My experiences- How to build a crystal radio

I recommend you to read and understand the basic theory of crystal radio published on this article:

Making a batteryless/powerless radio is a great fun, but there are also some difficulties.

The most difficult part is making an inductor. When I made my crystal set, I simply took out a ferrite rod from a broken radio and wound enamelled copper wire over it. The wire can be from 25SWG to 30SWG. Regarding the number of turns, just wound wire(2 times) covering 90% length of ferrite rod. There is no exact formula for this. Then, simply connect other components as shown in the figure:

radio sch

You can use either OA47 or 1N34 Germanium diodes for this experiment.

The crystal receiver looks like this:
crystal earpiece

Some important notes:

* You cannot get FM signals with this receiver set.

* You will not hear any signal if you connect a general earphone that you use for walkman or skype.

* The closer you are from an AM station, the better radio signal you receive. If you are in a distance of 2-3 kilometers from the station, you don’t even need a long antenna. When I was a teacher, my college was near to AM radio station, so it was easy to demonstrate a crystal radio without antenna and ground.

* If you do not have a crystal earphone, you can use a general piezo speaker that you can get inside a musical greeting card, like the shown below.