How do you made a simple radio?

Answer 1

Here is the absolute simplest possible:

-- Buy a germanium diode.
The smallest and cheapest you can find, but it has to be germanium, not silicon.
(I can't give you the actual name of an actual store on this website, but I'm thinking
of a source that probably has them, and its initials are Radio Shack. I just looked
on their website, and found the correct item for under $2. I was hoping to find it
for around 10¢ but I guess those days are gone.)

-- Connect the diode between the two wires from an earphone.

-- From one end, connect a piece of wire to a cold-water pipe in your house,
or a metal post stuck in the ground.

-- From the other end, connect the longest piece of insulated wire you can get.
Drape it around your room, or hang it from trees, or zig-zag it around the yard.
Then don't connect the other end to anything.

You may have to be very close to the radio transmitter tower, and it may be very
soft in the earphone, or you may even hear two or three radio stations at the same
time. But if you have good ears, then sooner or later you WILL hear one or more
AM radio stations in the earphone.

Answer 2

A crystal radio is the distilled essence of a radio. It has very few parts, it needs no batteries or other power source.