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Pioneering in Electronics

Chapter Three - Television: Onward and Upward with the Art

The television viewer relaxing today in front of his bright 21-inch screen may find it hard to understand the excitement that occurred one afternoon in 1931 at the RCA, Victor plant in Camden. Merrill Trainer, a young engineer in the new television studio development group, was posing obligingly under a bank of bright lights before a cumbersome television pickup system. His image, translated mechanically into electrical signals, appeared mistily on the 9-inch screen of an experimental receiver some four miles away. Up to this point, the procedure followed the pattern established in previous tests—the appearance of Trainer’s smiling features in a close-up on the screen, and the careful adjustment of controls to bring them into approximate focus. But this time there was a significant change, one that aroused pride and jubilation among the viewers—including Vladimir Zworykin.

“We had been striving for the best picture resolution possible,” said Zworykin later. “That day, we knew we had achieved the best yet. For the first time, we saw the separations between Trainer’s teeth!” (p. 47)

The episode, of minor historical importance in itself, is a good indicator of the distance that was to be covered during the 1930s by perhaps the most intensive and systematic research and development program in the annals of communication. The result of this program was a practical commercial television system, resting upon a solid foundation of research and incorporating many remarkable scientific and engineering advances.

The accomplishment of television cannot be attributed to any individual, or even to any single group or organization. Bookshelves abound with histories of the art, beginning with Nipkow’s mechanical scanning disk of 1884, Subsequent contributions to the system have come from many scientists and inventors the world over. In many aspects of the complex art, considerable uncertainty exists as to who invented what, and when,

Two things are certain, however: Vladimir Zworykin invented the Iconoscope, the first electronic “eye” of television, and the vision and persistence of David Sarnoff are responsible for the fact that television was commercially developed and ready for nationwide service with the return of peace at the end of World War II.

Taking these as the starting point, the story is one of a man and an opportunity coming together in the right place and at the right time. Mr. Sarnoff, whose prescience in the matter of the “radio music box” had been vindicated in the phenomenal growth of the broadcasting industry, was just as confident of the bright outlook for television. As early as 1923, he was referring en­thusiastically to a future in which people at home might “see as well as hear what is going on at the broadcast station.” (p. 48)

The opportunity presented itself in two installments, beginning with the ingenuity and optimism of Zworykin. The Russian-born inventor, who had been experimenting with television at Westinghouse in the late 1920’s, painted a glowing picture for Mr. Sarnoff of the possibilities inherent in an electronic television system employing the Iconoscope as its “eye.” The RCA executive, already convinced of the inevitability and desirability of television, logically wondered what Zworykin thought the development might require in facilities and funds. Zworykin, thinking in terms of a working laboratory system, estimated optimistically that it might be handled with “a couple of rooms and half a dozen men,” at a cost of about $100,000. Quite possibly a limited system might have been achieved for this amount. What actually happened, however, was a full-blown system development program that ultimately exceeded Zworykin’s figure by some $49,900,000. Apart from the estimate, however, he did provide Mr. Sarnoff with firm evidence that all-electronic television could be achieved by someone sufficiently determined to support its development.

The second installment of the opportunity arrived with the acquisition by RCA of its own manufacturing facilities and the organization of a competent and versatile staff of scientists and engineers with experience in a substantial part of the television work that had been done prior to 1930. Besides Zworykin and his colleagues, the staff included several engineers who had been associated with Alexanderson in experimental television projects, (p. 49) as well as the RCA group from Van Cortlandt Park, Now, for the first time, these talents were Joined in one organization and turned loose with a mandate to develop a practical television system.

At the beginning, two basically different approaches were to be found within the group. Zworykin and his colleagues, working with the Iconoscope, had aspired to a completely electronic system of pickup and reception. The Alexanderson group and the Van Cortlandt Park team had based their approach upon a mechanical system, employing a rotating disc to breakdown the televised image into an appropriate high-speed scanning sequence. The initial effort at Camden succeeded in wedding the two ideas.

The result was a hybrid, described later by Charles B. Jolliffe, Vice-President and Technical Director of RCA, as “a system which brought mechanical scanning to what was believed to be the highest level then obtainable in any system.”

At the transmitting end was a mechanical scanning system developed under the direction of Ray D. Kell, a former associate of Alexanderson. This was coupled with the first transmitter to produce a 1-kilowatt output in the 45–55 megacycle range. The receiving equipment, assembled under Zworykin’s supervision, was fully electronic, employing a cathode-ray tube nine inches in diameter upon which was displayed a picture measuring 5½ by 6½ inches for reflection from a mirror in the raised lid of the receiver cabinet. Initially, the picture itself was an 80-line image, as contrasted to the 525-line picture of today’s standard television. (p. 50)

With this rudimentary system, the Camden group picked up outdoor and studio subjects at random for initial tests. While the results were far short of present-day standards, they looked promising enough to warrant more extensive tests. Accordingly, the transmitter and the studio equipment were transplanted to the upper reaches of the Empire State Building in New York and rigged for experimental broadcasting in the New York metropolitan area. At the same time, the system was altered to handle a 120-line picture.

During the latter part of 1931 and early 1932, extensive data were accumulated on such aspects as the propagation characteristics of the signals, the nature of electrical “noise” disturbances affecting reception, and the limitations of the equipment itself. The engineering conclusions boiled down to the fact that the mech­anical scanning equipment was too limited in flexibility and failed to produce adequate signal amplitude for practical television service. Furthermore, it was apparent that 120 lines were not enough for satisfactory reproduction of images.

This is how matters stood when a basically important change occurred. With the separation from the parent companies in 1932, Engstrom assumed immediate supervision of the television project. He brought to the assignment a new comprehensive approach bearing all the earmarks of the procedure that has since acquired the name of systems engineering.

In a later discussion of the project, Engstrom pointed out that the television work prior to 1932 had been conducted largely on a piecemeal basis. (p. 51)

“None of the engineering groups working earlier on television had gone deeply into the basic systems problem involved,” he said. “After assembly of the various groups at Camden, it became apparent that the electronic, rather than the mechanical, approach would prevail. At the same time, the decision was made to pull all of our television work together in the service sense. We set out to get a better understanding of what it took to achieve television standards of high enough quality for regular broadcast service to the public. This made it possible for us to set our sights higher than they had been set. We knew now that we had to put a system together, test it as a system, then go back over the components to improve the system and test it again.”

Once the limitations of the mechanical system had become apparent, the next major forward step was the development at Camden of a new type of transmitter geared to an electronic pickup system employing the Iconoscope. The equipment was set to operate at 240 lines—the maximum that could be handled satisfactorily at this stage of development.

But before the new arrangement could be adequately tested, another aspect of the system needed attention. This was the relaying technique by which the television signals might be carried over a distance for potential network service. To find the answer, the project turned to the specialists of RCA Communications, who had acquired a wealth of knowledge and experience in their work at Rocky Point and Riverhead.

The communications group had put considerable effort during the later 1920s into an investigation of frequencies above 30 (p. 52) megacycles to determine their value in long-distance communication. (This portion of the radio spectrum is known today as the very-high-frequency {VHF} range, but it was considered at the time as ultra-high-frequency {UHF}, a designation used today for a considerably higher range.) Beverage, Hansell, Peterson and their colleagues had run a long series of tests at these higher frequencies, experimenting with receivers aboard ships, planes, and automobiles ranging over the map from Maryland to Montreal and from New York to Puerto Rico.

Among other conclusions, they had determined that circuits of commercial quality were practicable at such frequencies if one or both of the terminals were placed at sufficiently high altitudes to intercept the line-of-sight transmission. At these frequencies radio waves tend to follow a straight course that carries them out into space, with the result that their intensity dwindles rapidly at ground level beyond the horizon. For this reason, the waves must be intercepted at or near the horizon and directed toward the next receiving point.

Just at the time this conclusion was reached, the Mutual Telephone Company of Honolulu, Hawaii, expressed its desire for a practical solution to the problem of maintaining reliable radio-telephone communication among the islands of the Hawaiian chain. Working independently, Mutual had ruled out lower frequency operations in the 1500–5000 kilocycle range, but had detected some promise in higher frequencies around 60 megacycles. At this point, the cooperation of RCA was sought. (p. 53)

Using knowledge acquired in their exploration of the higher frequencies, the communications engineers at Rocky Point and Riverhead rapidly developed suitable equipment and sent it to Honolulu, escorted by W. I. Matthews and S. H. Fifield, of the communications engineering staff. The transmitters, designed at Rocky Point, were capable of 75 watts output at frequencies of 37 to 60 megacycles. The equipment turned out to be just right for the job, demonstrating “remarkable freedom from atmospherics and selective fading,” according to a report by Beverage, Hansell and Peterson. On the strength of the performance a complete telephone network linking the islands was constructed for regular service in 1931. Entering commercial service in that year, it became the first practical very-high-frequency (then UHF) communication system in regular use.

What did this have to do with television? According to Engstrom, the Hawaiian system ‘‘put to test certain things on which we had to have information in the television area.” The “certain things” refer particularly to the fundamental know-how of very-high-frequency operation. Television, too, was operating in the same general frequency range as the Hawaiian system.

Out of this background, the television group undertook in early 1932 to establish a relay link that would carry broadcast signals from the Empire State Building in New York to receivers in Camden, 86 airline miles away. Possible locations for an experimental relay station were scouted by RCA and the National Broadcasting Company together with General Electric and Westinghouse, from whom the corporate separation was yet to take place. (p. 54)

The choice was narrowed down to an otherwise undistinguished knoll rising 230 feet above sea level just east of Mount Holly, New Jersey—63 miles from the towering Empire State antennas, and 23 miles from the Camden plant. At one point in the proceedings, it became necessary to make measurements at the site to determine the strength of the signal received from New York. The figures were gathered ingeniously by Charles J. Young, of the Camden staff. He hired an autogiro—an ancestor of the helicopter—and traveled up and down in pogo-stick fashion over the knoll with a receiver tuned to the Empire State transmission.

The wooded sand hill, known locally as Mount Arney, was soon festooned with gear including a 165–foot tower, a small steel build­ing that housed receiving and transmitting apparatus, and three wooden poles supporting a directional antenna aimed at Camden. Among the major contributions to the cooperative project were a series of field strength measurements carried out by Bertram Trevor, of the communications group, and a radiating antenna specially designed for the operation by P[hilip]. S. Carter.

Operating at 80 megacycles, this pioneer television relay system went into test operation in 1933 in conjunction with the 120-line mechanical-scanning system. Watching the results, Young reported jubilantly that “when the studio program originating in New York City was finally seen on the kinescope (i.e., picture tube) in the suburbs of Camden, it has passed on the way, without appreciable distortion, through three transmitters and three receivers.” Satisfactory as it was, however, the system was to last for little more than a year before the advent of electronic methods of television pickup would call for higher relaying frequencies. (p. 55)

At this stage of the television project, pictures were being transmitted at the rate of 24 frames per second—as opposed to the present-day standard of 30 frames. Combined with the 120-line and 240-line pictures displayed in these early days of the project, the result was an annoying amount of flicker in the eyes of the viewer. This was, in fact, a principal criticism in 1933, at a demonstration of the 120-line system for RCA licensees. Kell reported later that the flicker probably was more annoying to the guests than to the RCA engineering staff “because we had calluses on our eyeballs by then.”

The problem was solved by an ingenious odd-line technique of interlaced scanning, developed by Randall C. Ballard. In interlaced scanning, the electron beam in the kinescope first scans alternate lines covering the entire area of the picture on the tube face, then returns and scans the omitted lines. The effect of interlacing is to produce far greater visual continuity on the viewing screen since, in a sense, it doubles the frame rate as far as the eye is concerned.

Coincidentally with this major development, the decision was reached to advance the system to a 343-line picture with a frame rate of 30 per second, in order to obtain more image detail. With interlaced scanning, this amounted to scanning of the picture area in alternate lines 6O times each second—the standard employed in present-day television. In this context, the conception of interlaced scanning represented a major forward step in development of modern broadcast television. As Engstrom pointed out (p. 56) following the next series of field tests in 1934, “the effectiveness of interlacing as a solution to the problem of flicker was conclusively demonstrated.”

By early 1934, all elements of the complete system were receiving attention. At Camden, R. S. Holmes, W. A. Tolson and a group of associates were heavily engaged in propagation studies of the very-high-frequency television signals and in research aimed at simplifying receiver circuits. The problem of kinescope brightness and contrast was being tackled by another group including I. G. Maloff, David W. Epstein, and K[arl]. R. Wendt. Under Zworykin, Harley lams, Leslie E. Flory, and others were attempting to increase the sensitivity of the Iconoscope.

By now, too, the last mechanical element in the system had disappeared. In the 1933 system, employing the Iconoscope for pickup and the kinescope for display, the only mechanical device was a synchronizing generator. The increase in scanning lines and the growing need for extreme accuracy in signal transmission led to the development in Kell’s transmitter group of an electronic synchronizing generator to replace the mechanical unit. From 1934 on, television was fully electronic.

From Laboratory to Public Service

The RCA television project had thus achieved by the end of 1934 a system that was in all basic respects the complete black-and-white television system of today. There was obvious need for further technical refinement and improved quality, but the principal (p. 57) question now became one of public acceptance. The only foolproof means for determining whether a product or service will meet the test of public acceptance is to try it out under conditions comparable to those it will encounter in public service—and this is the decision that was now taken by David Sarnoff and the Directors of RCA.

On May 7, 1935, Mr. Sarnoff made the following statement to RCA’s stockholders:

In the sense that the laboratory has supplied us with the basic means of lifting the curtain of space from scenes and activities at a distance, it may be said that television is here. But as a system of sight transmission and reception, comparable in coverage and service to the present nation­wide system of sound broadcasting, television is not here, nor around the corner. The all-important step that must now be taken is to bring the research results of the scientists out of the laboratory and into the field.

On this basis, he announced, RCA would undertake a three-point plan of field demonstrations, involving these steps:

1.  Establish the first modern television transmitting station in the United States, incorporating the highest standards of the art. This station to be located in a suitable center of population, with due thought to its proximity to RCA’s research laboratories, manufacturing facilities, and its broadcasting center in Radio City, New York.

2.  Manufacture a limited number of television receiving sets. These to be placed at strategic points of observation in order that the RCA television system may be tested, modified and improved under actual service conditions.

3. Develop an experimental program service with the necessary studio technique to determine the most acceptable form of television programs.

From the technical standpoint, the new course charted by the RCA management meant little change in the nature of the job already being done by the research and engineering staffs. It did, however, (p. 58) signify the, firm commitment of all available RCA resources to the task of creating a practical commercial service as rapidly as possible. To this end, extensive field tests would be carried out at the same time that research was directed toward better materials, devices and techniques. Thus the groundwork was laid for an effective feedback system: while the laboratories produced new or improved elements for the system, the operation of the system disclosed needs for further research in specific areas. Applied first on a large scale in the television project, this amalgamation of basic and applied research with engineering development was employed subsequently with outstanding success in other technical fields.

As Mr. Sarnoff pointed out to the stockholders, television is a highly complicated system with thousands of interlocking parts that must be perfectly synchronized so that “transmitter and receiver will fit as lock and key.” To create and test such a system through simultaneous activities in research, advanced development, engineering and field testing, it was just as necessary that the various RCA subsidiaries function together as effectively as “lock and key.” To assure such coordination, the RCA President appointed a committee comprising the principal technical leaders of the RCA Manufacturing Company, NBC, and RCA Communications.

Advised by the various research and engineering staffs engaged in the television project under Engstrom, the committee worked out a plan that included establishment of new studios at Radio City, installation of a transmitter at the Empire State Building, a radio (p. 59) relay or coaxial cable link between New York and Philadelphia, and production of a quantity of television receivers of three different types to be installed for test viewing in the homes of RCA engineers and executives throughout the New York area.

Approved by Mr. Sarnoff and his management associates, the plan formed the basis for a field test program that commenced in mid-1936 and continued through 1938 at a cost of more than $1,400,000, exclusive of research and development expenses. A substantial part of the total went for the outfitting of studios at Radio City, installation costs of equipment and test receivers, and the many services connected with maintaining and operating the extensive facilities, The costs also embraced scores of minor items. A typical example was the $150 monthly rental of a 14th floor apartment at 95th Street and West End Avenue in New York City for the prolonged testing of receivers under home conditions.

The tests began in June 1936, on operating standards in keeping with the current stage of development. These included a 343-line picture transmitted at a frame rate of 30 per second with interlaced scanning. Transmitters in the Empire State Building transmitted the picture carrier at 49.75 megacycles, and the sound carrier at 52 megacycles, with the complete signal occupying a bandwidth of 4 megacycles, About 100 receivers with 9-inch kinescopes were produced and planted in the homes of RCA personnel throughout the metropolitan area. With them went detailed forms to be filled out by each viewer, relating to the quality of picture and sound reception, characteristics of the picture, and the performance of the receiver. Provision also was made for motion (p. 60) picture as well as live programming, in order to test fully all entertainment aspects of the system.

The broad advance from this developmental program to present-day television, operating over a range of VHF and UHF up to 900 megacycles with a 525-line picture standard, involved a series of engineering achievements and successive field tests whose complete details are beyond the scope of this story. The general outline of progress can be traced, however, through several of the major research results. Many of these evolved through the successive tests from 1933 up to and even beyond the introduction of the first public television broadcasting service in the spring of 1939. All were facilitated both by whole-hearted management support of the research effort and by the availability of a complete working system in which new theories, materials and equipment could be put to immediate test.

Pickup, Transmission, Display

A major research problem, echoing like the chorus of a Greek drama through the television project of the 1930s, was that of improving sensitivity in the Iconoscope, the all-important electronic “eye” of the early television systems. This was a problem that occupied some of the best talents in television research through a large part pf the decade.

The uconoscope was a highly satisfactory pickup tube, even by many of today’s standards, But it was a delicate and somewhat temperamental device. Basically, the tube contained two principal working parts. (p. 61)

The first was a 4-by-5-inch plate holding millions of tiny photoelectric cells. The image picked up by the camera was focused through a lens onto the plate, as in an ordinary film camera. Each of the tiny cells generated a voltage proportional to the amount of light falling upon it, creating an over-all pattern of voltage corresponding to the image received through the lens.

The second critical part was a narrow beam of electrons shot at high velocity from an electron gun within the tube. The beam was swept back and forth in successive lines from top to bottom of the plate in the standard television scanning pattern. As it passed across the plate, the beam collected the voltage from the tiny cells, causing the voltage to be conducted out through ampli­fiers. The amplifiers conveyed the information in the form of stronger signals to the transmitter.

In the process, several irritating characteristics were likely to crop up. Among them were a lack of uniformity over the mosaic of photoelectric cells, trailing or reflections in the transmitted image, and the appearance of a dark spot in the picture. These drawbacks appeared to result largely from the use of a high-velocity electron scanning beam, which struck the mosaic with sufficient force to release large numbers of secondary electrons. The emitted electrons, raining back onto the mosaic in a random fashion, tended to cause the dark spot signal.

These deficiencies were tackled by a substantial group of research specialists including George Morton, Leslie Flory, and Arthur Vance at Camden, and Harley lams, Albert Rose, and Henry DeVore at Harrison. A succession of major improvements resulted (p. 62) from this combination of talents. The photosensitivity and operation of the mosaic were improved; techniques of secondary-emission multiplication were developed to amplify the signal; various methods of image intensification were devised. The effort culminated in the achievement of a new pickup tube—the Orthicon—whose details were revealed in a technical paper by Rose and lams in 1939.

The Orthicon represented practical application of a theory that had been discussed widely in previous years. This was the use of a low-velocity scanning beam in order to avoid knocking great quantities of secondary electrons out of the mosaic target. Achieved in the Orthicon, this technique provided a far more efficient tube for many television uses. As Rose and lams pointed out, only about one-quarter of the stored charge in the mosaic of the Iconoscope was effective in producing the picture signal. In the Orthicon, they reported, “within the accuracy of measure­ment, all the photoemission is converted into video signals.”

The Orthicon was a radical forward step in one of television’s most critical functions—the initial pickup. But history was unkind. The tube appeared in commercial form just as the development of broadcast television ground to a halt before the military demands of World War II. By the time peace returned, the Orthicon had been superseded by an even more effective pickup device—the Image Orthicon, whose story belongs to the later account of wartime and postwar television progress. (p. 63)

Other RCA scientists and engineers labored mightily through this same era to create and improve a series of effective links through the rest of the system. In many cases, there was a need to explore untrodden territory as well as to improve more familiar devices and techniques. There was no precedent, for example, for transmitter tubes that could handle the full range of frequencies to which we have become accustomed today.

Surveying the status of the television project in the fall of 1935, Engstrom observed that contemporary transmitter tubes permitted service up to about 56 megacycles, far enough to accommodate only the two lowest channels likely to be assigned for television broadcasting.

“It is therefore imperative,” he wrote, “that we continue our transmitter development work and that the tube engineers and manufacturers definitely and actively go ahead with tube developments. We need tubes of outputs greater than those now available, for use at frequencies well above the point where present tubes fail.”

This amounted to a call for something new in tube design. Since higher frequencies call for smaller tubes, the tubes would have to be kept down in size. Since higher output can be achieved only with more power, the tubes would have to be capable of dissipating the larger amount of heat associated with greater power. Under the circumstances, new principles of thermodynamics and of electronics were needed. (p. 64)

Initially, the burden of this development fell upon a small group at Harrison, including Andrew V. Haeff and Leon S. Nergaard. By mid-1936, this team had developed a screen-grid tube with a peak output of 20 kilowatts up to 120 megacycles and had simultaneously contributed a useful store of new knowledge to the electron tube art. By this time, too, reinforcements had arrived on the scene with the assignment of a small group under Zworykin’s direction. Among the arrivals were Malter and L. P. Garner, and, a few months later, Philip T. Smith. By 1939, the combined efforts of both groups had resulted in tubes producing 50 kilowatts over a range of frequencies from 40 to 108 megacycles.

Thus, transmitter tube development up to World War II advanced to the point of handling the first five channels on the selector dial of the television receiver. But the means still did not exist for transmitting with useful power (5 kilowatts or more) at the frequencies beyond Channel 5. The project happened to fit into the pattern of urgent wartime need for improvements in radio communication systems. Hence the work was continued during the war, principally by Smith and Garner, who centered their efforts on a new type of tube which Smith had introduced in 1938—the so-called duplex tetrode. The result for commercial broadcasting was the transmitter tube which literally put television on the air over the entire VHF spectrum immediately after the war. This was the RCA 8D21, capable of producing 5 kilowatts at frequencies up to 300 megacycles, considerably beyond the 216-megacycle upper limit of commercial television broadcasting in the VHF band. (p. 65)

By 1938, too, the system had gained substantially from an improved technique devised by George Brown to broadcast a maximum of picture information within the 6-megacycle bandwidth that was to become standard for television transmission. The television signal, like that of radio, comprises a carrier and sidebands containing the broadcast information—in this case, the picture. Brown’s contribution was a filter which lopped off the lower sidebands, permitting a shift of the carrier to the low end of the 6-megacycle channel and the use of virtually the whole bandwidth for the upper sideband with its picture information. The result was a doubling of potential resolution in the picture at the receiver.

Outstanding basic work went also into the matter of picture display. There was, after all, little point in perspiring over the problem of pickup, transmission, and other aspects of a complex television system if the end product could not be seen by the home viewer without the risk of eyestrain. The questions here were the brightness and color of the phosphor screen in the picture tube.

In the early years of television development, picture tubes had been equipped with green-emitting screens of willemite, a material found in nature, or copper-activated zinc sulfide. These materials produced recognizable images, but they required relatively darkened surroundings, and they were apt to appeal most to the viewer with a particular liking for green. The desirable objective was the achievement of new materials that would emit white light of sufficient brightness for home viewing in normally (p. 66) lighted surroundings. This was a job for chemistry—specifically for Leverenz and his associates.

The physical phenomenon involved in the case of television phosphors is cathodoluminescence, the property of emitting light under bombardment by electrons from a cathode. As Leverenz recalled later, the development of better phosphors called for “the creation of new materials made by chemical means, but whose performance was based on physics—a matter of using chemistry to achieve certain physical conditions.”

The scale of the phosphor research program, and an important discovery that came about in the course of the work, were indicated by Leverenz in a report published in 1938:

It is significant to note that cathodoluminescence should probably be classified as a general property of solid matter—not just a phenomenon observed in isolated cases. Over 6,000 widely different solid substances and materials, both vitreous and crystalline, having widely varied degrees of purity or impurity, have been synthesized and tested in our laboratories. Every one of these materials showed discernible luminescence under electron bombardment.

Unprecedented precision also was required in synthesizing these materials. Leverenz noted that the addition or subtraction of as little as .0001 per cent—one part in a million—of a foreign substance could alter the properties of some of the phosphors by as much as 50 to 100 per cent. This degree of purity, now a familiar and essential feature of solid-state electronics, had been virtually unheard of prior to the phosphor research effort in the 1930’s. (p. 67)

The principal result of these exhaustive studies was a gradual evolution from green to yellow to sepia to white as more efficient phosphors were produced. With the change came steady improvement in television viewing, keeping pace with the other improvements in the system.

There was also an unexpected and important by-product from the phosphor program. The most satisfactory material produced by Leverenz and his group was a fluorescent compound of zinc beryllium silicate, capable of emitting a range of colors with wholly unprecedented efficiency. As Leverenz noted subsequently, light efficiency customarily had been measured in terms of watts per candle, while the new material produced results that could be measured in terms of candles per watt—“a good deal like the difference between gallons per mile and miles per gallon.”

These results awakened lively interest as a potentially important new source of light for general illumination. Made available by RCA, the material was promptly put to use in the first practical fluorescent lamp, whose efficiency marked the start of a new era in space lighting. Employed for several years as the light-emitting surface inside the fluorescent lamp tube, the RCA zinc-beryllium-silicate compound eventually gave way to other materials with more desirable characteristics for this particular application. (p. 68)

Antennas and Relays

Two of the most bizarre props ever employed in research were reared on the RCA premises at Camden and Rocky Point during the television project of the 1930’s. These were replicas of the summits of New York’s tallest structures—the Empire State and Chrysler buildings. The buildings themselves were admirably suited to television broadcasting requirements from the standpoint of altitude. From their lofty peaks, transmitting antennas could radiate signals over ranges of sixty miles or more by direct line of sight, eliminating the need for specially constructed towers. In developing the most effective antennas, however, it was necessary to create and test various designs under conditions approximating those of actual service. To RCA’s antenna experts, it seemed more practical to recreate the tops of the two buildings at ground level than to clamber around the upper reaches of the structures themselves, exposed to wind, weather, and other high altitude hazards.

This aspect of television research produced a series of extremely useful results and established the pattern for all subsequent transmitting antenna design. Perhaps the most successful product in this phase of the program was the turnstile antenna developed by George Brown and his associates in General Research at Camden. The turnstile derives its name from its appearance:  its crossed dipoles, extending outward at 90-degree intervals from a vertical shaft, resemble the turnstile familiar to subway riders. (p. 69)

The development of the turnstile was sparked by a request to Brown for a new type of antenna useful for facsimile transmission, under study by RCA in the mid-1930s, To Brown, the most desirable technique appeared to be one that wouJd “pancake” the wave propagation pattern, concentrating the energy in a vertical plane and distributing it horizontally in all directions. The solution came to him at two o’clock one morning, when he arose from bed to write down his thoughts. With the help of Jess Epstein, a colleague on the Camden staff, the conclusions were translated shortly into an experimental antenna, fashioned from a steel pipe flagpole rising above a test shack at Camden.

After a series of successful tests, the first operating turn­stile antenna was installed with a transmitter at the Columbia-Presbyterian Medical Center in uptown New York for experimental facsimile operations. This pioneer model consisted of six crossed dipole assemblies in a series of layers on the vertical shaft, providing a gain of four times in transmitted power. Its operation revealed a further virtue of the design—an inherent broad band characteristic, from 5 to 6 megacycles in width. During 1937–38, measurements were made with television signals received from the Empire State Building to determine whether the turnstile could perform as effectively for television as it performed for facsimile. It could, and did—although widespread application of the design awaited the swift growth of commercial television after the war. (p. 70)

A number of turnstiles were put into operation during the latter 1930s for FM radio transmission, including an installation at the top of Mount Washington in New Hampshire, where automobile springs were used as turnstiles in order to withstand the heavy ice formations occurring in winter. The Chrysler Building entered the picture in 1937 as the proposed site of a transmitting antenna for the Columbia Broadcasting System. In order to test the most effective design, Brown and his colleagues made use of a full scale model of the building’s peak, constructed of heavy timbers and measuring 80 feet wide and 135 feet high. The structure was placed in an open area opposite Building 53 in Camden and used for several months as a highly successful test bed for various dipole arrangements. When the project was completed, Brown avoided the cost of dismantling the structure by calling in a truck to pull it over, and passing around word that free lumber was available for the taking.

The Camden group completed in early 1940 the first turnstile antenna specifically built for television transmission. Tested in the system shortly before the war, this became the prototype for the transmitting antenna installed on the Empire State Building in 1947 for commercial broadcasting.

Further contributions of importance to antenna development came during this period from the group at Rocky Point, including Lindenblad, Peterson, Carter, and others. Drawing upon basic knowledge accumulated through the 1920s and early 1930s, the Rocky Point team created a series of successful antennas for use (p. 71) during the system development program after 1931. Since these were designed principally for use on the Empire State Building, a scale model of the building’s summit was erected at the Rocky Point site and employed to simulate the environment in which the antennas were to be placed, The initial Empire State antenna, used from 1931 to 1936, comprised a set of two separate vertical dipoles for the audio and video signals. With the step upward to 343 lines in 1936, a new arrangement was required to handle the greater bandwidth. Working with the mockup of the building, Lindenblad devised a new triangular array of horizontal dipoles, which did the trick until the decision was made to move up again to 441 lines in 1938.

To meet the new requirements of wider band and higher frequencies, Lindenblad designed the broadest band antenna that has ever been built for television. This was a modified turnstile type, based on the principles conceived by Brown, With its four radiating arms resembling a quartet of elongated footballs, the new antenna became a New York landmark after its installation in 1938, standing as a symbol of the new television art until its replacement in 1947 by the improved but less picturesque turnstile antenna.

These antenna developments solved the problem of radiating signals most effectively from a single broadcasting station. There remained the matter of relaying to distant points in order to provide network service. In developing suitable relay systems, a large share of the load was carried by the communications group under Beverage, with notable help from the research staffs at Harrison and Camden. (p. 72)

When the pioneer relay link at Mount Arney entered experimental use in 1933, there was general recognition that relaying soon would have to cope with far higher frequencies than the 80 megacycles employed in the initial system. It was equally apparent that effective network relay service would require a series of such links, operating through unattended automatic relay stations.

Shortly after the Mount Arney installation was completed, the communications group had developed an unattended automatic radio-relay system for teleprinter and facsimile communication between New York and Philadelphia. Two repeaters were used, one for south­bound and the other for northbound traffic, with relay points at Mount Arney and at the RCA Communications transoceanic station at New Brunswick, New Jersey.

Handling frequencies of about 100 megacycles, the system entered commercial service in 1936 and provided nearly five years of continuous unattended operation until it was closed down by government order at the beginning of the war. According to Hansell, the system “provided a service of greater reliability than had been obtained with cable pairs over the same circuit, and proved that radio relaying with fully automatic, unattended repeaters is practical.”

This was valuable experience, but it left unsettled the matter of very-high-frequency operations over the spectrum into which television was spreading. To achieve the desired frequencies, something new was needed in the way of high-frequency amplifying tubes. The answer was found in Harrison, where Haeff and Nergaard (p. 73) were developing something new and different. This was a tube known as the inductive output tube, a forerunner of the klystron power tube that was later to come into wide use as a generator of centimeter waves for radar.

The inductive output tube employed entirely new principles. For example, the electrons did not strike the output electrode as in a conventional tube, but gave up their energy instead by electrostatic induction before being collected by another electrode at a constant potential. By 1939, an inductive output tube had been produced which was capable of 30 watts of output at 500 megacycles—a level which was immediately useful over all television frequencies.

Armed with the new tube, the communications group rushed to completion in 1939 an experimental relay system linking the Empire State Building and a terminal receiver at Riverhead through a relay station at Hauppage, in the center of Long Island. Broadcast from the Empire State at 45.25 megacycles, the signal was converted at the Hauppage automatic relay station to 500 megacycles for transmission to Riverhead, where it was reconverted to the lower broad­cast frequency. It was in connection with this system, incidentally, that Lindenblad developed the concept that brought him the first patent on the traveling-wave tube, a device that was to undergo considerable further development in the postwar years for widespread application as a low-noise amplifier at microwave frequencies.

In 1940, another unattended relay point was established at Bellmore, Long Island, and another terminal receiver at the RCA Building in New York. These additions permitted the relaying of (p. 74) programs around the circuit via Hauppage and back to New York for a series of historic demonstrations during 1940 and 1941 to RCA licensees, the industry’s National Television System Committee, the Federal Communications Commission, and the public.

These demonstrations, coming just before the wartime postponement of commercial television development, were proof that the most difficult pioneering work had been completed, laying a firm technical base for the post-war extension of television network service across the nation by means of an ultra-high-frequency radio relay system.

Frequency Modulation

It is worth noting that this first successful UHF relay system for television employed frequency modulation (FM) techniques developed over more than a decade by the communications group for specific application in high-frequency point-to-point communication.

In frequency modulation, the power of transmitted radio waves remains constant while the frequency varies in accordance with variations in the input signal. This is the opposite of amplitude modulation (AM), in which the frequency remains constant while the power varies in accordance with variations in the input. AM is the technique employed in standard radio broadcasting.

Under the direction of Peterson at the Riverhead laboratory, Murray Crosby had made important contributions in the early 1930s to the theory and practical application of frequency modulation.  His theoretical studies and experimental confirmations are, in (p. 75) fact, still considered as a “bible” by many engineers working with frequency and phase modulation. As developed for point-to-point service by the RCA communications research group, FM was employed first in narrow band transmission and reception. With the advent of ever-higher radio frequencies and higher frequency services, however, the application of a wide-band FM technique for radio broadcasting became feasible. A proposal for such a system came in the mid-1930s from Edwin H. Armstrong, pioneering radio engineer, one of whose most notable contributions to radio was the super­heterodyne principle.

The use of wide-band FM in sound broadcasting appeared to offer important advantages, such as the reduction of high-frequency hiss in receivers. To obtain these benefits, however, a far wider band of frequencies was required than that used in AM broadcasting. The Armstrong proposal called for an FM bandwidth of 200 kilocycles, as compared with a standard bandwidth of 10 kilocycles for AM broadcasts. As the radio spectrum was extended upward into the VHF and UHF ranges, however, sufficient room was becoming available for the proposed FM service. At the same time, the use of the higher frequencies offered the further inherent advantage of relative freedom from natural static.

In the development and testing of the television system, the RCA research and engineering groups had installed in the Empire State Building an array of transmitting facilities suitable not only for television but also for experimental high-frequency FM use. During 1934 and 1935, the RCA group cooperated with Armstrong (p. 76)

in conducting a series of extensive field tests of the proposed FM system under practical operating conditions, employing the Empire State Building transmitter. In addition, results of earlier FM studies by the communications group were made available.

The practical results accumulated in the field tests contributed substantially to the launching of FM radio broadcasting service in the VHF range. By 1939, Armstrong’s first transmitting station was in operation, and within a year a dozen other stations were broadcasting. In 1940, regular FM broadcasting was initiated in New York by the National Broadcasting Company, and RCA advocated in a hearing before the FCC that FM broadcasting be authorized on a full commercial basis.

Subsequently, continued research by RCA specialists led to basic improvements in FM receiving equipment. Among these were a receiver developed by George Beers, of the Camden staff, with superior noise reducing properties and channel selectivity, and a ratio-detector FM reception circuit developed by Stuart N. Seeley, Director of the RCA Industry Service Laboratory. The Seeley circuit was a major contribution to the reduction of FM receiver cost to a level comparable to that of standard AM receivers.

Television:  Creating a Service

In a relative sense, the FM contributions remained secondary as compared with the television development program. In reviewing the outstanding research and engineering contributions to the television project through the 1930s, it has been possible to touch (p. 77) upon only a few of the basic developments that led to achievement of an effective commercial system. A full study would call for equal attention to such achievements as the basic studies by Engstrom in the early 1930s on the subject of television image characteristics, the successful work of Engstrom, Beers, and Alda V. Bedford in developing motion picture techniques and equipment for television broadcast, and the creation of large-screen systems for theater display.

The last of these items was the subject of a long-range effort over several years by a large number of specialists including Daniel O. Landis, D. W. Epstein, Maloff, [William] Tolson, [Arthur] Vance, Russell R. Law, F[rederick]. H. Nicoll, and others. Its objective was the development of projection kinescopes and lens systems for producing bright images on large screens. One result of particular interest was a novel lens system based upon the principles of the Schmidt astronomical camera, together with a high-voltage kinescope developed by Epstein and Nicoll for operation up to 50,000 volts.

These components were employed in an advanced theater projection system demonstrated publicly in May, 1941, at the New York Theatre in Manhattan, in conjunction with the new UHF relay system on Long Island. Program material was reproduced on the theater screen with a brightness comparable to that of standard motion pictures, promising the extension of television into a new service for large gatherings. (p. 78)

The technological effort that has been described here at some length was accompanied by a number of non-technical activities equally important to the successful functioning of a complete television system. There was, for example, the question of entertainment value—a subjective matter, perhaps, but one that had to be considered.

As the technical developments followed one another in rapid sequence, it was frequently difficult to review the whole system and its objectives on a broad basis. One effort to overcome this difficulty was the occasional review in Camden of feature-length movies on television as a possible means of judging the potential entertainment value of the system. According to Engstrom, this did help to determine the ability of the system “to create a satisfactory illusion,” but he also pointed out to Beal that an overall perspective was hard to achieve on a day-to-day basis, particularly “because we constantly repeat the same test material.”

As the work progressed through the 1930s, a greater variety of test material became available. At the National Broadcasting Company, the engineering department under O. B. Hanson energetically pursued the development of studio equipment and of camera and lighting techniques. Special programs became more frequent. Scores of these were arranged during the 1936–38 test period and later for professional groups, for industry representatives, for foreign visitors, for RCA licensees, and, perhaps most important, for the Federal Communications Commission. (p. 79)

Development of a new mass communication service for the public was, after all, of primary importance to the FCC as the government regulating body. By the same token, it was of paramount interest to the rest of the communications industry. These facts were taken fully into account by both management and research staffs of RCA during the development period, There was clear recognition that television would have to be more than a one-company service, once its technical and economic soundness had been established. It followed from this that broad participation would be required—first, because agreement was necessary on standards to be recommended to the FCC as a basis for commercial broadcasting, and second, because a broad base and a competitive character were essential to the healthy growth of the new industry.

Standards were required for television so that receivers could be built and sold with the assurance that they would receive programs from any one or all transmitters. Starting in 1936, committees of the Radio Manufacturers Association, including various members of the RCA technical staff, studied and initiated tests of the systems and components basic to standards of television transmission. From this work came a set of industry standards that were submitted to the FCC for study and approval.

The FCC prepared its report late in 1939 and held two public hearings in early 1940. The occasion disclosed publicly an industry pattern that was to repeat itself during the early 1950s in relation to color television—i.e., a division between the advocates of progress and the conservatives who were reluctant to (p. 80) encourage a new activity competitive with current business. On the basis of this division of opinion, the FCC at this stage authorized continuation of the “experimental” basis for the system.

The next step was formation of a new industry group, the National Television System Committee (NTSC), under sponsorship of the Radio Manufacturers Association and in cooperation with the FCC. RCA continued its full cooperation with the new industry group. Plunging into a thorough review and study of the situation, the NTSC emerged with a new set of standards, which received FCC approval in 1941. Under these standards, the system acquired the 525-line picture and other characteristics of the present commercial service. The approval came, however, just in time to encounter World War II and the diversion of the nation’s electronic resources to the war effort.

To both the management and the research staff of RCA, a milestone was passed well before the authorization of commercial standards by the FCC. The complete system, developed in nearly a decade of coordinated research and engineering, was unveiled as a public service by RCA at the New York World’s Fair on April 20, 1939. David Sarnoff, standing before the Iconoscope camera at the RCA Exhibit Building on the fair grounds, said:

The long years of patient experimenting and ingenious invention which the scientists of the RCA research laboratories have put into television development, have been crowned with success. I salute their accomplishments and those of other scientists both here and abroad whose efforts have contributed to the progress of this new art. (p. 81)

Later, summarizing the status of television in a statement to the Senate Committee on Interstate Commerce, Mr. Sarnoff recapitulated the work of a decade and emphasized the continued determination of RCA to support further research and development essential to the full growth of television as public service:

Because it recognized (television) as a fundamental development, the Radio Corporation of America has already invested more than $10 million in research, development, experimentation, patents, field tests, and actual program service. For more than ten years, five major engineering groups of the RCA organization, including its broadcasting and manufacturing, have been engaged in a coordinated attack on the problems of transmission, reception, tube development, radio relaying, and programming. . .

These expenditures are only a drop in the bucket to what will be required for further research and development in the next twenty years. Almost two decades have elapsed since the introduction of sound broadcasting on a commercial basis, but improvement still continues; and I can safely say there is little we have achieved today that will survive the next ten years.

The television research achievements of the Radio Corporation of America to date have been set forth publicly in 229 papers and reports to scientific societies, 671 additional technical reports, and two major textbooks, a total of approximately a thousand engineering studies. We believe that. . . the Radio Corporation of America has done more to develop high television standards than any other organization in the United States. (p. 82)

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