Date   : Wed, 24 Oct 2007 15:19:20 +0100
From   : francis@... (Francis Devereux)
Subject: OT was Re: UM1233 TV modulators...

On Wed, Oct 24, 2007 at 03:26:57PM +0200, Anders Carlsson wrote:
> Pete Turnbull wrote:
> 
> > Normally the signal is indeed monochrome,
> 
> Is there a good reason why this is the case? Is the video signal inside the 
> computer splitted into luminance and chrominance and at one point (inside 
> the RF modulator?) merged together? How about the RGB signal, I would expect 
> that is the main signal that is converted to composite video/RF. The only 
> practical reason I can see is in case the BBC Micro can be used on a NTSC 
> display that won't display colours correctly, and the colour burst was 
> removed from the monochrome composite to cause as little disturbance as 
> possible.

The green-screen monochrome monitors that I have seen used the composite
connector which would support your idea that the colour burst was not
included to improve the quality of the monochrome signal.  I don't know how
much difference it would make though.  Also, when the BBC was released then
TVs didn't tend to have composite inputs, they usually only had RF inputs so
there would have been little point in providing a colour composite output.
Perhaps Acorn intended that TVs should be connected to the RF port,
monochrome monitors to the composite video port and colour monitors to the
RGB port?

Francis