the traps are capable of adding a notch of -20 db. so even if you don't hit the bottom precisely, a 10 db reduction is all that is necessary to clean it up to the required level.
these are meant to be fixes that work with existing boards : from v1 onwards. i tried to choose a method that was easy to do.
we will need a different post mix if amp design going forward
yes the traps are for 90 mhz and 12 mhz.
the 10 mhz insensitivity is something i will look into today, I havent experienced it. perhaps we should move the trap to tx filters for the 21 mhz to 28 mhz band? the 12 mhz is filtered for the lower bands in any case.
the other place to apply the 12 mhz trap would be the local oscillator output?
another simple mod to be applied is to change R26 and R46 from 470 ohms to 220. the darlington pair was having insufficient current adding to distortion woes.