The famous galena radio has appeared in countless electronics tutorials and publications due to its simple construction. It also has a wide margin for optimization and is very tolerant when it comes to formats. In fact, a DIY enthusiast named Billy Cheung decided to explore building similar radios using credit or debit cards with integrated chips, since the chip itself can act as a detector in the circuit.
A Brief History of the Galena Radio
History tells us that the rectifying property of a contact between a mineral and a metal was discovered in 1874 by German electrical engineer Karl Ferdinand Braun, but it took 20 years for crystals to be used as detectors for the first time. These advances gave rise to the famous galena radio, a true fundamental force that accelerated the adoption of radio by the public at the beginning of the 20th century, thanks to its easy construction and the low cost of components.
Turning a Credit Card into a Radio
Would you like to build a galena radio today? Well, let's say galena was retired in favor of modern diodes, but the basic circuit has hardly changed. What's more, with a pinch of creativity you can turn the strangest objects into galena radios, including credit or debit cards you no longer use. How does that work exactly? Enthusiast Billy Cheung explains it in great detail, but in relaxed terms, the smart chip on those cards works as a diode when you connect the right points. Watch:
Yes, the video lasts 35 minutes, but it's very reasonable considering that Billy builds his radio virtually in real time, including the variable inductor with the correct number of turns. One detail he emphasizes a lot is the speaker, and he recommends connecting an impedance transformer to step down from the radio's 100,000 ohms to a more useful value (his speaker is 500 ohms).
As always, the final result will depend on the local radio stations, but if you have a couple of cards gathering dust, why not give it a try?
Access the blueprint on GitHub: Click here
https://old.neoteo.com/banda-apex-radio/
