Personally this is as basic as they come and have a range of 10 miles or more. It won't do voice but will do Morse code and can be constructed from around $1.50 or less in parts.
You will need..
- 1 crystal resonator. I used a 3.579545 MHz crystal which will work in the 80 meter ham band.
- 1 2N3904 NPN transistor
- 1 0.001 uF capacitor
- 1 1K ohm resistor
- 1 100K ohm resistor
- 1 9 volt battery
You now need to connect everything as shown below
Below is the pinout of a standard 2N3904 transistor for reference.
The antenna can be a short length of wire strung up in a tree or somewhere high and the ground wire should be connected to a copper water pipe or the ground pin of an electrical outlet (if you don't know which hole is which, leave the outlet alone and use a copper water pipe)
Tune your radio to the frequency printed on the crystal resonator and you should hear a high pitched tone or a clicking noise as you turn the circuit on and off to send Morse code. You may also find that you will need a radio capable of receiving single side band or CW as some AM radios don't work well with this circuit.
As ridiculously simple as it looks, this circuit is capable of transmitting a signal 10 miles or more and goes to show just how simple a radio transmitter can be.