We’ll admit that [3DSage] has a pretty standard design for a crystal radio. What we liked, though, was the 3D printed chassis with solderless connections. Of course, the working pieces aren’t 3D printed — you need an earphone, a diode, and some wire too. You can see the build and the finished product in the video below.
Winding the coil is going to take awhile, and the tuning is done with the coil and capacitance built into the tuning arrangement so you won’t have to find a variable capacitor for this build. There is a picture of the radio using a razor blade point contact with a pencil lead, so if you want to really scrimp on the diode, that works too, and you can see how at the end of the video.
We did like the use of cord ends from a sewing and craft supply store to serve as solderless springs. This would be a great item to print off a few dozen copies and use it for a school or youth group activity. You might want to pair it with an AM transmitter, though so the kids won’t be dismayed at what is playing on AM in most markets. [3DSage] uses a sink for ground — literally a kitchen sink. However, if you try this, make sure all the pipes are metal or you won’t get a good ground and you probably won’t pick up any stations.
We’d like to get some of those springs and make some other kind of starter projects with them like the kits many of us had as kids. This reminded us of the old foxhole radios, found during World War II.