Monthly Archives: July 2020

Electric Hot Dog Cooker

I suspect many of our readers have independently invented the idea shown here for an easy way to cook a hot dog. You simply run 120 volts through the hot dog, and the hot dog serves as a resistor and cooks itself. This incarnation of the idea was designed by prolific electronics writer Len Buckwalter and appeared in the July 1960 issue of Electronics Illustrated.

This design is a bit safer than what I remember doing. While cooking, the hot dogs are safely concealed inside a bakelite box. They don’t start cooking until the lid is inserted, since the cord is part of the lid, and there’s a TV-style safety interlock.

The young scientist wishing to come up with an interesting science fair project won’t go wrong with this idea. It give a great demonstration of Ohm’s law and the power law. And sharing the hot dogs with the judges certainly won’t hurt in earning that coveted blue ribbon.

Of course, you don’t want to be disqualified by electrocuting one of the judges, so it’s best to come up with some form of interlock.

The venerable Presto Hot Dogger used the same principle to cook hot dogs. It unfortunately seems to be out of production, but they show up on eBay. But making your own is easy, and a lot more fun.

1940 Three Tube Superhet

This young woman and her faithful canine companion are pulling in a program from a distant station thanks to the very sensitive and selective three-tube superheterodyne receiver described in the July 1940 issue of Popular Science,

For added sensitivity, the detector is regenerative. Only one IF coil is used, meaning that the set can easily be aligned for peak performance. If a strong station is present in the area, then the article showed how to add a volume control in addition to the regeneration control shown in the circuit.

1920 Magnavox Telemegafone

These days, we tend to take for granted the availability of amplified sound systems. If you’re going to make a speech before a large auditorium, the first matter of business is to turn on the sound system and locate the microphone.

But there was a time, not so long ago, that electronic sound amplification didn’t exist. A hundred years ago, if you were going to be a preacher, a politician, or some other kind of public speaker, then you had to learn how to project your voice. If the people in the back row couldn’t make out your voice, then they weren’t going to hear the Gospel, they weren’t going to vote for you, or they weren’t even going to hear what you had to say. When Theodore Roosevelt gave his “big stick” speech in 1901 at the Minnesota State Fair, hundreds of people heard him because he used a big voice to deliver it.

It was only in the 20th century that public speaking came to be associated with electronic amplification. As we’ve previously reported, for example, Notre Dame cathedral was first wired for sound in 1925. And when the Iowa legislature was getting a sound system in 1939, it was probably about the same time as other legislative chambers.

One of the first examples of an electrical sound system comes from Talking Machine World a century ago this month. This particular system wouldn’t have been of much use to preachers or politicians trying to be heard in a large auditorium, but it’s an early example of what would be perfected within a few years. The Magnavox Telemegafone system shown here could be used with a phonograph, or with what we would today call a microphone, although that term hadn’t been coined.

I describe this as an “electrical” system rather than “electronic,” because there doesn’t appear to be any electronic amplification. The microphone is probably a carbon mike, and the phonograph transducer probably is as well. They drive the speaker directly. The speaker does not have a permanent magnet. Instead, it has a field coil powered by a 6 volt battery.

One of the described purposes is as a “novelty,” and a speaker who could project his voice well would probably be better off not bothering. But within just a few years, the idea of electronic sound would become popular, and the profession of “sound man” would be born. And a century later, we would take for granted that to speak before a large audience, we need to find the microphone and turn on the P.A.

1960 Two Tube AM-FM Stereo

This listener was undoubtedly the first on her block to tune in a stereophonic broadcast, thanks to the two-tube AM-FM stereo receiver shown in the July 1960 issue of Electronics Illustrated.

That’s right, With only two tubes, this radio pulls in AM-FM stereo broadcasts. If you wondering how that’s even possible, read carefully. It doesn’t receive FM stereo broadcasts. In fact, the FCC didn’t even adopt a standard for FM stereo until 1961. Just like I said, it receives AM-FM stereo broadcasts: An AM station is transmitting the left channel, the right channel of the program is being transmitted on FM. The set is actually two separate two-tube receivers. It uses a dual triode 12AT7, one half as a regenerative AM detector, and the other half as a superregenerative FM detector. The set contains two audio amplifiers, each using half of a 12AX7. A DPDT switch on the stereo headphones allows the listener to select AM, FM, or AM-FM stereo.

The author concedes that the set is basically experimental, and not high fidelity. But he added that the set gave remarkable qualities of depth and direction to the sound. By tweaking the coils a bit, the FM side could also be used to listen to TV audio when stereo broadcasts weren’t on the air. The magazine noted that stereo broadcasts would be listed in the newspaper, and were available in many cities.

In addition to being the first on her block to have a stereo receiver, this woman could very well have been one of the few on her block to have an FM receiver of any kind. They were starting to show up by 1960, especially in higher-end console radios for the home. AM-FM portables were available, but as this issue of the magazine also shows, they were very expensive. This Zenith AM-FM portable, the Royal 2000, gives every indication of being a top performer. But it also sold for the princely sum of $189.95.

A minimum wage worker earning a dollar an hour would have to work for more than a month to afford this radio, and still wouldn’t have enough money to buy the eight D cells. Putting together your own AM-FM stereo doesn’t sound like that bad a deal.

Paper Clip Motor

If you’re looking for a science fair project that can be put together with parts you’ll find around the house, you can’t go wrong with this motor from the July 1940 issue of Popular Science.

The main components used are paper clips. You’ll also need some insulated copper wire and a few other odds and ends. The old-fashioned dry cell batteries look cool, but it will work just as well with a couple of alkaline D cells.

Kathi’s CB Carousel Turns 50

We’ve previously written about (here and here) Elementary Electronics CB editor Kathi Martin, KGK3916. She got her big break fifty years ago this month, July 1970, when her column, Kathi’s CB Carousel, first appeared in the magazine.

We read her column every month, but we always wondered what a nice girl like Kathi was doing in a place like 11 meters. In any event, we congratulate Kathi on this important anniversary and wish her all the best.

One of our readers made a strong circumstantial case that Kathi, along with her husband, is the author of this interesting looking book on how live a retirement lifestyle yet keep money rolling in with continuing education seminars. It’s not a bad idea, as I also try to make a living with such seminars (although mine tend to be in places like Iowa, and she seems to recommend more popular tourist destinations).

1960 CB Converter

Sixty years ago this month, the July 1960 issue of Electronics World carried the plans for this CB converter. The magazine noted that inexpensive transceivers were available with superregenerative receivers, and that those worked well at first to get people on the air at a low price. But as the band became more and more popular, the lack of selectivity posed a problem, and a superheterodyne was becoming necessary.

This circuit used a single 6EZ8 triple triode, and would use a standard AM radio tuned to 1500 kHz as the IF stage. It circuit could also be tuned to cover any 400 KHz segment of the 10 meter band.

1920 Radio Ad

We’ve previously featured ads from Young McCombs department store in Rock Island, Illinois and its well-stocked radio department. This ad appeared a hundred years ago today in the July 15, 1920, issue of the Rock Island Argus and Daily Union.

First FM Car Radio, 1960

Sixty years ago this month, the July 1960 issue of Popular Mechanics showed this car radio from Motorola, which, according to the magazine, was the first mass-produced transitorized FM car radio. The set installed under the dash, and despite its compact size, it was completely self-contained, with its own speaker.

The radio was in response to the demands of discriminating motorists who enjoyed a more specialized programming, and the set was capable of reproducing the full range of FM audio.

1950 Four Tube Pocket Portable

The gentleman shown here is listening to one of the first pocket-sized radios, the plans for which were shown in the July 1950 issue of Popular Science.

The magazine notes that you don’t have to carry your portable radio–you can wear it. The receiver is so small that it will slip into your pocket, and you’ll hardly know you have it with you. The set was a four-tube superheterodyne that would pick up everything on the dial, thanks to four subminiature tubes.

The article did state that one needed to have “a little practice in radio building” in order to put it together. Indeed, the mechanical construction looks very challenging, trying to squeeze all of the parts into a small makeup box.

Unfortunately, the project is challenging partly because it’s unclear which tube is which. The set calls for four tubes: 2G22, 2E32, 2E42, and 2E36. Unfortunately, they’re not labeled on the schematic, and the text gives only a few hints. The 2E36 is the audio output, the tube on the far right. I think the other three, from left to right, are 2G22, 2E32, and 2E42, but I’m not positive. In any event, the tubes are taped to the sides of the IF transformers to squeeze everything into place. Of course, it probably doesn’t matter, since these tubes are probably all unobtainium.

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