Hi Ray, another approach is to coax one half of a dual-head computer graphics card into outputting a 405 line signal directly, all you then need is a modulator.
https://www.vintage-radio.net/forum/...d.php?t=130716
http://www.nostalgiatech.co.uk/Baird%20240%20lines.htm
Mods, I have asked before, could Peter's page above be made sticky?
This technique must be seen as a viable alternative to system-converting from 625.
Graham.
G3ZVT