Follow th elinks inside for the wiki with instructions on how to build it, of course you can ask me if you get stuck.
The total cost of my rc receiver-modem was 20$ with parts from Ebay.
Next i will try to adapt the code in order to run inside the autopilot without the need for a
Btw i tested the 100mw Orangerx Openlrs receiver sold at Hobbyking as a rc receiver and i got error free signal 15Km away using a 6db 433 Mhz antenna.
The 1W version i build outputs 664mw at 5v which is normal because for 1W you need 6v.
Also have in mind that the 1W RFM23BP and the 100mW RFM22 modules come in 3 flavors 433, 868 and 915 Mhz so you can build whatever rc receiver or modem you like Here are a couple photos of the receiver-modem.