Crystal radio question
If you use a ferrite loopstick antenna in a broadcast-AM (MF) crystal radio, then no external wires are needed for an antenna or ground.  (I built a few when I was a kid, and used them from a second story).

If you use an air coil instead of a ferrite rod for your tuning inductor, then a couple wires, with one for a long wire antenna, and perhaps one for a counterpose, might be necessary (depending on station signal strengths). But both can be above ground.