Science Buddies: "Ask an Expert"

I build the crystal radio and it doesn't work. I wrapped the coils on a glass bottle. One of the coils in the middle moved out of place when I was sanding and it wont go back in its spot. It sits loosely on top of other coils. Could this cause it not to work? I turned the bottle around and sanded a new strip. Will having 2 sanded strips cause it not to work?
thank you

Powfam06 - I'm not sure what radio design you are building, but it sounds like you have a tightly wound coil around your coil form, and the sanded strip you refer to is to allow a contact wire or slider to move across the bared copper coils to tune the inductor. If you rewound the coil after it had been sanded a first time, it's very possible that there are opportunities for the coil to 'short out' as adjacent turns possibly come into contact with each other. To be safe, you might want to rewind the coil with new, copper magnet wire, fix it in place with some adhesive, a few lines of 'hot glue' or other means of securing it to the form, then lightly sanding a narrow strip for the slider. I may be assuming the wrong design here, but that's what it sounds like to me.

Rick Marz