Dave's Shortwave Crystal Set (49 Meters) #9
Ah, my first shortwave crystal set! Welcome back friends. I finally got around to that shortwave crystal set that I had promised. The case is one that I bought at the Rochester Hamfest last June. I have two more of these boxes so watch out.
This is a quite simple radio. First, it tunes the 49 meter band. The coil is a 1.5 inch mailing tube (1.6 inch o.d.). I painted the mailing tube with a black lacquer. To prepare the tube, I measure and draw a line around the tube. I then cut it gently with a hacksaw. After it is cut, I use a piece of 100 grit sandpaper and lightly sand the outside edges and inside edges. I then lay the sandpaper on the table and set the tube on it's end over the paper and turn. This gives it a nice edge before painting. This tube is 3 inches long. I used a pair of Keystone Z-Brackets to attach the coil form to the box. The antenna side of the coil is 5 turns of 23 gauge wire. The main coil is 30 turns taped at 20 for the diode. This will allow the receiver to resonate in the 5-7 mhz range. I like using a separate coil for the antenna because the detuning from one antenna to the next is less than if a small capacitor were connected to the top of the coil. All these windings and taps are not very scientific, just the gut feeling from 37 years of hamming. You kind of know when it is right, but not why.
While I am thinking of it, I want to thank all the nice web surfers that have come by and sent me those nice comments about my web pages. I appreciate it a lot and it encourages me to write more.