''. Hugo Gernsback first wrote about television in the December 1909 issue of
Modern Electrics and regularly reported technical advances in his magazines. By 1925
mechanical scanning television systems were becoming available, with resolutions of up to 60 scan lines.
Vladimir K. Zworykin and
Philo Farnsworth were developing electronic scanning systems that were the precursors of modern television but these would not be available for another decade. WRNY was second to broadcast television pictures to the general public, after
W3XK in Washington, D.C., and was preceded by several attempts to broadcast television pictures. In 1927 AT&T had demonstrated a system that sent television images and sound over telephone lines. The General Electric Research Laboratory in Schenectady, New York was sending experimental television over their shortwave radio station in early 1928. Westinghouse had a system that would broadcast motion pictures. Several other laboratories were also conducting experiments and demonstrations. The television camera used a spinning disk, commonly known as a
Nipkow disk, which had a spiral of holes used to sweep a narrow beam of light across the subject. The reflected light was picked up by a photoelectric cell whose electrical output would vary with the intensity of the light. This system was often called a "flying spot scanner". The early photoelectric cells were not very sensitive, so three or four would be used with the subject in a darkened booth. Another reason for multiple cells is even pickup of reflected light from the subject. The cell array includes cells in a window formation: One or more cells above, below and on each side of the subject. The television receiver used the output of the photoelectric cell to control the brightness of a
neon lamp. When the photoelectric cell detected a bright spot, the neon lamp's intensity was increased. The receiver also had a scanning disk with the same hole-pattern as the camera, and it spun at the same speed. The result was a small neon orange image (two inch (5 cm) diagonal) of the remote subject. In April 1928, Pilot Electric Manufacturing and WRNY announced that television broadcasts would begin that fall, with Pilot providing the transmitting equipment. Pilot sold receivers, and the Experimenter Publishing magazines provided complete plans to allowed readers to build their own. The system used by WRNY had 48 scan lines with 7.5 frames per second, with the received image was about 1.5 inches (3.8 cm) square. This low resolution picture, without sound, could be transmitted in the 5 kHz bandwidth of an AM radio station. The experimental stations on the shortwave bands could use a 15 kHz bandwidth for a higher quality image. When commercial television broadcasting began in the 1940s, television stations were allotted a 6 MHz bandwidth. High definition televisions commonly display resolution as
720p or
1080i; this early experimental television was a very low definition 48p display. The television equipment WRNY used was designed by Pilot Electric's chief engineer, John Geloso. It was similar to the system designed by Uilses A. Sanabria that was used in a demonstration by
WCFL in Chicago in June 1928. Both systems used photoelectric cells made by Lloyd Preston Garner; a researcher at the
University of Illinois at Urbana–Champaign.
The New York Times reported this successful test and said the regularly scheduled broadcast would start on August 13, although technical problems delayed this until August 21. The receiver was moved to Hugo Gernsback's Manhattan apartment on Riverside Drive about 5 miles (8 km) from the transmitter. At 10 PM on August 14, John Geloso turned on the set and viewed an image of his wife sitting before the camera in Coytesville. There were problems with synchronizing the spinning disk but a clear image could be seen for six or seven seconds at a time. The "Today on the radio" section of the August 21, 1928, edition of
The New York Times showed 9 television programs on the schedule for WRNY. That night, the first public demonstration of WRNY television was held in Philosophy Hall at
New York University to an audience of radio engineers, scientist and newspaper reporters. About 500 people passed before the television to see the image of Mrs. Geloso: "Mrs. Geloso closed her eyes, opened and closed her mouth and moved side to side. The images were about one and one-half inches [3.8 cm] square, but were magnified by a lens to twice that size."
Homemade television receivers On July 4, 1928,
The New York Times reported that in the past two weeks WRNY had received more than 2,000 letters requesting more information about the television broadcast. Hugo Gernsback stated: "The letters have come alike from radio listeners, wireless experimenters and home set builders who wish construction details about the apparatus required to intercept the television broadcast." Television transmission using the shortwave bands could be received in New York City in early 1928, and Experimenter Publishing's magazines had been printing detailed descriptions of television receivers since 1927. The specialized parts to build a television were available that August. A New Jersey radio supply company, Daven, sold a complete television receiver kit for $100; the scanning disk was $10 and the neon bulb was $11.50.
Raytheon advertised their "Kino-Lamp" and "Foto-Cell" for engineers and amateurs building televisions. The complexity of the television was typical of the construction projects published in
Radio News every month so some experimenters had a set ready for the early August broadcast. The publication of detailed plans for the WRNY receiver in October would have increased the number of built sets. The exact number of home televisions in 1928 is unknown, with Hugo Gernsback estimating that the New York area had around 2000 receivers. and
Radio News had detailed plans for building a receiver. However, Hugo Gernsback warned potential viewers that this early television receiver was for experimenters and "radio bugs", and not suitable for the general public. The WRNY homemade television receiver consisted of a modified
TRF radio receiver. This was an AM band receiver for WRNY transmissions, and a shortwave set for other television stations of the day. After the detector stage, the receiver required a three-tube television adapter, consisting of a resistance-coupled preamplifier and a power amplifier, with the power amplifier driving the neon lamp. A typical adapter had two preamplifier stages and one power amplifier stage. The adapter drove a neon lamp and a 24-inch (61 cm)
Bakelite disk. The disk had 48 holes in a spiral pattern, with a neon bulb mounted behind the disk and replacing the radio loudspeaker. The cover illustration of the November 1928 issue of
Science and Invention featured an experimenter operating one of the homemade television receivers, who was shown using a 125-hertz
tuning fork to adjust the scanning wheel speed. Looking through the vibrating tuning fork, a stationary line pattern on the hub indicated when the wheel was spinning at 450 RPM. The proper speed is not the only requirement, as the receiver's disk must also match the angular position of the television station's scanner disk. (Most mechanical television stations used scanners instead of cameras to pick up the talent.) To make both disks align, the viewer pressed a button to adjust the receiving disk's speed. With homemade sets, maintaining synchronization was a major concern. A receiver with a fan ("universal") motor required the viewer to manually synchronize picture reception. The scanner at the television studio used a synchronous motor. With the same type synchronous motor, the receiver is far easier to keep in step, which is made much easier if both the studio scanner and the home are running off power from the same AC power grid, for with synchronous motors on the same grid, receiver sync is automatic, and the user must then only frame the picture. The variable resistors (R6 and R7 in the construction schematic) controlled the motor speed. The switch boosted the speed of the disk to synchronize it with the camera. To achieve 7.5 image frames per second, the receiver's disk, being rotated by standard household fan motor, needed to spin at 450 rpm. An external, variable resistor controlled the motor speed. The Federal Radio Commission was concerned about television broadcasts on the AM radio band, and the possible interference with standard audio broadcasts. On November 2, 1928, the FRC limited television broadcast to shortwave stations above 1500 kHz. The broadcast would be limited to a 10 kHz bandwidth and for periods of not more than one hour per day. They were not allowed between 6 PM and 11 PM. The commission would review television broadcasting in January 1929. == See also ==