Date   : Sun, 10 Apr 2005 20:13:09 +0100 (BST)
From   : Pete Turnbull <pete@...>
Subject: Re: BBC to VGA Video In/Out

On Apr 10 2005, 19:24, Ian K wrote:
> In article <E1DKegK-0000V0-00@...>,
>    John <blip@...> wrote:

> > I recently purchased an RGB cable for my BBC to connect to the 28"
TV.
>
> > Unfortunately the display is awful, very blurred, which I think is
down
> > to the size/quality of the TV.
>
> It sounds as though your tv is getting too much signal is your lead
fitted
> with dropper resistors.

I think Ian has the answer, especially since John put "VGA" in the
subject line.  A VGA monitor, or a TV with normal RGB, expects an
analogue signal at around 1V peak-to-peak; the Beeb output is TTL
level, which is about 4V peak-to-peak.  You want to throw away 2/3 to
3/4 of the voltage, and the easiest way is to use dropper resistors in
series with the red, green, and blue signals.  Since the input
impedance of a TV is nominally 75 ohms, resistors in the range 150 ohms
to 220 ohms ought to be about right.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York