Category Archives: Radio history

Motorola Playmate Junior, 1947

Seventy-five years ago, these youngsters, shown on the cover of the January 1947 issue of Radio News, had been especially good, since Santa had brought them, among other gifts, this Motorola Playmate Junior portable radio (Model 51M1U).

The four-tube (1R5, 1U4, 1U5, 3S4) portable covered the broadcast band, and ran off batteries or AC. On AC, the set used a selenium rectifier.

Actress Jeanne Crain had apparently also been a good girl, since she is also shown with the same model in the ad below, which noted that the set was the company’s most compact portable and had excellent signal pickup and shock-resistant tubes. It also notes that the antenna is conveniently built in to the cover. Since the ad mentions the film “Take Care of My Little Girl,” it must have been from about 1951, meaning that the set remained in production for quite some time.

Wikimedia commons image.

Jewel Model 5050: 1951

Seventy years ago this month, the January 1951 issue of Radio Retailing carried this ad for Jewel’s combination table model/portable set, the model 5050. The ad notes that whether on a table or being carried, the dial is always in a convenient position, and the sound is always pointing in the right direction.

The set operated on household current or battery, and featured a ferrite core antenna. The set had four tubes, 1R5, 1U4, 1U5, and 3V4

1942 Code Practice Oscillator

Eighty years ago, these gentlemen probably realized that they would soon be serving in the armed forces, and their stint would probably be more comfortable if they came to their induction in possession of a skill useful to Uncle Sam. Therefore, they have undertaken to learn Morse Code, thanks to this one-tube oscillator described in the January 1942 issue of Popular Mechanics.

The set used a single 117L7-GT tube, whose 117 volt filament meant that it could run straight off the AC power lines, without worrying about dropping resistors or transformers. It had plenty of volume, which could be controlled with a volume control, to drive a speaker or up to 20 pairs of headphones for group practice.

William F. “Billy” White III, K5CBZ

Photo, Toomey j Gazette, Fall-Winter 1962.

I am not old enough to have to have worried about contracting polio, but I am old enough to have known people who suffered from the effects of polio. Amateur radio has always served as a window on the world for those with many types of disabilities, and I had the pleasure of meeting many hams who were handicapped as the result of polio.

Thanks mostly to the vaccines of the 1950s, North America saw its last case of polio in the 1970s, and children and their parents no longer had to worry about contracting it. But there were still many survivors of the disease when I was growing up in the 1960s and 1970s, and largely because I was a ham, I had the pleasure of meeting many of them.

One example was profiled in the December 1961 issue of QST, thirteen-year-old William F. “Billy” White III, K5CBZ, of Corpus Christi, Texas. White had been confined to an iron lung for eight years, and it was from that location where he spent all of his time, doing his school work, reading, and watching television. But recently, he had added to his repertoire the magic of amateur radio.

His first novice station was installed by a group of local hams, but could be operated only when he was out of the respirator, meaning that the time on the air was extremely limited. When he passed the Conditional test, a permanent solution had to be found. And thanks to the local hams, it was. It was decided that a Collins KWM-2 transceiver would be a good choice since it was relatively lightweight at 18 pounds and completely self contained. It was possible to mount the transceiver directly on the iron lung using fittings that were normally used for items such as mirrors and book holders. The set was mounted vertically, and could be removed and reinstalled in a matter of seconds.

Billy was able to operate the controls using a spatula held in his mouth. The only exceptions were the band switch and transmitter tuning. But when those were set, he could operate the set by himself.

During Hurricane Carla, Billy handled a considerable amount of emergency traffic from his station. When power at his house failed, the local hams delivered a generator, which powered both the radio and the iron lung.

Billy died in 1967 at the age of 19. But for the last six years of his life, as the article notes, “daily he traveled the airwaves, visiting friends, meeting new people, and filling his time through the magic of amateur radio.”

For people with disabilities who are interested in learning more about amateur radio and other assistive technology, we recommend you contact the Courage Kenny HandiHam Program, which has carried out that mission since 1967.

KIRO Seattle; Milton Shaw, 1917-1944

Eighty years ago today, the December 29, 1941, issue of Broadcasting showed Private Milton Shaw of Cleveland, Georgia, standing guard over the 50,000 watt transmitter of KIRO, Seattle, sited on Vashon Island. The soldier was one from the 41st Division. The magazine claimed that the station was “located in the center of a large colony of Japanese nationalists.” The magazine noted that the station was the only 50,000 watt station north of San Francisco and Salt Lake City.

According to this source, Shaw was killed in Action in New Guinea on June 17, 1944, and his remains are buried at Oakwood Cemetery, Oakwood, Georgia.

Worldwide TV: 1951

Seventy years ago this month, the December 1951 issue of Popular Mechanics carried a feature with the byline of RCA Chairman of the Board David Sarnoff discussing the prospects of international television. He predicted that before long, viewers would be able to bring exciting events from distant lands to their armchairs with a flick of the dial, all at the instant they’re taking place.

He outlined the ways this might happen, but interestingly, he fails to mention the technology that did make it happen, namely orbiting satellites.

His most promising idea is shown above, namely a network of microwave relays about 20-50 miles apart. This network was already taking shape in the US, and Sarnoff pointed out that it could easily be expanded from Patagonia to Alaska. And since it was only 40 miles acroos the Bering Strait, there was no technological reason why the network couldn’t be thus extended into Eurasia, and from there to Africa. He notes that there were plans for a telegraph land line along the same route 90 years earlier, which was abandoned only after the success of the transatlantic telegraph cable.

Another idea for connecting America and Europe was a string of artificial islands in the Atlantic, 200 miles apart, each with a 1000 foot tower.

We’ve previously mentioned the idea of stratovision, namely, using aircraft both to broadcast and relay programs. Sarnoff hinted at a possible expansion of this system to link America and Europe. He noted that there were already enough commercial flights flying the route, and that if these planes were fitted with television relays, they could provide a permanent microwave link across the Atlantic.

Science Fair Idea: Electrostatic Precipitator

Seventy-five years ago this month, this young woman undoubtedly took home the blue ribbon of the 1946 Science Fair with this experiment in which she constructed an electrostatic precipitator to fight air pollution. In the photo above, a column of smoke is rising. But the moment she flips the power switch on her precipitator, the smoke ceases. An electrostatic precipitator, known at the time as a Cottrell precipitator after its inventor Frederick Gardner Cottrell, removes particulate matter from the air through an electric charge, but does not affect the flow of gas. The same principle is used in home air purifiers such as this:

In the 1946 experiment, a column of polluted air passes through a mailing tube, where it passes through a high voltage electric field. Particulate matter clumps together as a result of the electric charge, and falls to the bottom of the tube.

We enjoy providing inspiration for projects such as these, and we hope modern school children can do the same experiments. And for this project, your young scientist will need the following items. Where available, we have provided links to Amazon:

Mailing tube
Toothpicks
Foil
Wire
Model T spark coil
Cigarette

As you see, Amazon no longer has all of the needed parts. The Model T spark coil is apparently out of production. And while this young woman had no problem bringing a pack of Chesterfields to school and nonchalantly lighting one up in the science classroom to show off her invention, it’s no longer 1946. If a kid did that today, they would probably get expelled. So if Junior wants to do this experiment today, some modification is necessary.

Fortunately, as long as your young scientist has some creativity, substitutions shouldn’t be a problem. In place of the cigarette, the original 1946 experiment allows for the use of an incense stick, and as long as Junior has the teacher’s permission, this shouldn’t be a problem.

The Model T spark coil, however, is a bit more problematic. The spark coil from a Model T was known as a trembler coil. The device was a transformer. To be able to operate with DC, the coil operated in interrupter: When voltage was applied to the coil, the magnetic field opened the contacts of the interrupter, which turned off the coil. With the coil off, the contacts closed, allowing the coil to re-energize. The result of this on-off action was an alternating current, and the voltage of this alternating current was stepped up to thousands of volts with the transformer.

The Model T spark coil remained in production for many years after the last Model T rolled off the assembly line, and many of them found their way into things other than cars. When this experiment was published in Popular Science in December 1946, there was apparently no question that if you wanted a Model T spark coil, that finding one wouldn’t be a problem. One popular use of the coil in the early days of radio was for use in a spark-gap transmitter.

But if you walk in to the parts counter of your local Ford dealer today, they probably don’t have them any more. (On the other hand, there are still Model T’s on the road, and if you want to buy a new spark coil, they are still being made, but they’re probably too expensive, such as this one.)

The advanced student should be able to build their own induction coil. They will need a transformer and a method of interrupting the current. Experimentation with a filament transformer and mechanical buzzer will probably prove fruitful. Our earlier post describing a spark coil should give the advanced student enough information to construct one that is essentially identical to the Model T version.

The school might already have the equivalent stashed away in the back room of the science lab, or you could convince the teacher to spend some of the science budget on one of these:

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1951 Raytheon Model RC-1720 Starlight

Shown here from 70 years ago is an ad for Raytheon Television’s deluxe offering, the model RC-1720 “Starlight” set. According to the ad, the set was famous for fringe area performance, and it boasted a 17 inch picture tube, along with room-filling volume from a 10 inch speaker.

The set retailed for $369.95, which was down from the previous price of $469.95. That price included the federal excise tax, as well as a one year warranty. In addition to the TV, the set included an AM radio (but no FM), and a three speed phonograph.

In 2021 dollars, the price of the set works out to almost $4000, according to this inflation calculator. The ad appeared in the December 1951 issue of Radio & Television Retailing.

1946 Modern Crystal Set

The plans for this “modern crystal set” appeared in the December 1946 issue of Radio Craft, having been sent in by one W.J.E. Spain of Toronto. The author reported that the set was both selective and sensitive. He had six local stations in his area, ranging from 1000 to 50,000 watts, including a police station, and could pull in all of them with no interference between stations. All had good volume on headphones, and four stations were strong enough to operate a horn type speaker, with a 75 foot antenna.

At night, WLW Cincinnati and WENR Chicago came in like strong locals. The Buffalo stations were also heard regularly at night.

The switch marked S/B was used for selectivity. In the S position, the set was very selective, and in the B position, tuning was broad. He tuned with the switch in the B position, and then switched to S to cut out interference. Tuning was accomplished with S1 and the variable condensers, one of which was used for fine tuning.

The crystal was a 1N23, a germanium crystal which had been used as mixers in radars. They appear to be available today, or other diodes such a 1N34 would probably provide good results. For ideas on sourcing parts, see our crystal set parts page.

Home Study Courses Courtesy of Uncle Sam

The December 1970 issue of Popular Electronics provides some good advice to anyone seeking to learn about any subject. They were talking about electronics, but the same general advice applies to any field.

The magazine began by noting that money spent on a formal education is a generally wise investment. But in many cases, the student might not want to commit to a formal education. Among other things, formal education normally costs money.

But even though it has built-in disadvantages, a course of informal “go-it-alone” self study can provide a firm understanding, at a minimal investment. In 1970, the monetary investment came to $18.55. But in the internet age, that cost is essentially zero.

The magazine warned of simply buying a book and hoping that it would provide the correct study material, since it might not provide a broad enough scope. But the magazine noted that there were inexpensive books that were well designed for the purpose, namely, training manuals used by the military, and for sale at a nominal cost by the Government Printing Office. It went on to list those books recommended for a basic course in electronics, and the total cost was only $18.55.

Today, most of those same books are available at no cost on the internet. Specifically, here they are, with links to Google Books or other sources:

Of course, these texts are all now more than a half century old. But the basic theory is unchanged, and that course of study would provide an excellent background, even though the student might learn a bit of archaic material in the process. With minimal research, the interested student could update the course materials and include modern texts in electronics–or modern texts in any other subjects.

Today, it is quite possible to get a good university education and spend hundreds of thousands of dollars in the process. If you do this, two things will happen. First, you will presumably become a smarter person, because you have learned the material that was taught. And you will also get a handsome piece of paper from a prestigious institution attesting to the fact that you have learned the material. That piece of paper is very good to have. Indeed, if you want to do some things, such as perform surgery, then having that piece of paper is absolutely required.

But you can gain all of the knowledge without the piece of paper. Even though I have an advanced degree, I’ve come to the conclusion that for many, the piece of paper isn’t particularly valuable, even though the knowledge is.

If you pay tuition at a university, you will take courses, and during those courses, you will be given a list of books to read, and you will attend lectures explaining those texts. The books have always been available for purchase, or you can read them at the library. And in many cases, the lecture is available online for anyone to view, whether or not they have paid tuition.

If you pay tuition, you also have the privilege of showing up at the professor’s office hours and asking questions. But in my experience, students never do that.

In short, my advice to many students is that perhaps paying tuition isn’t really in your best interest any more. You can gain the knowledge for free. At that point, you’ll need to figure out a substitute for the piece of paper attesting to your knowledge.

In 1970, one suggestion that Popular Electronics made was to obtain your FCC Radiotelephone License, preferably the prestigious first class license. That option is still available, although it’s less prestigious, and the license is now called the General Radiotelphone Operator License (GROL). In fact, I’m the author of a study guide to earn that license.

The GROL is still the ticket to a handful of jobs in electronics, but in many cases, it’s unknown to employers. But there are probably other methods of proving your bona fides. And before long, other people like me, who have advanced degrees and a stake in higher education, are also going to start coming to the realization that maybe that fancy piece of paper is overpriced. And eventually, someone is going to come up with a less expensive alternative piece of paper. In many industries, that piece of paper probably already exists.

In short, my advice is to consider whether self-study might work for you. If done right, you can learn almost as much, or as much, as students undergoing formal education. And if you’re smart enough to do that, perhaps you are also smart enough to figure out a way to prove it, even without that handsome, but expensive, piece of paper.