CCIR System H

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CCIR System H is an analog broadcast television system primarily used in Belgium, the Balkans and Malta on the UHF bands.

Television Telecommunication medium for transmitting and receiving moving images

Television (TV), sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome, or in colour, and in two or three dimensions and sound. The term can refer to a television set, a television program, or the medium of television transmission. Television is a mass medium for advertising, entertainment and news.

Contents

Specifications

Some of the important specs are listed below. [1]

System G specifications
Frame rate Interlace Field rate Line/frame Line rate Visual b/w Vision mod. Preemphasis Sound mod. Sound offset Channel b/w
25 2/1 50 [2] 625 15625 [3] 5 MHz. AC3 neg. 50 μs F3 5.5 MHz.8 MHz.
Channel spacing for CCIR television System H (UHF Bands)
The separation between the audio and video carriers is 5.5 MHz. Channel spacing for CCIR television System H (UHF Bands).jpg
Channel spacing for CCIR television System H (UHF Bands)
The separation between the audio and video carriers is 5.5 MHz.

A frame is the total picture. The frame rate is the number of pictures displayed in one second. But each frame is actually scanned twice interleaving odd and even lines. Each scan is known as a field (odd and even fields.) So field rate is twice the frame rate. In each frame there are 625 lines (or 312.5 lines in a field.) So line rate (line frequency) is 625 times the frame frequency or 625•25=15625 Hz.

The RF parameters of the transmitted signal are almost the same as those for System B which is used on the 7.0 MHz wide channels of the VHF bands. The only difference to the RF spectrum of the signal is that the vestigial sideband is 500 kHz wider at 1.25 MHz. Due to this and the extra width of the channel allocations at UHF, the width of the guard band between the channels is 650 kHz (assuming the worst case which is when NICAM sound is in use).

CCIR System B was the 625-line analog broadcast television system which at its peak was the system used in most countries. It is being replaced across Western Europe, part of Asia and Africa by digital broadcasting.

System G

Many countries use a variant of system H which is known as System G. System G is similar to system H but the lower (vestigial) side band is 500 kHz narrower. This makes poor use of the 8.0 MHz channels of the UHF bands by merely increasing the width of the guard-band by 500 kHz to 1.15 MHz. The advantage(?) is that the RF spectrum of system G (on UHF) is the same as system B (on VHF), simplifying the band-switching circuitry in VHF/UHF televisions.

CCIR System G is an analog broadcast television system used in many countries. There are several systems in use and letter G is assigned for the European UHF system which is also used in the majority of Asian and African countries.

See also

A television transmitter is a transmitter that is used for terrestrial (over-the-air) television broadcasting. It is an electronic device that radiates radio waves that carry a video signal representing moving images, along with a synchronized audio channel, which is received by television receivers belonging to a public audience, which display the image on a screen. A television transmitter, together with the broadcast studio which originates the content, is called a television station. Television transmitters must be licensed by governments, and are restricted to a certain frequency channel and power level. They transmit on frequency channels in the VHF and UHF bands.

In broadcasting, a transposer or translator is a device in or beyond the service area of a radio or television station transmitter that rebroadcasts signals to receivers which can’t properly receive the signals of the transmitter because of a physical obstruction. A translator receives the signals of the transmitter and rebroadcasts the signals to the area of poor reception. Sometimes the translator is also called a relay transmitter, rebroadcast transmitter or transposer. Since translators are used to cover a small shadowed area, their output powers are usually lower than that of the radio or television station transmitters feeding them.

Notes and references

  1. Reference Data for Radio Engineers, ITT Howard W.Sams Co., New York, 1977, section 30
  2. Not an independent value: 25•2=50
  3. Not an independent value: 25•625=15625

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CCIR System A was the 405 line analog broadcast television system broadcast in the UK and Ireland. CCIR service was discontinued in 1985.

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