Sixty years ago, prospecting for uranium was a popular pastime, and the gentleman shown here in the March 1957 issue of Popular Mechanics was doing it right. The accompanying article noted that prospecting could be a lonely proposition, and this project allowed you to bring along a companion who would assist and entertain you without demanding a portion of your claim: You could build this combination radio-Geiger counter!
The basic circuit was a superheterodyne radio, using four tubes: 1R5, 1U4, 1U5, and 3V4. The Geiger counter used a 1B85 Geiger tube from the Victoreen Instrument Company. The filaments ran off two cells, and a 45 volt battery supplied the B+. Since 45 volts wasn’t quite enough for the Geiger tube, the circuit used an transformer and spark-gap circuit to charge up a capacitor to a higher voltage. The is was accomplished with a pushbutton in series with the transformer’s primary. You would pump the pushbutton for about 30 seconds to charge the capacitor, which would allow a sufficiently high voltage for the Geiger tube.
The output of the geiger counter went to the audio section of the radio, and when you hit uranium, you would hear the clicks from the speaker.
In the diagram below, the radio is shown in black and Geiger counter in red. The magazine also noted that if you already had a suitable portable radio, you could add the Geiger counter circuit.