This young woman is mystifying her friends by carrying on a conversation with this black box. Close inspection reveals that the box is, indeed, empty, but voices manage to emanate from it.

Actually, she’s talking to an accomplice in another room, and inside the box is a one-transistor amplifier concealed in a false bottom. It contains a pickup coil, consisting of 2000 feet of #30-34 wire. This is the secondary of an audio transformer, the primary of which is concealed under the carpet.

The two-way capabilities were courtesy of a hidden microphone in her room. The accomplice would hear her voice, and talk back through the box. The whole system is described in the June 1960 issue of Popular Electronics.

For those who don’t like winding the coil themselves, a suitable replacement would be a telephone pickup coil, similar to the one shown at left.

Sixty years ago this month, the May 1960 issue of Popular Science featured this as the next big thing, although it never quite caught on. It was a silent engine for the lawnmower, outboard motor, chain saw, or almost anything else. You would light it with a match. If using it with an outboard motor, it would probably be a good idea to bring along some waterproof matches to avoid rowing back to shore.

Then engine was a variation on the Stirling engine, which alternately heats and cools air, deriving power from the differential pressures.  The Wikipedia article is long and interesting, but the section entitled “Applications” is only three lines long, and doesn’t mention outboard motors, chain saws, or lawnmowers.  You can buy a Stirling engine, such as the one shown at left, and in fact, we have one.  It’s a very interesting novelty item, and we’ve even coaxed enough power out of it to light an LED.  But it’s not something with many practical applications.

In the short story Fallout Shelter Journal by Clement R. Dodge, the North Koreans develop an undetectable submarine by patiently using Stirling engines to recharge electric submarines from thermal vents on the ocean floor.  Maybe they got the idea from this magazine.

The plans for this four-tube superheterodyne shortwave receiver appeared 70 years ago this month in the May 1950 issue of Radio Electronics.

According to the author, the set was the equivalent of a six-tube set, and was pulling in hams on 20 meters from Maine, California, and the Florida coast, all at loudspeaker volume. The trick employed is visible in the picture above, namely, the wire wrapped around the first IF transformer. This was connected to the grid of the 12BA6, and increased the gain through feedback. Plug-in coils were used for band switching, and the author provided coil data for 80, 40, and 20 meters.

The author was Homer Davidson, whose name is familiar as a fairly prolific author of radio books over the years.

Shown here a hundred years ago this month, in the May 1920 issue of Electrical Experimenter, is radio pioneer Miss Abby P. Morrison, later Mrs. Abby Morrison Ricker. In the accompanying article, she described her radio set, which she reported gave her very satisfactory service.

She had two loop antennas at her disposal, which allowed reception of local, Navy Yard, and ship signals on both 600 and 952 meters. She reported that she was able to pull in signals from ships a day or two out at sea, and from various ships up and down the coast. She employed both a crystal detector and an audion.

She doesn’t report having transmitted yet, but she did have a spark coil, rotary spark gap, and 1/4 kilowatt motor generator.

She’s shown in this picture (third from right) competing in a code competition in October 1921. By 1926, Miss Morrison is listed in Radio Broadcast magazine as being an Instructor in Radio at the Y.W.C.A., and one of the authors of “The Easy Course in Home Radio.” At some point, she was the author of a book entitled “Radio Operator’s Primer,” which she revised in 1943 under the title of “Radio Primer.” She submitted these books to General Electric in 1943, which returned them without acceptance. But in 1943, GE published a book entitled “The ABC’s or Radio,” which she alleged infringed her copyright. She sued, and the case was ultimately heard by the U.S. Court of Appeals for the Second Circuit.

Unfortunately for her, the appeals court affirmed the summary judgment granted in favor of the defendant. Ricker v. General Electric Co., 162 F.2d 141 (2d Cir. 1947). The court held that it had examined the record carefully and found no similarities between the two books which could support a charge of plagiarism.

The court noted that “by a judicious process of selection of words extracted from sentences and from the surrounding context, she finds some repetitive expressions. Needless to say, this method is not convincing.” The court pointed out that “the obsessive conviction that all similarities are inevitably plagiarism is frequent among authors.” But the examples cited didn’t hold up.

Surprisingly, I wasn’t able to find much more information about this radio pioneer. In particular, I wasn’t able to determine whether she was ever licensed. In this 1927 directory of musicians, however, she is listed as a soprano who made her debut in Paris in 1925. It notes that she had sung “with San Carlo Opera company and at courts of England, Belgium, and Spain,” and had “appeared in recital and oratorio in New York.” I can’t determine the provenance, other than being an eBay listing, but the photo below apparently shows her in character in an opera in which she appeared.

Sixty years ago this month, the May 1960 issue of Popular Electronics showed how to make this three-transistor portable radio. It was billed by the magazine as a set that could be put together in one evening, and was perfect for the hobbyist who wanted to move on from crystal sets, but wasn’t quite ready for a superhet.

The attractive set was said to be about as big as the ubiquitous pack of cigarettes, in this case, king-size cigarettes.

The set used two 2N170 NPN transistors, and one 2N107 PNP. The first transistor served as detector, with the other two amplifying the audio. The set was said to be sensitive, pulling in all of the local stations with a short wire antenna. For more distant stations, the antenna had an alligator clip at the end, which could be clipped to a window screen or longer antenna. Permeability tuning was employed, with the slug of the loopstick screwed in and out.

Conventional wisdom is that, prior to the Internet, it was impossible for individuals to reach a wide audience. Fortunately, nobody bothered to share this conventional wisdom with Charles Edward Caswell of Concord, N.H. , who wrote, edited, printed, and distributed his own magazine, Friendly Cheer.

This article appeared in Popular Science, May 1940, which noted that copies of the magazine went to every state and 14 foreign countries.

We haven’t been able to figure out what happened to Friendly Cheer magazine, and the domain name friendlycheer.com is still available. So if anyone wants to pick up where Caswell, left off, there’s your opportunity. And if anyone has a copy of the magazine, we would love to see it.

There’s a good reason why this young man dressed up to go ride his bike. That’s because its basket contained a four-tube radio capable of providing loudspeaker volume on local broadcast stations.

Because of its nondirectional characteristics, a four-foot rod antenna was used. Grounding was necessary, but an attachment to the bicycle frame provided an excellent counterpoise.

The set featured a DPDT key-lock switch to keep curious onlookers from running down the batteries. The magazine also advised locking the set to the basket or bicycle frame. The set used three 1N5GT tubes as RF amplifier, detector, and the first stage of AF amplification. A 1T5GT served as final AF amplifier to drive the speaker.

The set appeared 80 years ago this month in the April 1940 issue of Popular Science.

The plans for this handsome four-tube superhet portable appeared 80 years ago this month in the April, 1940, issue of Popular Mechanics. The set was said to be suitable for anyone with even a little radio construction and wiring experience. It used 1.4 volt tubes and was a highly flexible and portable receiver.

For those without metalworking tools, the chassis was available pre-punched and drilled. A loop antenna meant that no external antenna was necessary for local stations.

Wikipedia image.

Today is the 20th birthday of Bartholomew I of Constantinople, the Patriarch of the Eastern Orthodox Church. He was born on February 29, 1940.

A hundred years ago this month, the February 1920 issue of Electrical Experimenter detailed this plan which surfaces from time to time: To get hydroelectric power by piping water from the Mediterranean Sea to the Dead Sea, which lies 1400 feet below sea level.

The necessary tunnel would be 37 miles long, and would pass about 2500 feet under Jerusalem. According to the magazine, the plan would bring electric lights and electric trolleys to the Holy Land.

More information about the various proposals for this project over the years can be found at Wikipedia.