Is it possible to setup a Futaba with a Spektrum DX8 asa buddy box? I have the cable for the Futaba to connect to the DX8, but I can't get it to work. Only options under trainer is INH and OFF. So pulling on SH does nothing even though its setup as the trainer switch. The plane I want to use as the trainer is on the Futaba.

Generally on the Futaba radios I used when your looking at the settings in any menu(Trainer included) many are by default Inhibited. When you activate a function the Inh changes to Off or On depending on the position of the switch that is set to work the function. IIRC the Trainer function will not activate if its not seeing a valid signal from the BB.
Which cable are you using? I had the Hangar 9 one I used but IIRC it may not have been bi-directional. IIRC it was designed to use a SPM/JR Master and a Futaba Slave.
Which model of Futaba Tx are you using? I still have a 7C and 9C and the Cable. If I get a chance Ill drag one out and recheck whether or not the cable is bi- directional.
Ive been flying SPM for years now. Its been awhile but I remember having trouble with the trainer system between various Futaba radios. Some combinations would work and some simply refused.

Aerocal brings forward a few good points. Also is good to remember that many radios require you to TURN OFF the slave as it will be powered on when the cable is plugged in. This particularly applies to Spektrum and JR radios.

Rafael

It may be the bidirectional thing. The DX8 powered up when I plugged in the cable, but flipping the switch did not change the 4 channels to on from off. I enabled the four main channels, and none work, so most likely its just a mismatch from the radios. The cable I have is from the RealFlight kit, so it probably is only useful for that. Somewhere I have the JR trainer cable, so will probably just link the Apprentice for training for now, then maybe bind an orange rx for the LT-40.