Craig Smith (South Milwaukee, WI) writes:
With all of the junk I accumulated, I thought it would be neat to make a crystal radio as a low impact project in the evenings. I unwound the coated wire from a small useless 115V brushless motor that I almost tossed out several times, and wound it about 130 times on a piece of 1.25″ PVC. The clear coating got scraped off where the tuner slides back & forth. Then I made a (nicer that I intended) wood frame for the apparatus, as well as some darn nice scrap brass connection plates for the bolts and burr nuts.
A 40′ scrap wire antenna runs down my fence and into my basement to the slide tuner bar. A small wire also connects the tuner to the crystal pot. A good household ground and one of the earphone wires connects to one of the coil ends. Choose one or the other, one will be better than the other so stick with that one and ignore the other. The second earphone wire connects to the crystal pinpoint contact. To find the ‘sweet spot’ on the Galena (or Pyrite fools gold) crystal which acts as a diode, the contact needs to be positioned about the crystal to find the best spot. One can also just use a nice old glass Germanium diode instead. With a pair of amplified computer speakers instead of the crystal earphone, I can crank it up quite loud. Something about the warm mellow sound of AM radio makes a workshop feel like home.
BTW: For those who are unfamiliar with crystal radios like this, there is no external power source. The radio uses collected radio waves to power the unit.
More great projects from Craig Smith: