ORIGINAL: khodges
I know, it doesn't have a jack for "buddy boxing", but it isn't all that difficult to pass the Tx back and forth, as long as you follow the "three mistakes high" guideline. I've played with the system a little, it's an easy system to get used to; there are already three of the DX-7's in my club, and tomorrow there will be four.
Really? The manufacturers are going to be shocked to hear this as they are installed in them at the factory. Someone must have stolen them from the boxes you saw.
The DX-7 "buddies" with JR radios of most types. JR actually produces these radios for Spektrum too so you can see why. The standard JR mono-pin buddy cable is used. All you really need to do is make sure there is a JR type buddy box available for you instructor to use which could include the Quatro even for a simple trainer. Stay away from mixes and dual rates and such as the buddy box may not be able to emulate those features.