jmluber writes in with another radio project -
In the old days, people used radios that used a germanium diode (crystal radio) to receive am radio without the need for a battery (the radio wave powers this type of radio). This site modernizes that concept by showing you how to build a shortwave radio that utilizes a germanium diode.
Build a crystal shortwave radio – Link.
Make a Foxhole Radio – Weekend Project Podcast – Link.
Make a Foxhole Radio – Weekend Project PDFcast – Link.