I have just had the following reply back from RP Comms, I asked them if they had any specific information about setting the bias for the 6900 v6.
Hi Mike
I used the Galaxy\Ranger IRF520 notes
http://www.cbtricks.com/miscellaneou...ssb_mosfet.pdf
check psu set 13.8VDC
Turn Mic gain to zero before proceeding
Set AM mode
Driver 3.8V DC on Gate
PushPull pair each one on Gate 3.6V DC (Gate)
after test check AM clean with test tone 85-90% Mod 1khz test tone
PDF sheet link handy
Kind Regards
Rob