FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1945
1945 - 1775.PDF
FLIGHT SEPTEMBER 6TH, ^945 THE KEY TO THE PROBLEM : This pictorial diagram shows the difference in the areas covered by transm ssion froma tower on the ground and from an aircraft flying at 30,000ft. The transmitter power required is greatly reduced. Iralo vision artin Plans for Covering the Entire United States with Television TAST v^eejc_we-p«rBl!shed a picture of an American scheme I for using aircraft as carriers of television transmitters ••—' so as to cover a very wide area. The scheme, which owes its origin to a young engineer of the Westinghouse Electric Corporation, Mr. C. E. Nobles, and which has since been developed jointly by Westinghouse and the Glenn Martin Company, is based upon the fact that television waves travel in a straight line and, for all prac- tical purposes, stop at the horizon so that the range of a television transmitter is virtually the line-6f-sight distance to the horizon. The Westinghouse-Martin scheme proposes that a chain of aircraft should be kept flying constantly throughout the 24 hours, the origins of television and radio programmes being logically New York and Hollywood, from which the programmes would issue and be transmitted to receivers on the aircraft, which would also carry transmitters for re- transmission to the next aircraft in the chain and to receiv- ing stations on the ground within their range. Mr. Nobles explained that the average service radius of a high-powered television station is about 50 miles and that it is difficult to cover even this radius satisfactorily, particularly in the case of the high frequencies used in high- definition colour television. At present, colour television transmitters of about five kilowatts can be built, but to cover a range of 50 miles would require some 50 kilowatts. Thus a chain of transmitters across the United States would require many relay stations, each of which would introduce •a certain amount of distortion, so that by the time the picture was received at the other side of the continent the quality might well be very poor. By raising the transmitter's aerial to a height of 30,000ft. in an aircraft, the coverage range would be increased to 2ii miles, and at 50,000ft. the radius would be about 300 miles. Another interesting fact is that with high-altitude operation the transmitter power necessary to deliver a usable signal to the line-of-sight distance is sharply reduced. The 50 kW. power to 50 miles has been mentioned. One kilowatt of power will deliver from 30,000ft. the sanie usable signal at approximately 200 miles.' Many advantages follow from this. The area covered is very large, and the low-powered transmitters can be made in sizes and weights which can readily be carried in aircraft. Power of the or of one kilowatt can be generated with valves now availab- j even for C.B.S. high-definition colour television fie quencies. The small amount of power required to operate the transmitters can be obtained either from the main air- craft engines or from generator sets carried on board. Chain Across trie Continent For broadcasting and/or television the range--from air- craft to aircraft at 30,000ft. is about 400 miles, so that for relay purposes the machines would need' to be flying approximately 400 miles apart. After preliminary talks with the Martin engineers it was decided "that each air- craft should carry four television transmitters, five FM transmitters, monitoring equipment, and sufficient relaying equipment to carry four television programmes and five FM programmes. And now we will quote Mr. William K. Ebel, vice- president in charge of engineering at the Glenn Martin Company. He said: '' The • first and obvious question in contemplating anoperation covering 24 hours a day every day in the year is—
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
