This Crystal Radio Is Made From a Few Components and Old Credit Cards

What do you do with your old credit cards? You probably cut them up and pitch them. One tinkerer went beyond and transformed his old credit cards into a crystal radio. Billy Cheung has a knack for turning random objects, like earbud cases and matchboxes, into small radios. This time, Cheung converted old credit cards into a working radio.

Though it looks and sounds complicated, few parts were used to create the device. It didn’t require a variable capacity, which can be hard to find. Rather, it uses a variable inductor or variometer to tune into stations. And because of the technology built into the card, no diodes are required.

Instead, the credit card’s smart chip is used as the transformer. The smart chip has an impetus of about 100k. To get it to properly work, you’ll need a step-down transformer to match the impetus of your headphones. Otherwise, all you need to make the crystal radio is an antenna, coil, capacitors, a detector (crystal, diode, zero voltage MOSFET, LED), and some old credit cards. The credit cards not only serve as the body of the radio but also as the dial. You can find the cut-out pattern for the radio dial here.

The result is a unique radio that actually works and sounds pretty clear. It may not replace your stereo system, but it’s a clever way to recycle and reuse old plastic.