Dave's Third Crystal Set. — It's A Mystery Set!
Can't anybody stop me?! Yep, I am still at this crystal set thing. I bought more parts and I am ready to go! This set will be based on the "Mystery Crystal Set" published in 1932. I used an updated design provided by Dan Petersen, W7OIL. Dan had discovered a twist in the design to give some extra zip to this radio. This is my first radio using a cylinder coil rather than the spider web coil. I did try the spider web coil, but it just didn't work. The details of this coil are contained in the articles mentioned above. I used some 40/44guage served litz wire for the tuned antenna circuit and some 30 gauge silver plated kynar coated wire for the detector winding. This wire is the type used for wire wrapping, but worked quite well for this coil. The coil form is a salt box, provided by my neighbor Gloria. I cut this in half and wound my coil. I didn't prepare the form by coating it so I hope that the moisture doesn't become a problem.
I went back to Bed Bath and Beyond for another box. When I was there the first
time, I spotted a wooden box, 5x5 inches square on the top and 7 inches deep.
I thought that this would be a good candidate for this receiver as the capacitor
and coil were somewhat different than the previous receivers.
I built this crystal set according to the circuit below. I did add a 33k ohm resistor across the phones connection in case I wanted to use a crystal earphone instead of the electromagnetic type.
The top is made from 3/16 inch black Garolite®. The material was rough cut with a table saw, leaving a 1/8 inch overlap. Then the holes were cut and the top screwed to the box with 4 flat-head wood screws. Then a router was used to trim the edge to match the box. My thanks to Tim Myers, my neighbor for helping me make this crystal set into a show piece, rather than the regular job that I do.
Here is another Australian Style Crystal Mystery radio.
All in all, this radio looks pretty nice, I hope that you agree.
73, Dave - N2DS