When you think of a crystal radio, you probably think of something simple maybe built out of household scraps. Not if you are [Chris Wendling]. He recently posted a video (see below) of his high-performance crystal set. He doesn’t take any shortcuts: he has several hundred feet of antenna wire, and uses a cold-water pipe ground system. With no amplifier, a strong signal input is crucial.
The radio has four subsystems: an antenna tuner, a bandpass filter, a detector, and a powered audio output system. He also has a truly enormous system of speakers on the ceiling–this isn’t the crystal radio you made in the boy scouts.
One novel feature of the bandpass filter is that to use it, you slide the coil between the antenna tuner coil and the detector coil. You can also rotate the antenna coil to affect the coupling. The filter is just a Litz coil and a capacitor, but it adds selectivity to the system. If you watch almost fourteen minutes of the video, you’ll be rewarded with the schematic of the unit, by the way.