Mobile Television Unit
Mobile Television Unit
a complex of equipment for transmitting remote broadcasts. The transmitting equipment is installed in a bus. The high mobility of such units and the feasibility of transmitting or recording at locations other than the television studio has resulted in a wide range of applications, including direct broadcasting of events on location. Important political events, sporting events and competitions, theatrical performances and concerts, and on-location reports on factories, plants, kolkhozes, exhibitions, and museums can be transmitted by mobile television units.
Remote television broadcasting in the USSR was first introduced in 1948. Initially, mobile units had two television cameras for black-and-white images. The first mobile unit for color transmission started operating in 1968. Mobile television units are categorized as standard or portable units (walkie-lookies).
The equipment of a standard mobile television unit usually includes the television equipment on the bus; portable television cameras; audio amplifiers and portable microphones; and a service communications system, linking the unit’s staff with the technical and production staffs at the studio and with other mobile units. Standard mobile units also have radio relay equipment for transmitting the video and audio signals to the studio and equipment to supply power either from the AC mains or from a self-contained generator.
Mobile television units usually have four, less frequently two or three, television cameras and six to 12 microphone inputs. The cameras are linked by cable to the transmitting equipment in the bus. The maximum operating distance of the cameras from the bus is 2 km; and of the microphones, 400 m. The portable part of the radio relay equipment, consisting of a radio transmitter that operates on a wavelength of 4–15 cm and a parabolic antenna with a radiation-pattern width or is mounted on the roof of the building closest to the mobile unit and is connected by radio-frequency cable with the control equipment on the bus.
For remote broadcasts, one condition that usually must be satisfied concerns the location of the receiving antenna of the radio reception apparatus in the television studio: this antenna must be visible from the location of the mobile unit’s antenna. For this reason, it is desirable to install the receiving antennas as high as possible. For instance, the receiving antennas of the All-Union Television Station in Moscow are installed on the Ostankino Tower, at a height of 253 m. The maximum operating distance between the mobile unit and the studio depends on the characteristics of the area between their locations and on the conditions for propagation of radio waves; this distance ranges from 30 to 50 km. Television signals from the mobile unit to the studio can also be transmitted through underground radio-frequency cables.
Several telephone lines are assigned for service communications between the mobile units and the studio. Electric power input into a mobile unit is 5–8 kilowatts (kW). Video and audio signals can be recorded by a mobile videotape unit installed in a separate bus. Ordinarily, one or two mobile units are used to broadcast a single program; complex programs may use three or more.
During broadcasting or recording, each mobile television unit is monitored by an operator, who selects the scene or the object to be shown. At his console in the bus, the program director views on the monitors several images obtained by the cameras and selects the desired image, which is then transmitted to the studio. An audio engineer works from a console that is also usually located in the bus. He controls the audio track for the program by switching to the appropriate microphones, which are placed on the scene of the televised action.
L. I. BUKHMAN