High Performance Crystal Radio

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.

This is certainly not the smallest crystal radio we’ve seen. But a lot more people than you might suspect take crystal radio development pretty seriously.

11 thoughts on “High Performance Crystal Radio

  1. I recently used a powered speaker on a crystal set instead of the high Z earphone. It made the thing so much easier to show-and-tell that my son actually showed a little interest. Wish I had thought of it years ago.

  2. Speakers on the ceiling are for Muzak only. For years WBAA AM had an “infinite” bandwidth monitor on it’s AM signal in a monster in-studio monitor. You could hear a 120 mile away station weakly in the speaker at ear height front and center that was 30 kHz away from their frequency. WBAA went to 20k! Hifi!
    No more,they offer HD crap. Lofi and 20 k of modem noise on air, for 64kbps of sometimes stereo or mono garbage.

  3. Crystal radios rock! The thought of receiving a station from over a thousand miles away using NO power input is a concept that most people have a hard time understanding. This set up is pretty cool. If you are interested in doing this, don’t worry that is needs to be this complex – Chris is very advanced and had likely been doing this a long time. You can start out building a really simple, one board set and get exciting performance from it. I built one with a cardboard coil, a tuner from an old radio, no soldering, and a $2,00 earphone and pulled in stations from 800 miles away late at night.
    There was even a radio known as the ‘foxhole’ radio. WWII soldiers built them using razor blades and pencil leads to listen to stations from the front lines. NOW THAT WAS AN IMPRESSIVE HACK!

  4. I have for some reason never tried it, but apparently the coolest zero external power(except the rectified RF) crystal radio amp/speaker is to wire up a kerosene lantern, the infinitesimal energy reacting through in the high impedance charged plasma of the flame is physically modulates it to generate sound.

  5. That is an amazing radio build!

    I was a bit surprised to see the ground connection. Something I have read many times in ham radio literature is that grounds should be done with flat ribbon shaped straps rather than round wire. The reason is that flat strap gets you more surface area and RF due to skin effect mainly travels the surface. I wonder if that would be any improvement here?

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