In just a few hours you can make a completely batteryless AM radio receiver with a range of around 25 miles. Built with a small assortment of components, some scrap wood, and a beverage bottle tightly wound with magnet wire, we call this project Bottle Radio. Similar to other “crystal radio” projects, the crystal in this build is contained inside a germanium diode, which rectifies incoming audio signal. The radio operates on the power from radio waves, and receives signal from a long wire antenna. When this signal enters the diode, it contains positive and negative peaks, however the diode, only allowing signal to pass in the forward direction, converts the alternating current of the signal into direct current. That current then vibrates a diaphragm inside a crystal earphone, allowing you to hear the radio without any visible power source!
If it sounds difficult, it’s not. In fact once you have your parts in hand, this project will only take a couple hours to assemble. Watch the video below to see how the entire circuit works, and we also provide some tips on the project page for extending the range of your receiver using a loop antenna and RF amplifier.
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