Debug Filter/Modulator board

[g0mgx]

Hi All

I'm debugging a FM board from another Portsdown and am very nearly there....

The only remaining issue is when the SR is >=1000 (and using LC filters) the output spectrum looks like this:



Can someone cleverer than I point me at the part of the circuit I need to be checking?

I'm stuck!

Thanks very much - any pointers appreciated.

Mark
G0MGX