Ian Harris 11

Hi,I've purchased a frsky to convert some old transmitters.It all sounded simple with just 3 wire's to connect.Not so simple,it apears i need a ardunino to create ppm.I have an old Horizon hs6e,Macgregor 4 and Futaba M6.If you could point me in the right direction,maybe which Arduino and which script to use i would be very grateful.