It works
I used the JR circuit on
www.customelectronics.co.uk
Due to availability of some old resistors i used some different values then the ones on the website :
- For the transistors i used the common BC548 and BC558.
- The 22k 's became 18k 's
- And the 470k became 390k
In the radio there is one wirebundle (black-yellow-red) going from the lower circuitboard, to the circuitboard with the crystal and antenna. The black wire is the ground and the yellow wire is the signal wire to use (red is power, but you don't need it).
When you open the radio and look on the crystal-circuitboard, you can see that they 'forgot' a component at the lower left (2 times 3 holes not used). I guess this will will be used for the buddy connection in more expensive versions of the transmitter. But you can now
use these holes for the FMS-interface : Use a left hole (=ground) and a center hole (=signal), from the first or second row, doesn't matter which, they are connected on the bottom...
Good luck to all other X412 users...