As I was trying to organize things a bit in my “office”, I happened to unearth a bit of nostalgia. This is my first crystal radio.
I built this thing after reading about it in some old book. It’s probably about 25 years old. It uses a germanium diode from an old TV set I had taken apart. I’m pretty sure the terminal strips are also from the TV. It’s hard wired to the frequency of the local AM radio station. The capacitors were probably bought from Radio Shack. Based on the frequency and capacitance values, I had calculated the proper number of turns to wind on the high tech coil form, made from a half inch wooden dowel. The coil and some of the wiring are attached to the substrate material (piece of plywood I found in the back yard) using a combination of masking tape and staples. It turns out masking tape doesn’t stick to unfinished wood well enough for this application. The black wire connected to the antenna, which was just more wire dropped from my bedroom window. It also had an earth ground connection which was attached to the face plate screw on a handy electrical outlet. That made a huge difference as I recall. It worked the first time too. It probably helped that there was only one radio station easily available in the area and that these units don’t have much in the way of selectivity. Overall, it was a fantastic, simple project to introduce a kid to electronics.