ORIGINAL: fizzwater2
I don't believe Spektrum ever made a 72MHz FM receiver.
Airtronics used the same shift as JR, if I remember correctly.
You are of course correct regarding Spectrum being 2.4 only. I tend to refer to JR and Spektrum as the same animal because in every other respect, they are.
I have had JR and Futaba for many years. JR uses Positive Shift and Futaba/Hitec uses Negative Shift.
On 72Mhz, both Hitec and Futaba are Cross Compatible, except for PCM.