During the first half of 1932, an experimental television system had been used in New York using a studio scanning apparatus. This consisted of a mechanical disk, flying-spot type, for an image of 120 lines. Even for small areas of coverage and for 120 lines, the resulting signal amplitude was unsatisfactory. In the Camden system, an iconoscope was used as the pick-up device. The use of the iconoscope permitted transmission of greater detail, outdoor pick-up, and wider areas of coverage in the studio. Experience indicated that it provided a new degree of flexibility in pick-up performance, thereby removing one of the most technical obstacles to television.1
After many years of research and development an all-electronic television system emerged from the laboratory in 1933 for actual field tests. These tests were carried out at Camden (New Jersey), using a video transmitter and connected to it by a coaxial line. Iconoscopes (television cameras) were used to pick up scenes both in the studio and out-of-doors. A scanning pattern of 240 lines made it possible to obtain a picture with good definition, but as the frame frequency was 24 cycles, without interlacing , flicker was quite noticeable.
Dr. Vladimir Kosma Zworykin, who joined RCA in 1929 was in charge of television development as the Director of Research. He kept personal photographic records that have just been discovered and include important photographic images of previously unknown experiments.
The following year (1934) the number of lines was increased to 343, and an interlaced pattern having a field frequency of 60 cycles and a repetition rate of 30 frames per second was adopted. The results of these tests were so satisfactory that it was decided to continue them in New York City, the site of earlier RCA tests using a mechanical scanner. The advantage of the new location was that transmission studies under more nearly the conditions encountered in actual broadcasts were possible, in particular, with respect to noise and reflection from buildings. This move was made in 1935, tests followed the following year. The New York studios were located in Radio City. The transmitter was installed in one of the upper floors of the Empire State Building, with the antenna on the mooring mast, 1285 feet above street level. Two links interconnect the studio and transmitter. One of these is an underground coaxial cable approximately a mile in length. An ultra-high-frequency radio relay link operating at 177 megacycles serves as (an) alternative for interconnecting the two units. In order to increase the flexibility of the system, and to permit outdoor and indoor pickup from remote points, a mobile unit consisting of a pickup truck and transmitter, which operated at 177 megacycles, was placed in service in 1938.
1. E.W. Engstrom, "Television"; "An Experimental Television System"
RCA Institutes Technical Press, pp. 253-254, July, 1936.
2. V.K. Zworykin, G.A. Morton, "Television, The Electronics of Image Transmission," John Wiley & Sons, Inc., pp. 567-568, 1940
|Year||TV Sets in Use||# Lines in Picture|
|1928 & Earlier||Few Experimental||30 Lines|
|1929||Few Experimental||60 Lines|
|1931||Few Experimental||120 Lines|
|1933||Few Experimental||240 Lines|
|1939||Less than 1,000||441 Lines|