Dave Woodman wrote:
> Gary Hildebrand wrote:
> > Okay, composite video is the complex waveform that defines NTSC as found
> > in any television station. [ ... ]
>
> Except, of course, in those large parts of the world that use PAL, and other
> parts that use SECAM, and....
Thanks for pointing that out!
Just to add a bit of technical info, in the PAL-I system, as used
in the UK, the composite video is inverted before being amplitude
modulated onto the carrier. That means that the sync pules are
peaks of high-amplitude radio signal and bright areas of the
image are low-amplitude signals. The reason for this is to
reduce the average RF power required at the transmitter. Quite
a clever idea, really.
Our sound sub-carrier is at 6MHz from the main vision carrier,
FM modulated. The PAL colour subcarrier is at about 4.43Mhz.
The radio channels used for broadcast TV are in the UHF band,
and typical 1980s modulators were tuned to Channel 36.
--
John Honniball
coredump_at_gifford.co.uk
Received on Sun Jun 16 2002 - 12:23:11 BST