The plans for this little one-tube regenerative receiver appeared in Shortwave Craft magazine 80 years ago this month, May 1936.

It runs off household current, using a 12A7 tube, which is a dual tube containing a rectifier and pentode. The rectifier supplies the B+, and the pentode is a regenerative detector. Plug-in coils are used, for either the broadcast band or shortwave. The article recommends starting out with the standard broadcast band, where tuning is less critical. Once the operation of the set was mastered, then the builder could order a set of coils for the shortwave bands.

The filament voltage is supplied from a “curtain burner” line cord, with 350 ohms of resistance built in to drop the line voltage down to the 12 volts required by the tube.  The circuit diagram is shown below.  Filtering of the rectifier output is accomplished with a dual 4uF capacitor in series with a 50,000 ohm resistor.  A modern recreation of this circuit would probably make use of a heftier electrolytic capacitor.

As with any AC-DC set, some caution is called for, since many of the components, and possibly the chassis, will be exposed directly to the “hot” side of the line current.

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