9 cap questions
If you need or want to use all 9 channels now, order a 9CAP. It'll come with the 9 channel, R149DP. If you only need 8 FM channels now, order the 9CAF... it come with an 8 channel R148DF and costs much less. PCM is more precise, therefore more expensive.
Regardless of the AP/AF suffix, the part you hold in your hands is the same, a 9C transmitter. It is able to switch from FM to PCM1024 (not the old PCM512) and back via software switches. Unlike less sophisticated models, you can change transmitter frequency (Channels) by changing a simple plug-in module in the backof the case... the crystal is in the module. Modules cost $54 at Tower Hobbies plus S&H.
You may also use any Futaba narrow band reciever that's on the corresponding channel... so if you have a a Futaba 6 channel receiver in your Tower Trainer, there's no need to change receivers so long as the channels match. The 9c will transmit whatever you program to activate those available receiver channels. The unused transmitter channels will go into crew rest.
It is a dazzling piece of equipment!
By the way, if you go with Tower Hobbies, use ad number 011AE to get $30 off.
Fred