non-commercial educational WTTW/11 in Chicago carried the morning MPATI programming; WXIX-TV/18 Cleveland offered to do likewise but was rejected because of its commercial status. Ground-based translators were also authorized for retransmission of the MPATI signals in Detroit and Chicago (channels 79 and 83 in both cities) in 1962 and in Cleveland (channels 81 and 83) in 1963.
In theory, the idea was sound. In practice, however, the idea was not economically viable. In 1963, the project relied on membership fees from the various school districts throughout the Midwest who used MPATI's taped instructional courses. However, not everybody paid the fees. Since it was an open system, anyone with a UHF-capable television set could tune in. (Perhaps they shouldn't have scrapped the half-bandwidth transmission scheme.)
At the beginning of 1963, MPATI took the bold step of requesting FCC rulemaking to give them six UHF channels on a permanent basis (all the even channels starting with channel 72), pre-empting their use in the states of Illinois, Indiana, Kentucky, Ohio, Michigan and Wisconsin for other television purposes. The hearings for that rulemaking went on until mid-1964 (the "big gun" in the room was Westinghouse, which as MPATI's equipment supplier certainly had a vested interest in the outcome, but they made matters worse when they proposed a six-channel service using 33 planes and 18 UHF channels -- including all of those reserved for use at that time by translators -- at the end of 1963).
The major stumbling block in MPATI's plan came, ironically, from the National Association of Educational Broadcasters, which submitted an engineering study which showed 50 UHF channels -- likely to come from non-commercial educational reserved allocations under the circumstances -- would have to be deleted from the FCC's allocations table because of their technical relationship to the frequencies of the channels above 70. The Association for Maximum Service Telecasting, made up of commercial television stations, also testified that their research showed as much as 40% of the UHF television spectrum in the area would be unusable by ground-based transmitters under the plan. (The FCC's engineers estimated the number of ground assignments "wiped out" would total between 750 and 1,110 and wreak havoc with agreements for assignments in Canada and Mexico.)
The full Commission denied the MPATI request on May 12, 1965. As a result, MPATI ended the Stratovision broadcasts in 1966 and switched to ITFS (Instructional Television Fixed Service, in the 2500 MHz band, which had been authorized as a new service by the FCC in July 1963) as KDI-99, ended production, turned in the planes and the UHF licenses and operated four local area-only ITFS channels. (It is noted that the FCC was amenable to re-licensing the airborne transmitters in the ITFS band; no documentation is available to explain why that option was not pursued.) MPATI continued to serve as a lending library to its member schools elsewhere and eventually completely dissolved in 1973, after a long protracted suit with Westinghouse. However, MPATI and Westinghouse did settle amicably after MPATI's assets were liquidated.
Stratovision itself got a temporary reprieve in 1966 when the technology was used to provide television service to South Vietnam on channels 9 (programs for U.S. servicemen) and 11 (programs from Saigon in Vietnamese), plus radio stations on AM 1500 and FM 99.9.
A shorter version of this article originally appeared in the author's "UHF Morgue" at his former RadioDXer site and is republished here with his permission. Information for the original article was provided by Kristi Mashon and Karen King of The University of Maryland Libraries and by Bucky Terranova. Reformatting and additional information by K.M. Richards. Photographs of the exterior and interior of the MPATI DC-6 were obtained from the University of Maryland Hornbake Library Special Collections.
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