Get your feet wet with radio frequency transmitters and receivers by working your way through this pair of tutorials. [Chris] built the hardware around a couple of 555 timers so you don’t need to worry about any microcontroller programming. He started by building the transmitter and finished by constructing a receiver.
Apparently the 27 MHz band is okay to work with in most countries as long as your hardware stays below a certain power threshold. The carrier frequency is generated by the transmitter with the help of a 27.145 MHz crystal. The signal is picked up by the receiver which uses a hand-wrapped inductor made using an AL=25 Toroid Core. We’d say these are the parts that will be the hardest to find without putting in an order from a distributor. But the rest of the build just uses a couple 555 timer chips and passive components, all of which will be easy to find. The video after the break shows the project used to receive a Morse-code-style message entered with a push button. It would be fun to interface this with your microcontroller of choice and implement your own one-way error correction scheme.