This musician-electronic hobbyist, shown on the cover of the April 1955 issue of Popular Electronics is playing the Theremin that he built according to the magazine’s plans. The magazine stressed that the project was not for beginners, but for those with some electronic experience, it was fairly easy to assemble.

Once built, the owner could use the instrument to play music, or to provide background sound effects for amateur theatricals. “A complete show can be produced by combining its abilities to emit both music and sound effects.”

The instrument depended on hand capacitance on the two antennas. The one marked “T” was the tone. The variable capacitance changed the frequency of an RF signal generated by an oscillator. This was mixed with another oscillator to produce a heterodyne which was amplified. The “V” antenna controlled the volume.

Several column inches were devoted to instructions on how to play the instrument, the final one being: “Practice! Practice! Practice! Practice!”  To give an idea of what the instrument sounds like for someone who did practice, here’s what a 1929 Theremin sounds like:

Building the Theremin today with modern solid-state components would probably be simpler, and definitely much cheaper than 65 years ago.  You can buy a Theremin already assembled.  If you just want to experiment with the concept, you can start with this inexpensive kit.

Yesterday, we showed this diagram from the April-May 1970 issue of Science & Electronics magazine and asked what current is shown on the ammeter.

The puzzle is easier than it appears, once you see the trick.  The answer is 3 amps.  Despite the confusing diagram, the three resistors are wired in parallel, so the total resistance is 1 ohm.  You can do the math in your head using the “reciprocal of the reciprocals” method.  1/3 + 1/3 + 1/3 = 1, and 1/1 = 1.  To get the current, it’s 3 volts divided by 1 ohm, which equals 3 amps.

Today’s quiz appeared 50 years ago this month in the April-May 1970 issue of Science & Electronics magazine. What is the current shown on the ammeter?

This was sent in to the magazine by a reader who was given the question during a job interview for a position as an electronic technician. We’re guessing he didn’t get the job, since he wrote to the magazine to explain it. If you’re also stumped, we’ll have the answer tomorrow.

I’ve never had the opportunity to visit yet, but my bucket list certainly includes a trip to the headquarters of Larsen E. Industries. The company was founded by technical genius Larsen E. Rapp, WIOU, sixty years ago this month. This announcement of the momentous event appeared in the April 1960 issue of QST.

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