Gidday Darryl
Note that the output of the modulator is on a low
VHF frequency and you can catch noise from the
synthesizer. It is good to make it stand alone,
because the logic in your converter makes noise
too.
The synthesized oscillators have much phase noise
(every vco has this) so you will decrease the quality
of the converter.
The different TV systems have all their advantages
which can be pointed out in a special modulator
stage
. With a universal modulator you can not do
this and it will allways be a compromise for everything
.
I think for GB it is a good solution to have a modulator
that makes London and Birmingham at the same
time. Then you can connect all TV's on it and you don't
have to switch and connect around
.
Kind regards
Darius