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For our 10 minute radio, we will need these parts:

A ferrite loop antenna coil In our other crystal radios we wound the coil by hand. In this project we use a much smaller coil with a ferrite rod inside.The ferrite rod allows the coil to be smaller, and it can be moved in and out of the coil for coarse tuning.

A variable capacitor (30 to 160 picofarads) .You can find them in old broken or discarded radios.
A Germanium diode (1N34A) .
A piezoelectric earphone.
A short wire or alligator jumper We use an alligator jumper here for convenience. Radio Shack part number 278-1156, or you can find them anywhere electronics parts are sold. You can use any piece of insulated wire instead.
About 50 to 100 feet of stranded insulated wire for an antenna. This is actually optional, since you can use a TV antenna or FM radio antenna by connecting our radio to one of the lead-in wires. But it's fun to throw your own wire up over a tree or on top of a house, and it makes the radio a little more portable.
A block of wood or something similar for a base

You can see from the photo how simple this radio is, and why it can be put together in a very short time.
The wires from the ferite loop are soldered to the two rightmost leads of the variable capacitor. It doesn't matter which wire goes to which lead.
The germanium diode is soldered to one of the leads of the variable capacitor. Again, it doesn't matter which lead.
One of the piezoelectric earphone wires is soldered to the free end of the germanium diode. The other is soldered to the lead of the variable capacitor that does not have the diode attached to it.
Lastly, the alligator jumper is simply looped around the coil once (if you have a nice long antenna and a good ground) or a few times (for shorter antennas). We'll glue the coil and the wire down later, after we have tested the radio. In the meantime, some sticky tape can hold it onto the base.

That's it -- you're done!