RomanBlack.com explains in details how to use 433/315Mhz modules for serial communication.
These cheap RF modules usually come in a pair, with one transmitter and one receiver. A pair can be bought on ebay for as cheap as $4, and even as cheap as $2 a pair if you buy 10 pairs.
Much of the information on the internet from people’s projects is sketchy and not very comprehensive. I test these modules out, and show how to get good reliable serial comms direct from USART -> USART, and I also show how to greatly speed up the data rate and reliability by using an alternative bit encoding system.
How to do serial comms using the cheap RF 433/315 MHz modules – [Link]
Fascinating investigation. Why isn’t it better known ?