WABD's New Transmitter Installation

in the Empire State Building has Many Unique Operating Features

Description of the new Du Mont WABD transmitter installation on the 82nd floor of the Empire State Building in New York City. The transmitting antenna is installed atop the 102nd floor of the building-a common steel tower being employed to support the transmitting antennas of WABD and several other metropolitan area television stations.

In the Du Mont transmitter installation the equipment is arranged in a “U” in order to bypass a large cross-section supporting column located in the center of the room. Despite this arrangement, it was necessary to locate the equipment in such a way that the operating engineer could have a clear view of all front panels and indicating instruments.

When the engineer is seated at the control console, thirteen racks of video and audio equipment, auxiliary to the transmitter, are installed to his right. The Du Mont 5 kilowatt (visual) and 2.5 kilowatt (aural) “Oak” type transmitter is installed to his left while the five transmitter cubicles, or cabinets, are mounted in the wall facing the thirteen racks of auxiliary equipment across the room. Thus the large cross-section column does not interfere with the station operation because of the carefully planned layout.

Metal duct piping and an exhaust system remove the warm air from the 5 kw transmitter cubicles and equipment racks in order to keep the equipment at a safe operating temperature. The transmitter is air-cooled through-out so the warm air radiated by the tubes must be exhausted.

The transmitter console, behind which the operating engineer is seated, contains all of the controls and meters required for normal and convenient operation of the transmitter. The console has provision for placing the transmitter into or out of operation, and for checking its performance under regular operation-particularly with reference to the quality of the incoming and transmitted signals.

In addition, equipment has been incorporated which will permit tracking down and eliminating operating faults and difficulties which may develop during the course of a transmission. All of the essential meters necessary to the operation of both the visual and aural portions of the transmitter are duplicated at the console so that the operator may read them without leaving his position.

A line waveform monitor at the console displays the video waveform on a small cathode-ray tube screen, the horizontal sweep being linear and precisely synchronized at half the line frequency of the video signal, i.e., 7875 cycles-per-second. The horizontal scanning rate is, of course, 15,750 cycles-per-second under American television standards.

The frame waveform monitor, similar to the line waveform monitor, has a sweep frequency equal to half the field frequency of the video signal, or 30 cycles-per-second. The field rate in television is 60 cps.

Thus, the electronic information in the picture, at either the horizontal or vertical frequency, may be viewed by the operator on either one of the two small monitoring cathode-ray tube screens.

A larger picture monitor, which is capable of high resolution and is located at the center of the console panel, permits the operating engineer to continuously monitor the picture being transmitted.

Suitable gain and level controls and indicators are provided at the console for handling both the visual and the aural levels required for proper signal transmission.

A “Monochrome Scanner” is housed in one of the auxiliary racks to the right of the console. This new unit replaces the monoscope camera chain which was formerly used to transmit the station’s test pattern exclusively.

The Du Mont TA 150-B “Monochrome Scanner” not only provides a means for transmitting the station test pattern but may also be used to transmit regular 2” x 2” slides of the type used for advertising messages. These “spot” announcements in slide form may be inserted at any point in the program by merely pushing a button which controls the scanner. As many as 25 slides may be inserted in the magazine of the scanner at one time and the slides can be changed at the rate of one every .2 second, at the push of the button.

This scanner unit is actually a complete signal source for the television station and it is only necessary to provide horizontal and vertical drive and blanking from a standard sync generator to place this equipment in operation. This equipment eliminates the necessity for “firing” up a whole camera chain just to transmit a test pattern or "spot" announcements on slides.

Radio and Television News/April 1952 Scott Helt/Research Dept., Allen B. DuMont Laboratories