You say that you are faily new to electronics. Building a 9 channel transmitter/receiver is quite an ambitious project, maybe something simpler first :wink: .
I have been in that game a long time but still would prefer to adapt something already available for that use before trying to re invent the wheel so to speak.
What range do you have in mind?. Perhaps you could adapt remote garage door opener transmitter/ receivers. They often have a selective range of codes , giving the possibility of multiple channels. And they are type approved, avoiding any legal hassles with radio frequency transmitters.