Withing few hours, provided you have the right components, you can build your own RC transmitter.
First, an important component is the transmission itself. Any module with PPM signal as input can be used. For its low cost, I choosed the Assan module (Hack version X8D) with Assan receivers. Cool price and so far works fine. It is powered with 5V.
The transmitter box is a very low cost transmitter such as those sold for RC simulator (FMS) http://www.flashrc.com/bmi/2637-gamepilot_boitier_simulateur_usb.html . Remove everything except the sticks and switches of course:
The micro processor is an Atmega 644 DIP, with the external crystal and 2*22nf condo. It must be flashed with the RCHv2 software:
Two small board are screwed in the plastic box, one for the micro-controller, the second one for the micro SDcard and the 5V power regulator. Do not forget the led also on the transmitter front.
One the right side, the UART plug to connect to the PC for the radio configuration (it's hidden on the picture between the protoboard):
Connect all the sticks, switches, the Assan module and SDcard board together:
And that's it, the last step will be to close the box and to configure the micro processor with the PC to set the mixers and settings: