@thor anyone can make an RF transmitter or receiver that (barely) works... the trick is making a good and legal one.
I made a transmitter once when I was like 12 out of a 555 timer. It worked on AM, you could hear it on the radio from a few feet away... but being a very unstable square wave it had so many harmonics you could pretty much tune up anywhere and still hear it :)
@freemo i made a transmitter that my AM radio could pick up when i was six
i made sparks with a battery.
but yes, the tricky bit is frequency selectivity and following the laws...
You: Hey look I built a transmitter
Them: Ummm, thats just a low power EMP/jammer
You: Isnt that what I just said?