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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 20th Jun 2005, 7:48 am   #21
ppppenguin
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Default Re: Decca Bradford chassis, help wanted

Some clarification:

PAL I (not PAL 1) is the variant used in the UK, Ireland and South Africa. The only significant difference from PAL B/G is that the sound carrier is 6MHz from the vision rather than 5.5MHz.

60Hz PAL is one of those odd hybrid "standards". In the UK we have so-called multistandard VHS machines which can replay NTSC tapes for display on a PAL TV. They convert the colour from NTSC with 3.58MHz subcarrier to PAL with a 4.43MHz subcarrier. The field rate stays at 60Hz so you may need to adjust the field hold on the TV or the picture height may be wrong. Line scan rate is almost the same for PAL and NTSC so there is no problem here. There are other odd hybrid "standards" that exist for similar reasons. Thes include NTSC with a 4.4MHz subcarrier. Don't confuse these "standards" with PAL M and PAL N which are proper standards used in parts of south America.

Part of the reason for having these "standards" is that colour conversion is fairly simple while field rate conversion is much more complex. Simple conversion uses a framestore with field dropping or repeating. This gives odd effects on moving images. The next step up is interpolation between fields which can give very satisfactory results. The most sophisticated converters use motion estimation to give excellent results at a very high price.

You can buy converters at all price points from £200 to £50000.
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Old 21st Jun 2005, 3:39 pm   #22
Sideband
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Default Re: Decca Bradford chassis, help wanted

There is one more 'Hybrid' version I've just thought of that I have seen written as PAL I1. That is the Southern Ireland variant that is basicaly PAL I at VHF rather than UHF. It still uses 6Mhz sound. Northern Ireland is the same as UK mainland.



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