Seventy years ago this month, the December 1950 issue of Popular Mechanic showed how to put together these three crystal sets. All used the venerable (and still available) 1N34 diode. The first was the most basic set, but used a coil and variable capacitor for tuning.

The second featured greater selectivity, since in included two resonant circuits. For convenient tuning, the circuits used a ganged variable capacitor. The two L-C circuits were linked with with a “gimmick” capacitor consisting of two insulated wires twisted together. The article pointed out that a longer capacitor would result in greater volume, but a shorter wire would yield greater selectivity.

The final circuit was optimized for sensitivity, and would pull in the weak stations with two detectors running in a push-pull configuration.

All of the sets were said to have a range of about 40 miles.

If you’re thinking of recreating one of these circuits, see our crystal set parts page for ideas on tracking down the parts.