Originally posted by HarryC
The reason that Futaba can't do negative shift on us is that we use 10Khz spacing so our regulations require the frequency shift to be the same direction. If it was just an inverted PPM data signal then the two frequencies used would be the same for +ve and -ve shift and Futaba would do to us what it does to North America. Futaba can do its negative shift because your regulations allow it because your 20kHz spacing is big enough to cope with frequency shift in both directions. It is the RF that is shifted irrespective of what the manufacturer does about the PPM signal inside the Tx.
It may seem like we have 20KHz spacing, but there are industrial users in between each of our channels. Each channel is only 10KHz wide - just like yours (carrier freq +/- 5Khz).
The shift is only 5KHz, so there is enough room within a 10KHz channel spacing.
LF - if the deviation is symetrical as you suggest, why does the receiver have to match the shift of the transmitter?