Stratovision, October 1945 Radio-Craft

Before comprehensive coaxial and optical cable or even microwave relay networks were available for commercial use, an experimental aircraft-based system was tested for broadcasting educational television and other messaging data. The "Stratovision" platform essentially provided a couple 20,000-foot-high antennas with a footprint covering hundreds of miles. This 1945 Radio-Craft magazine article entitled ,"Stratovision" was one of the earliest to report on plans to provide a coast-to-coast nationwide matrix of coverage as shown in the accompanying illustration. Two outfitted airplanes would be in the air within each region at all times to ensure redundancy and high quality service. Boeing B−29 Superfortress airplanes (the Enola Gay was a B−29) were used at least in part because they provided a human-friendly environment at high altitudes for long period of time.

The United States covered by 14 airplane stations. Detail of one plane's broadcast service territory, centering on Pittsburgh (inset).

Fourteen transmitters in planes 30,000 feet up can cover the United States with FM and television programs from metropolitan nets

A revolutionary new plan which - if found practical - will cut the number of steps for a transcontinental television relay from 100 steps to eight, was revealed recently by Westinghouse. The same plan would increase the coverage of a television or FM station from a 50-mile radius to more than 200 miles. The proposed new, system, originated by C. E. Nobles, 27-year-old engineer from Texas calls aviation in to help electronics, and has been given the name of Stratovision.

The Stratovision system simply puts the antenna and transmitter in an airplane flying in lazy circles 30,000 feet above the earth, out of sight of human eyes. The short waves sent out from this airborne antenna would blanket the earth's surface like a great inverted ice cream cone; covering an area 422 miles across or equal to about the combined area of New York, Pennsylvania and New Jersey.

Reception of Stratovision broadcasts would be practically free from interference and distortion, caused normally by reflected ground waves and the numerous amplifications or relaying stages required by any previously proposed system to carry television and FM broadcasts over a comparable area.

As the height of a television or FM antenna is increased, the amount of power required to deliver a usable signal to a receiver is sharply reduced. To provide a useable signal throughout a 422-mile wide receiving area covered by a plane-borne transmitter 30000 feet in the sky, would require only one-fiftieth as much power as is needed by a 50 kilowatt transmitter on the ground covering an area only 100 miles in diameter.

The Stratovision system would employ a low-powered ground transmitter to send television and FM broadcasts to a specially-designed high-altitude plane circling slowly overhead. The plane would be equipped with receivers and transmitters for re-broadcasting these programs to the earth. As now conceived, the plan would employ four television and five FM transmitters on each plane.

A coast-to-coast network for relaying television and FM programs from plane to plane between New York and Hollywood would simply require stationing, eight such stratosphere planes above strategic areas spanning the continent. To provide comparable service by ground installation, it is estimated, would require approximately 100 costly relay towers and hundreds of transmitters; or a coast-to-coast coaxial cable network which would cost at least $100,000,000.

The eight planes in the Stratovision relay system would fly over New York, Pittsburgh, Chicago, Kansas City, Curtis (Nebraska ), Leadville (Colorado) , Salt Lake City and Los Angeles, linking logical talent centers in New York and Hollywood. By adding six more planes over Durham (North Carolina), Atlanta, Memphis, Dallas, Sacramento and Portland (Oregon), It would be possible to provide Stratovision coverage for 51% of the nation's area and 78% of its population.

Programs would be originated in conventional ground studios connected with plane transmitters by a special beamed-type ultra-shortwave radio link, much like those used in radar. Similarly beamed plane-to-plane connections would be employed to form the nation-wide high-altitude relay network.

The advantage of mounting several transmitters in the same plane is greater choice of programs and economy of operation, since each transmitter would function as a separate station.

Contributing to economy of the system is the fact that as the height of a television or FM antenna is increased, the amount of power required to deliver a useable signal throughout its line-of-sight area is sharply reduced. One kilowatt of power will be sufficient to provide a useful signal throughout the 422-mile range of an antenna located 30,000 feet in the air. Thus power to operate all nine transmitters and all monitoring and relaying equipment can be provided by each plane's engines.

Still another advantage of the plan - one of special interest to engineers concerned with television and FM relay systems - is the fact that Stratovision will drastically reduce distortion resulting from repeated amplification.

Each repeater station adds its quota of distortion to a television or FM program, and any ground system, because of its many repeaters, would build up a great amount of accumulated distortion. By cutting the number of relay stations to a minimum, such distortion would cease to be an important factor.

The system would bring not only television and FM to millions of new viewers and listeners, its proponents claim, but, in addition, would greatly improve these services for audiences - old and new.

Best reception requires that the antenna of each receiver have directional characteristics and be pointed directly toward the transmitter antenna. This means that, for best results, the antenna for each ground receiver must be movable, and each receiver equipped with a mechanical device for bringing its antenna to bear exactly on the transmitter of each new station from which a program is desired.

Stratovision eliminates this need since one fixed antenna installation at the receiver can be beamed so as to cover the entire small-circle course of one plane flying at 30,000 feet, keeping it constantly in "view." Such an installation will insure access at all times to all programs of every station operating a transmitter in that plane.

Another distinct improvement in service would result from Stratovision's high-altitude operation and the fact that its antennas will be in constant motion. This is in the matter of "ghosting," the annoying out-of-register viewing which occurs when receivers pick up programs by two different waves - one arriving by the most direct path between the transmitter and the receiver, the other by a reflected path.

Stratovision reduces the possibility of such reflection because its high-altitude operation will enable receiver owners to point antennas into the air - above mountains and other ordinary sources of ground reflection.

In addition, movement of the plane will make any reflection which might occur of only very brief duration - so brief, perhaps, as to be undetected by the eye.

By cutting costs, it is hoped, the Stratovision system will place television and FM transmission on a sound and economically justifiable business footing for the first time. It would preclude the tedious city-to-small-town growth necessarily envisioned by all earlier plans, and it promises to make both services available to isolated rural homes which could not expect them for years - if ever - by any other system.

Early experiments show that the system is completely workable in any of the several television and FM frequency allocations which were recently announced by the FCC. Operation actually improves in the higher frequencies. This means that the system may hasten the day of practical

According to high officials of the Glenn L. Martin Co., Stratovision presents no radical problems of aircraft design or operation.

Four planes would be assigned to each broadcast location. Two would be in the air at all times - one handling programs, the other standing by to take over in case of any emergency. Planes would fly over the center of assigned areas and relief planes would be sent aloft sufficiently in advance of shift changes to insure uninterrupted operation. The 30,000 foot level is tentatively proposed as giving the widest practical range, and as being well "above the weather" which might cause problems at lower altitudes.

"One of the most unusual features of the Stratovision system," pointed out William K. Ebel, Martin's vice-president, "is its need for a slow airplane. After years of striving for progressively greater speed in all our design and construction it is intriguing to be asked to build a huge heavy-load plane to fly only fast enough to remain safely aloft at very high altitudes. Yet by the very nature of its operation, that is all the system requires."

In addition to its four high-altitude planes, each broadcast location would have a smaller plane equipped to act as a flying remote "pickup unit. This plane would be available to cover any special event or emergency within the location's 103,000 square mile area, relaying television and FM programs to the parent plane for local broadcast or for nationwide network presentation.

StratovisionOctober 1945 Radio-Craft

Stratovision
October 1945 Radio-Craft