CCIR System H
CCIRSystem His an analogbroadcast television systemused inBelgium,Bosnia and Herzegovina,Croatia,Malta,SloveniaandLiberiaon UHF bands, paired withSystem BonVHF.[1][2]It was associated withPALcolour.[1][2]
Specifications[edit]
Some of the important specs are listed below.[3][2]
The separation between the audio and video carriers is 5.5 MHz.
- Frame rate:25 Hz
- Interlace:2/1
- Field rate:50 Hz[4]
- Lines/frame:625
- Line rate:15625 Hz[5]
- Visual bandwidth:5 MHz
- Vision modulation:AC3 negative
- Preemphasis: 50 μs
- Sound modulation: F3
- Sound offset: 5.5 MHz
- Channel bandwidth:8 MHz
A frame is the total picture. Theframe rateis the number of pictures displayed in one second. But each frame is actually scanned twiceinterleavingodd and even lines. Each scan is known as a field (odd and even fields.) Sofield rateis twice the frame rate. In each frame there are 625lines(or 312.5 lines in a field.) Soline 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 forSystem Bwhich is used on the 7.0 MHz wide channels of theVHFbands. 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).
System G[edit]
Many countries use a variant of systemHwhich is known asSystem G.SystemGis similar to systemHbut 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 systemG(on UHF) is the same as systemB(on VHF), simplifying the band-switching circuitry in VHF/UHF televisions.
See also[edit]
Notes and references[edit]
- ^ab"Weltweite Fernsehsysteme (NTSC, PAL und SECAM)".paradiso-design.net.2005.Retrieved6 March2023.[permanent dead link]
- ^abcPemberton, Alan (30 August 2012)."World Analogue Television Standards and Waveforms".Archived fromthe originalon 30 August 2012.Retrieved6 March2023.
- ^Reference Data for Radio Engineers, ITT Howard W.Sams Co., New York, 1977, section 30
- ^Not an independent value: 25 Hz•2=50 Hz
- ^Not an independent value: 25 Hz•625=15625 Hz