In that case, the best experience in my opinion is to DIY one of the simplest radio receiver, that is, a super-regenerative or similar one that could be built off a single transistor/jfet and a high impedance headphone. Or, to make things cleaner, a couple transistors where 1st one acts as antenna preamplifier (and -very important- to prevent the other transistor oscillations to be radiated by the antenna). It's a very simple project that can be built on a breadboard in an afternoon, encourages experimenting and teaches a lot in the process.