Geoff's Projects Page
Trash Can Radio
with Fools Gold Detector
I wanted to make a radio that was very simple to construct so that anybody could make it from readily available materials and parts. I thought it may be useful if there was for example an emergency survival situation or the networks had broken down or you were marooned but really just a nice piece of fun to construct in the holidays. It really works and is quite listenable
This radio was made from what was basically around in any domestic house ie Paper clips pencil Cokacola can cotton reel curtain hooks an elastic band a safety pin and a breadboard. The only thing that was bought by me was some wire but this could have easily been obtained from an old broken down domestic appliance transformer ie from a microwave oven.
The most critical item to make was the main tuning coil this was wound on a 6 inch long by 3 inch diameter piece of drain pipe. I stuck to my old favorite circuit and type of coil. This is the' Mystery Crystal radio' circuit and coil (see link to constructional details below ) . It is a very simple and very sensitive circuit and actually works better with a piece of Iron Pyrite (Fools Gold) than a crystal diode like the 1N34 . On the diode there was overlapping of stations but not so on the fools gold.
The main tuning capacitor was made from a cokacola can. I cut away half of the can area. I then stuck another piece of coke can onto a piece of clear plastic Christmas cake wrapper with double sided tape. This was then secured to a CD disc also with double sided tape. The whole thing was made to rotate on the can thus producing a crude but quite effective tuning capacitor The capacitance swing was from 100pf to 400pf. This enabled me to tune most of the medium wave band with ease.
The detector was made from a very large piece of iron pyrite and an elastic band two curtain hooks and a nickel plated safety pin all mounted on a disc of wood . I had not tried such a large piece of pyrite before in a detector but there seemed to be no deterioration of sensitivity due to size or positioning of the safety pin. I found the best part to just touch the pin on was not the flat faces of the crystal but the small crystaline structures or clusters. You do not need a firm pressure but just a light touch contact even just a resting position is the best. It is by no means as fiddly as the Galena type detectors and seems less prone to vibration.
All the set wiring was tucked away under the breadboard , there were only about half a dozen wires anyway. This was a nice little project and I really enjoyed making and listening to it over the Christmas holidays.