Q&A for How to Make a Crystal Radio

Yes, you can. These might be expensive, though, and it might take some of the fun out of making your own.

The energy collected is very small, in the order of a few dozen microwatts (millionth of a watt). It depends on how close the transmitter is to the antenna, the length of the antenna and the losses in the components. The wavelength of a radio wave in the AM broadcast band is in hundreds of feet; at 740 kHz it is 1329 ft (405 m), and a 50-foot antenna will capture only a small fraction of its energy. It is not a practical source of power. A small LED of 10 - 20 milliwatts (thousandth of a watt) would need thousands of crystal radios and their associated antennae to light it.

Germanium diodes work better because of lower voltage to make it work. The voltage drop across a diode when it is conducting changes with different materials and construction. Germanium diodes (e.g. 1N34A) have voltage drop around 0.1-0.2V. For silicon diodes (e.g. 1N4148) the voltage drop is around 0.5-0.7V. Schottky diodes (e.g. BAT85) have a silicon and metal junction, and have voltage drop of about 0.15-0.25V. The lower voltage of germanium and Schottky diodes improves the sensitivity of the crystal radio for weak signals, while using a silicon diode may result in no sound at all.

Any kind of wire that is flexible and that is easy to handle will do. For example, insulated stranded wire, 24 to 18 AWG (0.5 - 1.0 mm) will do. Thicker wires are harder to bend, smaller wires are more flexible but are easy to break when screwed down. It is possible to use bare wire, but make sure they do not touch anything else in the circuit, it makes adjusting the capacitor more fiddly.