405 lines from Raspberry Pi 5

[OldTVEnthusiast]

While I’d happily tackle bit banging on an 8 bit Atmel I’d be cautious about attempting it on a single board computer and grappling with issues that the operating system might throw up in terms of timing. The address shifter is the easy way out!
The idea of a varicap based filter is good, and output filtering is something I should pay more attention to generally, I live too close to Gatwick to start radiating harmonics in the low hundreds!