Seventy-five years ago this month, the February 1947 issue of Popular Science carried plans for a number of crystal sets under the heading “Crystal Sets: The First Word in Radio.” The science of radio had made great strides in one generation, but the magazine noted that the generation of engineers and technicians had all grown up on crystals.

Despite those advances, the humble crystal set had never passed out of the radio picture. Beginners and those who like doing a lot with a little found the circuits inviting. The example shown above was a radio-phonograph, and the magazine noted that a (piezoelectric) crystal phono pickup could drive a set of headphones just as well as a crystal set. While the design shown here used an electric motor, a clockwork turntable could replace it, making a radio-phonograph independent of any power source.

The set shown at left was said to be superselective, and the one at the right was an ideal portable. For use while camping, it needed only a long spool of wire and a stake for the ground. Finally, the set below added one tube for a stage of audio amplification.

From 75 years ago this month, in the January 1947 issue of Radio News, here are the latest radio offerings from Minerva Corporation of America, located at 238 William Street, New York, close to the Manhattan approach to the Brooklyn Bridge.  The site appears to be very close to the current location of Spruce Street School and the New York by Gehry apartments.

Fifty years ago this month, this gentleman was pulling in a shortwave program on his Hallicrafters S-120A receiver, and the excitement of his hobby was shared in a feature article in the January 1972 issue of Popular Mechanics.

The magazine noted that the hobby was enjoying a resurgence, since relatively inexpensive receivers had replaced the costly and rather crude-looking earlier models. There were numerous compact, smartly styled sets between $50 and $200, including the one shown above, which retailed for $79.95, and could run on either batteries or household current.

The article outlined the differences between receivers for international shortwave, and those for VHF-UHF signals such as police radio. It warned that the most sensitive communications receivers might cover only the ham bands, and “unless you’re interested in getting into amateur radio yourself, listening exclusively to ham talk can be a bit dull.”

Eighty years ago, the January 1942 issue of Popular Mechanics showed how to put together this versatile circuit. It’s shown here serving as a phono oscillator, and can play records over the home radio. But it also served as a receiver for both the broadcast band and short waves. The set had a single coil, but it was tapped. For standard broadcast reception, the entire coil was used, but for short wave, most of the coil was shorted out. The set could drive a loudspeaker, although for shortwave use, high impedance headphones were recommended. A pilot light served as a fuse, to protect the tubes in case of short circuit.

This mad scientist, shown in the January 1947 issue of Radio News is probably either George Floyd, W2RYT, or H. Donald Wells, W8LWD, drawing an arc from their newly constructed 1 kW transmitter for the then-new 2 meter band. They apparently didn’t worry too much about RF exposure back then, since he is drawing an arc from the antenna, which is mounted directly on the transmitter. In fact, the article points out that when making measurements of current and voltage in the transmitter, you shouldn’t leave the meters there too long, since they might be damaged by all of the RF that is floating around.

The transmitter is simplicity itself, employing two GL-592 pliotron tubes. According to the authors, the set oscillated the first time it was tried, and they were convinced that “only an order from the FCC would stop the oscillations.” There are few components, as you can see from the schematic below. Tuning was accomplished by adjusting plugs in inductors consisting of 15″ long half-inch copper pipe. It would probably be a good idea to wear thick gloves when making frequency changes, since the B+ was around 2500 volts.

We should mention that kids should not build this transmitter at home. There are a number of obvious safety issues, such as the exposed high voltage and the high RF fields. In addition, it probably wouldn’t meet current FCC spectral purity rules. In other words, an order of the FCC has stopped the oscillations.