I'm building a model submarine with various sensors and other features. The number of controls (channels) I'll need (in the 40 Mhz band,) is quite a lot more than is normally available in a set commercially.

There are obviously a number of options here:

a) buy a commercial radio control set and modify ('hack') it to take the extra channels (in practice, maybe just using the transmitter portion);

b) find an electronics self build rc kit/design and adapt that;

c) find ready made tx/rx 40 MHz modules and use those as the basis for the design;

d) find a commercial radio control set that has provision for an external input with many channels.

Note that I have fair electronics knowledge but to save time and effort and not to reinvent the wheel (also to ensure a legal radio setup) I'd rather invest in a soundly designed tx.

As another issue, it would be very handy to have a bidirectional link, that is, receive sensor and other data back from the sub, again, in the model 40 MHz band.

It's a long time since I have played with model rc, so I don't know the market for this kind of stuff very well. I've found some gear in the 2.4 GHz band range, but this is unsuitable for a model submarine.

Has anyone experience in this area, know a business that offers self build 40 MHz radio kits or have any other helpful pointers?