Monthly Archives: March 2022

90 Year Old Radio Fan: 1922

In 1832, Andrew Jackson was re-elected President of the United States. It would be twelve years before Morse would demonstrate his electric telegraph between Baltimore and Washington. Slavery still existed in half of the United States, and would for more than thirty years. Abraham Lincoln wasn’t yet a lawyer, but held a bartending license and was about to make an unsuccessful bid for the Illinois General Assembly. Communications with other towns took days, if not weeks. In short, it was a long time ago. But people born that year would listen to the radio in their lifetime. But people born that year would listen to the radio in their lifetime.

But a lot was about to change. The news clipping above appeared in the Wilmington Daily Commercial.

Mrs. Sarah Frederick of Turtle Creek, Pennsylvania, was an avid radio listener. The paper noted that she was an avid listener to the radio chapel services from KDKA, and that she had recently celebrated her 90th birthday. She was totally blind but had frequently expressed her wonder and delight at this product of modern science.

And she was born in 1832.

1982 Grocery Prices

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For a snapshot of grocery prices 40 years ago today, this ad for Giant Eagle supermarkets appeared in the Pittsburgh Press on March 30, 1982. Easter was right around the corner, so ham was prominently featured. Depending on brand, they started at 74 cents a pound. For comparison, according to this online inflation calculator, one dollar in 1982 was the equivalent of $2.94 in 2022 dollars. So to get a fair picture, in round numbers, you need to multiply these prices by 3. So a dozen eggs at 56 cents are about the same as $1.50 today. Coke was 99 cents for a 2 liter bottle, the equivalent of almost $3 today.

If you have trouble reading the fine print in the PDF here, you can follow this link to go directly to the ad.

1962 Metal Detector

Sixty years ago this month, the March 1962 issue of Electronics World showed how to put together this five transistor metal detector, using either 2N188A or 2N524 transistors. While these PNP germanium transistors are probably no longer manufactured, there are New Old Stock (NOS) specimens still to be found. However, the circuit is quite common in cheap metal detectors, and it’s probably most cost effective just to buy one from one of the links below.

If you’re looking for a very basic kit to build, the final link below is a one-transistor oscillator, which you use in conjunction with an AM radio for a rudimentary metal detector.

This type of metal detector is often sold as a toy, and the kids soon lose interest, or the parents confiscate it because of the annoying squeal. But they can actually work quite will, with just a bit of patience and practice.

This beat-frequency circuit consists of two identical oscillators, both tuned to the same frequency of about 100 kHz. One of them uses a coil mounted inside the case, and the other uses the search coil. When a metallic object comes near the search coil, that oscillator changes frequency. You start by tuning both to the same frequency, meaning that they become “zero beat,” and no sound comes out of the speaker. But when one oscillator changes frequency, and audio tone is heard, its frequency being the difference between the two oscillators. As long as you tune it carefully to zero beat, this type of detector is very sensitive. They’re regarded as toys because most kids don’t bother with the careful tuning part.

The secret of using this type of metal detector is to practice. Toss some metallic objects on the floor, set the unit so that the tone just barely disappears, and then see how it reacts to those objects. You’ll normally find that occasional re-tuning is necessary as the batteries get lower.

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Future of Wireless: 1947

Seventy-five years ago this month, the March 1947 issue of Boys’ Life offered scouts some predictions about what wireless communications might look like in the future. The words “handi-talkie” and “walkie-talkie” had entered the lexicon, thanks to military use of portable transceivers, and the magazine predicted that civilians would soon be enjoying their widespread use.

It starts by noting how a radio-equipped newspaper reporter could easily scoop the other papers, but the equipment was getting lighter, smaller, cheaper, and simpler, and the magazine predicted that use would be widespread.

The FCC had already authorized the citizens’ radio service on UHF, and the magazine noted that the FCC had allocated a full “10,000 kilocycles” of spectrum to the service.

The magazine hinted that a link to the telephone network wasn’t far off, and you would soon be able to “make, or receive, phone calls from your family car as you drive along.” You could even call another car!

The magazine did get some things right:

As the things come into common use, there will be a field day for cartoonists and gag writers. All kinds of funny new situations will arise when all of us begin to walk around, carrying on phone conversations as we go.

But, funny or not, the day is bound to come. As someone once remarked, ‘the world do move.’

And they got one more thing mostly right:

Taking one hand off the wheel might constitute a traffic hazard, so there is room for improvement in the equipment. Perhaps our engineers will soon be able to give us a radio telephone that works like a radio microphone and loud speaker. Then the motorist would be able to carry on his conversation simply by touching a button with his left foot, leaving both hands on the wheel. Automatic transmissions are foot eliminating clutches anyway, so the driver’s left foot will be free to take on a new job beside that of just dimming the lights.

Science Fair Idea: Re-orienting Your Globe

Fifty years ago this month, the March 1972 issue of Elementary Electronics showed this idea to improve the utility of the globe in your radio room. Normally, the globe is mounted so that it spins just like the Earth–along its axis. But you’re not required to spin the globe, and it becomes more useful if you orient it so that it can turn along an axis through your location and your antipode–the point furthest away from you. If you’re in North America, that would be somewhere in the Indian Ocean.

The advantage of doing this is that it quickly lets you see the direction and distance to any other point. The thing holding the globe in place (known as the semi-meridian) is usually marked in degrees. But you can tape a scale in miles to it, and if you rotate any point on the globe toward that line, you’ll instantly see the number of miles.

All you need to do is remove the globe from its mounting, which is usually just a matter of slipping it out. You then drill a new hole at your location and at the opposite side, and remount it.

The student desiring to bring home the blue ribbon at the science fair will quickly realize that this simple project will answer the question of “how to convert a globe into a distance measuring instrument.”

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Dan Gibson Parabolic Microphone

Shown here is Canadian wildlife photographer Dan Gibson using the parabolic microphone he developed. Here, he has the mike mounted on the prow of his canoe, which allows him to silently paddle up in search of wildlife.

This photo is from the March 1972 issue of Popular Mechanics, in which he is described as a photographer who developed the tool primarily to capture photographs of wildlife. The article hinted, however, that the system could be used to capture wildlife sounds on tape. Thanks to this microphone, Gibson became more famous as a recording artist, with his Solitudes series of recordings of nature sounds and music. Here, for example, is his recording of La Mer (Beyond the Sea):

You can find the label’s recordings on Amazon, or find more information at their facebook page. If you’re looking for a parabolic microphone, here are some of the current offerings:

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Radio Repairmen: Carrying the Whole Load

Eighty years ago, the radio servicemen of America were rolling up their sleeves, because as of April 22, 1942, as we’ve previously reported, they would carry the whole load of making sure Americans had access to the vital information and entertainment provided by their radios. Just as before, they would have to keep doing minor repairs. But in the past, there had been some sets that were so far gone that they would just be thrown away and replaced.

But the last new radio would roll off the assembly lines on April 22, so throwing away an old set was no longer an option. Many of the sets needing repairs would be older, so this ad encouraged dealers to order a full set of Rider manuals, which consisted of schematics and service data for virtually every radio built in the USA.

The ad appeared in the March 1942 issue of Service magazine.

1952 Radio-Intercom

Traditionally, the March issue of Popular Mechanics carried a radio project dubbed the “Little Giant,” a project aimed at advancing students who could make something serving a useful purpose. The March 1952 issue carried on the tradition with the set shown here. It was the customary five-tube superheterodyne, but it also included an intercom.

The magazine noted that a good radio combined with an intercom was an instrument of pleasure as well as utility. It could allow you to listen to the radio in two places, or it could be used as a monitor to send programs to or listen in to the kids in the nursery.

All of the controls were on the master station. The remote consisted of just a speaker, which also doubled as the microphone.

1942 Blackout Advice

Eighty years ago this month, the March 1942 issue of Popular Science carried a number of pointers on preparing for wartime blackouts. The magazine first noted that deciding whether or not to participate wasn’t a merely personal decision: If you didn’t follow the blackout instructions, then both you and your neighbors would be put at risk.

The good news was that it was very unlikely that large sections of the country would be subject to blackout. Therefore, it advised against running out and buying the necessary materials: You might wind up with a bunch of stuff that you don’t need, and even worse, you could cause shortages in areas where they were needed. So the key advice was to wait for official advice from civil defense authorities, and follow their instructions. In the meantime, you could read up to be prepared for that time, such as with the hints shown above. In addition, the magazine contained numerous ideas for blacking out various kinds of windows and doors. One key piece of advice was to remove bulbs from unused sockets, especially outdoors. No matter how well you were blacked out, an accidentally flipped light switch could make it all for naught for you and your neighbors.

When civil defense authorities gave you the instructions to prepare for blackout, you would be ready.

1942 Two Tube Regen

Eighty years ago this month, the March 1942 issue of Radio Craft carried the plans for this two-tube shortwave regenerative receiver. Thanks to the use of dual 1JG6 triodes, the set had four-tube performance. One half of the first tube was an untuned amplifier, which prevented the regenerative detector from radiating and messing with other sets in the neighborhood. The regeneration was controlled with a variable capacitor, and the second tube provided two stages of audio amplification.

With four plug-in coils, the set covered 145 through 10 meters. The compact size made the set ideal for portable operation.

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