ORIGINAL: Imac Kiwi
On 72 Mhz JR and Airtronics use positive shift, Hitec and Futaba use negative shift. This only works for fm (ppm) modulation. Each radio manufacturer uses different encoding for PCM modulation. Outside of USA, we use frequencies other than 72mhz. On PPM they work with each other in my experience. I am not a radio tech, so further input from qualified persons would be welcome.
You are correct for the USA. The ACE MicroPro 8000 was natively negative shift also, but the latest firmware allows selection for the shift. Some Airtronics and Hitec do also. Only JR and Futaba have been hardheaded about allowing the user to select. BTW, it is interesting that Futaba is negative shift on 72 MHz but positive shift on 50 MHz.
It is my understanding that outside the USA all radios shift the same way.