Old school detector radio technology meets 21st century 3d-printing. This is a simple to build and use detector radio for the mediumwave band. And yes - it runs without batteries (by only using the transmitted radio energy). We developed this project for a kids day at our ham radio club. It is fun to build and to use - no matter if you're 9 or 99 years of age! For most of the most popular stations in Europe you'll need about 28 turns which gives an impedance of 50 - 180 uH. Frequency range is about between 550kHz and 1100kHz.Things you'll need 1x the set of printed parts (coil housing, chassis, slider and cap) 1x ferrite rod (standard type with two flat sides), length: 4 cm (1.57inch) 1x diode (germanium type) AA 112 or similar 1x ceramic capacitor 470 pF 1x crystal earpiece (very high impedance of about 2000 ohms) 30 m / 98 feet of 0.4 mm / AWG 26 laqued copper wire for the antenna and ground connection. Construction manual That's it! First Contact Stretch out the antenna and connect the ground wire to an earthed device like central heating radiator, water tap or tent peg when you're outside. !NEVER ever to a power socket! Use the slider to find a station. Listen and mark the frequency on the scale. Have fun building and using your own detector-radio More photos and details (in german) can be found on our ham radio website: http://www.df0fkw.datenoase.de