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An Introduction to Television
January 1945 Radio News

January 1945 Radio News
January 1945 Radio News Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio & Television News, published 1919 - 1959. All copyrights hereby acknowledged.

"We are standing on the threshold of the Age of Television!" "Television will enliven and broaden your life more than you can now appreciate. It will become part of your daily life just as radio is today." "The best evidence that the public thinks well of television is the universal response that comes from those who have a chance to see it." Broadcast television which will add a new dimension to home entertainment and will provide one of the most powerful mass advertising media ever developed." So proclaimed spokesmen for Dumont, Farnsworth, Philco, and General Electric, respectively, in 1945. GE clearly had its future pegged on the real revenue potential of any mass media: advertising dollars. I wrote recently of the near doubling of time allocated to each broadcast hour for commercials today compared to the in the 1960s. Companies will pay $4 million for a 30-second spot for Super Bowl XLIX this year.

An Introduction to Television

By Edward M. Noll

The first of a series of articles to be presented to the serviceman on the subject of television, covering operational principles and servicing techniques.

Method of relaying television programs from station WNBT, New York City - RF Cafe

Method of relaying television programs from station WNBT, New York City, to General Electric's station in the Helderbergs and from there to the Capital district. GE's studio, WRGB, at Schenectady, also relays programs to the main transmitter.

Are you prepared for television? Are you prepared to guide the television bandwagon when the television beam sweeps across the screens of a million television receivers? Manufacturers predict every major marketing area will be served with stations within a year after peace. Surveys of public opinion indicate extraordinary interest in television. You, Sgt. or Mr. Radioman, in the immediate postwar era, will be called upon to service, install, operate, or teach the principles of television equipment. You have been absorbing many new circuits and applications of vacuum tubes under the impetus of war - so why not, while you're in the stride, set aside a few hours each month to obtain a necessary background in a pioneer industry. What you learn about television now will not only aid you in your present activities (practically every radio concept manages to become involved in television at some point) but is an educational war bond to be cashed in at a later date.

Personnel with a working knowledge of television will be in demand. Personnel, not only to staff the production plants and the big stations but personnel to sell, adjust, and service receivers. The television receiver, in its present state, is critical of installation and adjustment. You can not throw a piece of antenna wire out the window, plug into the wall socket, turn the switch and expect to get a presentable picture. Your television receiver, no matter how well it is engineered, is useless without careful installation, a good antenna, and proper adjustment. You, Mr. Serviceman, must be able to do your part. The customer will not pay cash-over-the-counter for his receiver, pick it up and take it home. Final payment will be made when the receiver is properly installed and receiving a satisfactory picture. The television serviceman will have to bring out his glasses, light up his easy-chair pipe, and study a few hours every so often. The serviceman who knows "why" as well as "how" will be a faster trouble-shooter than the mechanical robot who knows how to handle a test panel but doesn't know what he's looking for. All of this demonstrates the need for trained personnel. Although the purpose of this series, primarily, is to present the television receiver to the serviceman, the first few installments will cover the complete system to unveil television in its entirety.

Television Stations

The four classifications of television stations are commercial, experimental, remote, and relay stations.

 - RF Cafe

The control room at WBKB. Chicago. The program director, in the foreground, masterminds the production in the adjoining studio by means of an intercommunication system connecting her directly with each of the operating personnel.

1. Commercial stations are of two types: the large regional station with its high-power and elaborate facilities, and the small local station, with its limited facilities. The local station nevertheless will have the same high-quality broadcasts, as it will re-televise the larger regional station, augmented with the local broadcasts it can readily handle with its own limited facilities. A wide variety of programs have been broadcast from the nine licensed commercial television stations shown in Table I. The Philco station in Philadelphia has been especially successful in handling sports events - particularly football. Not only is the picture clear but the operation of the system is fast enough to follow each play without difficulty. The General Electric station in Schenectady has obtained gratifying results in telecasting operas and stage plays. Its elaborate studio facilities have demonstrated what can be done in the production of first-rate stage shows. The New York stations broadcast many live talent shows - from instructions to air-raid wardens over the NBC station WNBT to the antics of a live duck over CBS station WCBW.

At present there are 70 applications pending before the FCC for commercial television stations. Many of these applications come from smaller cities. It is evident, wide television coverage is not too far off. The average cost of establishing a television station is approximately $200,000; cost, of course, is dependent on how elaborate the station is to be. The small town local with a relay connection to a larger station could begin with only a limited amount of equipment - perhaps only a small motion picture camera to handle local advertising and film broadcasts.

2. Remote stations will operate in conjunction with the commercial stations to handle the remote telecasts. The remote station generates its own signal at a very-high frequency which is picked-up at the main station and retelecast on the main transmitter. Remote telecasts have been very successful for both day and night events.

3. Relay stations permit the transfer of television programs from city to city bringing high-quality telecasts to the smaller cities and rural districts. Ordinarily, the small local station will not have the facilities to present a continuous stream of elaborate telecasts but will depend on his big city brother to give him additional talent. There are two successful relay systems on the East Coast. One is between NBC's New York station and the Philco station in Philadelphia; the other, between New York again and the General Electric station in Schenectady. The latter relay system has one jump of 129 miles which is considerably, beyond normal line-of-sight transmission.

Thus it appears that the wise use of directional antennas and proper choice of site will go a long way in extending the range of television transmission. General Electric is encouraging the use of a very low power combination local and relay station which will receive its energy on a highly directional beam from the larger station and retelecast it at a higher frequency for local coverage. The relay and local station will require a minimum of equipment and will be practically automatic in operation. Facilities will be available for handling local shows.

4. Experimental stations must be given free rein in conducting experiments which will advance the television art. All the production plants and television broadcasters are to be commended in developing cathode-ray tube television to its present state. Furthermore, under the impetus of many war disclosures, television should rise to its technical heights.

Tabulation of commercial television stations that are in operation - RF Cafe

Table I. - Tabulation of commercial television stations that are in operation.



Chart showing the possible increase in television broadcasting stations - RF Cafe

Table II. - Chart showing the possible increase in television broadcasting stations.

The Columbia Broadcasting System advocates the use of higher frequencies to obtain greater picture definition, higher frequencies also being more adaptable for color television. The development of the art must not be impeded by rash business tactics and premature technical freezing. Experimental licenses should be granted freely for development work on the very-high frequencies. The radio amateur must be given a television channel, along with the educational institution which will introduce television to the radio jobber, serviceman, or the young engineer.

Television Frequencies

One television station is six megacycles wide; the entire broadcast band, one megacycle wide. The very wide bandwidth is necessary to transmit a clear and sharp picture. In fact, a picture transmitted on a still wider channel would be further improved. The Columbia Broadcasting System is a progressive advocate of higher frequencies and broader channels, recommending 16-megacycle channels in the frequency range from 450 to 950 megacycles. At present there are 18 television channels, each 6-megacycles wide, extending from 50 to 294 megacycles. However, only the first four channels, 50 to 84 megacycles, are occupied by commercial stations.

At a recent session of the television panel of the Radio Technical Planning Board the following frequency recommendations were prepared for presentation before the Federal Communications Commission.

1. The use of 26 6-mc. commercial channels extending from 50 to 246 megacycles.

2. The use of a number of 12-mc. relay channels from 162 to 294 megacycles.

3. The use of 20 10-mc. relay channels between 300 and 1,000 megacycles.

4. The use of 20 20-mc. relay channels from 1,000 to 3,000 megacycles.

5. The use of 30 20-mc. experimental channels from 600 to 2,000 megacycles.

6. The use of additional allocations for experimental channels from 3,000 mc. to 10,000 megacycles and higher.

Television System

Each charge represents the relative brightness of one tiny spot on the picture tube - RF Cafe

Fig. 1. - Illustrating the progressive series of electrical charges during a television transmission. Each charge represents the relative brightness of one tiny spot on the picture tube. During transmission. the object being telecast is focused on the mosaic. The image appearing on the mosaic, after being scanned by a beam from the electron gun, is applied to the video amplifiers. Synchronizing and blanking pulses then combine with the picture signal and the composite video signal is applied to the transmitter and radiated by the antenna. During the receiving process the television signal is picked up by the receiving antenna and detected by the receiver. Picture signal and blanking pulses then pass through the video amplifiers to the beam-control grid of picture tube. Synchronizing pulses are applied to the synchronizing circuit to control operation of electron gun. Modulated picture beam scans the fluorescent picture-tube screen. reproducing the original image.

A televised scene is not transmitted instantaneously. It is transmitted as a progressive series of electrical charges, each charge representing the relative brightness of one tiny spot on the scene. Approximately 350,000 of these spots are required to mold one scene, and, to simulate motion in the picture, thirty complete scenes or frames are transmitted each second. As shown in Fig. 1 the object is focused through a lens system on the light sensitive screen or mosaic of the television pickup tube. The image on the mosaic, which is dotted with millions of tiny photoelectric particles, displaces electrons according to the light distribution of the image. This image is scanned by a pinpoint electron beam which races back and forth across the screen as directed by the electron gun of the pickup tube. When the beam scans one line on the mosaic a progressive series of very small charges (video signal) are released. The relative strength of each individual charge is dependent on the intensity of the light focused on the particular spot it represents on the mosaic. After one line is scanned the beam snaps back and scans another line beneath the previous one. This process continues until 525 lines are covered, representing one scene or frame. Then the beam returns to the top of the screen and scans the first line of a new scene. Point-after-point, line-after-line, and frame-after-frame, the television signal is transmitted in an endless stream from transmitter to receiver. At the receiver the same parade of charges excites the control grid of the picture tube's electron gun. The beam from the picture tube's electron gun, in step with the motion of the pickup tube beam, scans a fluorescent screen. However, instead of releasing a charge the intensity of the beam itself is changed in accordance with the variations of the received signal. Consequently, the illumination of the screen is varied point-by-point and line-by-line, reproducing the original relative light distribution of the image, on the screen of the receiver tube.

Two other types of information transmitted on the television signal are synchronization and blanking. The synchronization signals are a series of rectangular pulses which keep the scanning beam of the television picture tube in step with the scanning beam of the pickup tube. Consequently, the receiving tube beam is always directed toward the same relative spot on the fluorescent screen as the pickup beam is scanning, at the same moment, on the mosaic. The sync pulses also set the time at which both scanning beams snap back from left to right and from bottom to top. Since a definite time interval is required for the beam to snapback or retrace, a retrace line would ordinarily be visible on the screen. Another pulse, called a blanking pulse, removes this possibility by shutting off the beam from the electron gun during the retrace intervals. Next month's installment discusses in detail the scanning process and construction of the standard television signal.

Predictions of the vastness of the future television industry, brought out by some of the major television interests.

James L. Fly Former Chairman, FCC.

"Demobilization day will find television a fully explored but wholly unexploited field. We can anticipate a widespread demand for consumer goods such as television sets, many factories able and ready to convert back from war production to such consumer goods, and all the other factors necessary for the most rapid postwar period television expansion.

"I think it quite likely that during the postwar period television will be one of the first industries arising to serve as a cushion against unemployment and depression. Radio broadcasting served that function in a measure during the 1920's, though at the close of the war wireless was far less developed than television will be at the close of this war. There is no reason now apparent why we should not aim at a 50,000,000-set television industry mirroring the present 50,000,000-set broadcast industry."

Philco Corp.

"Approximately $25,000,000 has been invested in television research and development by the radio industry to get television ready for the public. Probably never before has the product of a great new industry been so completely planned and so highly developed before it was offered to the public as has television. Through long years of research and development, the television art has been so perfected that the product itself and the service it renders will be ready for the public in a highly-developed state as soon as the war is over.

"The best evidence that the public thinks well of television is the universal response that comes from those who have a chance to see it. As soon as television receivers can be made and sold, the public will eagerly buy them in tremendous quantities. It may be possible to produce and sell table model television receivers for as little as $125 after the war. Larger 'projection type' sets, giving a picture 24 inches by 18 inches may cost up to $400."

General Electric

"As we see it there will be two major applications for television after the war. The first, and perhaps the most important is broadcast television which will add a new dimension to home entertainment and will provide one of the most powerful mass advertising media ever developed. Secondly, there is industrial television in which pictures and sound will be carried by wires or by radio transmitters from one point to another for various private commercial uses. For example - industrial television might be used as a powerful merchandising medium by a department store. The fashion show taking place on the eighth floor might be wired to display projectors located on all other floors of the store and in the show windows, enabling shoppers throughout the store to see the latest styles.

"Theater television may well be of the industrial variety. A live-talent program originated at a central point could be wired to a number of theaters and then projected on the regular theater screens. News and sporting events could be made available to the audiences of a large number of theaters by such a system."

Columbia Broadcasting System

"Almost total military secrecy surrounds the surging story of electronic progress in the war. But the effect of this progress on U. S. post-war television - if the television industry will seize it - is well known to nearly every engineer who has worked, often around the clock, on the deadly electrons of war.

"Enough has already been done - developed, tested, proved, and put to work - to strike off the technical shackles that held prewar television to a relatively coarse-screen picture; enough to free television from the straitjacket of narrow-band, black-and-white transmission; enough to promise pictures twice as large and twice as rich in detail, as well as pictures in full and brilliant color. Enough, in sum, to make the 'good-enough' pictures of prewar vintage seem not good enough at all, in terms of postwar possibilities."

Farnsworth Corp.

"Television will enliven and broaden your life more than you can now appreciate. It will become part of your daily life just as radio is today."

"It will be housed in a handsome cabinet, differing from a radio cabinet only in that it brings you sight as well as sound of distant events while they are taking place! As with radio, you select and tune in the programs you want.

"Television is a new service with characteristics and powers peculiar unto itself. It combines qualities of movies, newspapers, radio, and stage. Television will bring you entertainment ... Broadway or Hollywood openings, operas, plays, movies, concerts.

"It will show news being made ... spot news of fires, parades, politics, disasters, picked up by traveling television cameras ... commentators who can illustrate maps and places and people.

"And it will bring you advertising, show you the products, how to use and care for them.

"Television will be your window opening on the world - a magic window that gives eyes to radio, and will give you a sense of personal participation in faraway events as they happen."

Dumont Laboratories

"We are standing on the threshold of the Age of Television!"

"Soon, imagination and genius, freed of wartime limitations, will be breathing vibrant life into television's magnificent promise.

"Television did not come to a technical standstill when America entered the war. When the new science of electronics was drafted for the creation of secret weapons, the technical progress of television continued in many specialized ways ... resulting in countless refinements in high-frequency circuits, in precision methods of manufacture, and many hush-hush developments of important benefit to television which may not be discussed at this time."





Posted  January 11, 2015

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