1921 Homemade Phonograph

A hundred years ago, the cost of a phonograph was becoming reasonable so that most Americans could afford one. But for the frugal handyman, there was another option, as shown here in the October 1921 issue of Popular Science.

Not only could the home craftsman make his own phonograph and save some money, but the homemade version would be superior to most commercial phonographs. The majority of the machines were hand-crank phonographs, but this one was electric, relying on a motor powered either by batteries or household current.

The platter was made of a piece of brass, with another strip of brass soldered to the edge. This was driven by the motor using a friction drive made of a typewriter eraser
like the one shown here. Surprisingly, you can still buy a manual typewriter, but this style of typewriter eraser is no longer made. Like everything, however, you can find them on eBay.

The magazine explains how to construct the pickup and tone arm, which consists of a brass tube and the lid from a jelly jar. The board at the rear not only supports the tone arm, but serves as a sounding board, presumably providing room-filling audio.

One issue that is not addressed by the article is how to regulate the speed, since the motor will need to be spinning at about the right number of revolutions per minute. The relative size of the eraser and platter will, of course, provide some gearing, and there would be some room for experimentation. And with a DC motor, the voltage could be used to get the speed right. But the motor is going to have to start out at approximately the right speed, so some experimentation would be necessary for which motor to use.

As long as the craftsman got the bugs worked out, the result would be a quality phonograph, albeit not as aesthetically pleasing as the one normally found in the parlor. Students looking for an interesting science fair project can follow the instructions provided by Mr. Wizard in the video below. All you need is a pencil, a pin, a piece of construction paper, some tape, and, of course, a record that you don’t mind suffering possible damage.

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Young Soviet Nuclear Scientist, 1961

I’m not sure exactly what’s going on in this illustration, but the young comrade seems to be having a good time, even though both the tree and the bird are rather distressed.

At the top, it seems to read that the diode tube, plus “plasma”, plus “reactor” equals whatever is in the bucket that is powering the tool. So very possibly, this young man went on to a career in science, such as designing the Chernobyl nuclear plant.

Whatever it is, it appeared in the October 1961 issue of Юный техник (Young Technician).

1941 Baseball Radio

In 1941, for the sports fan who wanted to listen to the baseball game on a baseball, this All American Five was available. The ball was about nine inches in diameter, and had tuning knob on one side and volume on the other.

The radio bore the “Trophy” name, and as you can see from the handwritten notation, it came from the D.A. Pachter Company, Space 1142, Merchandise Mart, Chicago. The company had a wide selection of novelty items, some of which you can see in this 1950 catalog.

They included a matching bowling ball radio, which you can see here. A nicely preserved example of the baseball radio can be seen at this link. The photo above appeared in the October 1941 issue of Popular Mechanics.

1951 Three Tube British Receiver

The plans for this handsome three-tube set are shown in the October 1951 issue of the British Radio Constructor magazine. The set uses three 6AG5 tubes, which were said to be readily available at Government Surplus Stores. One disadvantage of the tubes was the non-variable Mu characteristics, which meant that a conventional volume control was not possible. Undaunted, the volume control is placed in line with the antenna, which could be as short as a few feet. The volume control would be rendered inoperative if the antenna coil picked up signals, so the article explained how to shield that coil.

In the circuit below, the set is for the medium wave band only. If long waves were desired, a second set of coils were used, and switched into the circuit. The band switch also had a third position to power off the set.

The circuit was designed by Peter T. Pitts, G3GYE, who died in 2020 at the age of 92.

1961 Paper Clip Radio

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Sixty years ago, this gentleman was undoubtedly one of the first on his block to own a transistor radio, thanks to the circuit described in the October 1961 issue of Popular Mechanics.

As shown below, the set was an unassuming two-transistor circuit, with a 2N170 serving as detector and 2N107 as audio amplifier. You had to decide which half of the broadcast band you wanted to tune, as the loopstick couldn’t quite tune the whole band, and the value of the capacitor depended on whether you wanted the lower half or upper half.

The set had two alligator clips, one of which served as the on-off switch. The other one was used to hook to a convenient antenna. The set was constructed on a PC board, and the parts list called for the board, the marker, and the etchant solution. The set’s gimmick was the X-shaped paper clip, which could be used to clip the set to your pocket as shown, or to serve as a bookmark while reading.

1941 Radio-Phonograph Table

The October 1941 issue of Popular Science showed how to put together this radio-phonograph stand. The phonograph was placed in a drawer, not just for aesthetics, but to improve its performance by muffling the needle scratch and motor noise.

The record player typically plugged in to the phono jack on the back of a radio, which was placed on top of the table. The bottom shelf could be used for record storage. The magazine noted that the the table could be built with a dollar’s worth of lumber, a sheet of plywood for the table top and drawer base, and white pine for the rest of the design.

1921 Signaling Device

A hundred years ago this month, the October 1921 issue of Popular Science showed this signaling device for use by the military. It provided a level of security, because its light beam was visible only over a small area. It’s a very simple idea–it consists of a telescope with a flashlight bulb mounted inside at the focal point. It was easily aimed by looking through the telescope. The bulb’s filament was visible, and it was simply a matter of lining it up so that was visible over the spot where you wanted your signal seen.

Students looking for a science fair project could easily recreate this. All that’s needed is a toy telescope like the one shown here. It can be carefully disassembled and the bulb place inside. You can use the bulb from an old flashlight, or buy the bulb separately. For this project an old-fashioned incandescent bulb will work better than an LED.

You’ll also need some hookup wire and batteries. While not absolutely necessary, a battery holder will make the job a lot easier. Normally, for a science project involving light bulbs, it’s most convenient to get a socket for the bulb. However, in this case, the socket might not fit. Therefore, the best option would be to solder the wires directly to the bulb. A soldering iron, complete with solder and everything else you need, is surprisingly inexpensive.

To send Morse code, you’ll also need a small pushbutton switch.

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Mathematics for Self Study/For the Practical Man: 1941

I find this ad intriguing on a number of levels. This particular instance is from 80 years ago this month, from the October 1941 issue of Popular Science. (You can click on either image to see a full size view of that page.)

Presumably, the publisher was able to make enough money to pay for two full pages in a national magazine by selling a five-volume set on mathematics for $8.95 over three months ($166.56 in 2021 dollars, according to this inflation calculator). Somehow, I doubt if they would have enough takers today.

The title of the series is “Mathematics for Self Study,” and it gets more curious when you consider the five individual volumes. They cover arithmetic, algebra, geometry, trigonometry, and calculus. One would think that the prospective customers for the arithmetic volume would have little overlap with the ones buying the calculus book, but here they are, offered as a package deal.

The author is James Edgar Thompson, of the Department of Mathematics of Pratt Institute in Brooklyn.

Even though it seems odd at first, there does appear to be a continuity between the books. The first volume, for example, appears to be much more than a primer on the subjects that were covered in elementary school. According to the ad, the arithmetic text starts with a quick review of principles, but then “presents all the special calculation methods used in business and industry which every practical man should know.”

The practical value of the set is stressed throughout the ad. The algebra book shows how to solve problems which are “involved in all military and industrial work.” Geometry covers all of the topics essential in drafting and engineering. Trigonometry covers the essentials for machine work, land surveying, mechanics, astronomy, and navigation. And the calculus book, “the branch of mathematics that deals with rate problems” allowed the solution of problems regarding areas such as efficiency and velocity. It noted that calculus was applied directly in the design of rifles and cannon.

The preface of the calculus volume explains the inherent continuity of the books:

In arithmetic we study numbers which retain always a fixed value (constants). The numbers studied in algebra may be constants or they may vary (variables), but in any particular problem the numbers remain constant while a calculation is being made, that is, throughout the consideration of that one problem.

There are, however, certain kinds of problems, not considered in algebra or arithmetic, in which the quantities involved, or the numbers expressing these quantities are continually changing. Many such examples could be cited; in fact, such problems form the greater part of those arising in natural phenomena and in engineering. The branch of mathematics which treats these methods is called the calculus.

I found a few modern reviews of these books, and almost without exception, the reviews are overwhelmingly positive. I’ve seen a few complete sets of the books for sale, for hundreds of dollars. However, for those wishing to acquire a set, it can be done economically. The same set of books was published over many years, and there are slight variations of the titles. The set sold in 1941 was entitled “for self study,” but later editions seem to have adopted “for the practical man” as the title. As far as I can tell, there were few changes, so Arithmetic for Self Study is probably essentially identical to “Arithmetic for the Practical Man.”

If you don’t mind a bit of variation, you should be able to find all five volumes at a reasonable price. The links below should help you find them. In many cases, the prices of different editions can vary considerably, so you’ll want to check all of the links below before placing an order.

Arithmetic

Algebra

Geometry

Trigonometry

Calculus

The set was published by the D. Van Nostrand Company, which I believe is most famous for its behemoth Van Nostrand’s Scientific Encyclopedia. Of course, if you want to read all of the books at no cost, they are available in many public libraries. You can find them at Worldcat, and your local library should be able to get them with interlibrary loan.

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1941 ARRL Battery-Powered Equipment Test

Today marks the 80th anniversary of an ARRL contest that, as far as I can tell, happened only one time, the 1941 ARRL Battery-Powered Equipment Test. The announcement shown here appeared in the September 1941 issue of QST, and the full rules appeared in the October issue.

While June Field Day was, and is, dominated by gasoline powered generators, this event was “aimed at individual-class lighter weight equipment.” To stress this, the official contest exchange included the transmitter weight. Participants could work non-contest stations for one point, with an extra point for sending and getting acknowledgment of the transmitter weight. If the other station was battery powered, there was an additional point for copying their transmitter weight.

In my opinion, the small advantage gained by an electric generator is more than offset by the convenience of operating with batteries. For example, as I previously reported, I worked the 2021 Winter Field Day contest with my trusty fish finder battery. Especially if you’re thinking in terms of emergency preparedness, it’s an easy matter to keep fully charged batteries on hand, whereas a generator usually requires a certain amount of maintenance, as well as keeping fuel on hand.

The maximum power level for the 1941 contest was set at 30 watts, although it would have been a stretch to get more from battery-powered equipment. Operation from the field was encouraged, with a multiplier of of 2 for all contacts. However, stations could also be operated from home, as long as batteries provided all power for transmitter and receiver. The contest rules reminded hams that portable operation required 48 hours advance notice to the FCC.

There were categories for both HF and VHF (called in those days “low frequency” and UHF). Interestingly, HF operation was confined to the daylight hours, but UHF could continue all night. The UHF category allowed 5 meters and up, but all of the entries in that category used exclusively the 2-1/2 meter band.

The results weren’t published until after Pearl Harbor, in the March 1942 issue of QST. They are shown below, with W8RMH, Edgar Cantelon of Detroit, later W8CV, taking the honors for high score with 82 contacts from a portable location. Among the calls is one familiar one, that of Don Wallace, W6AM, whom we have previously profiled.

In the “UHF” category, W2NPN took top honors, with an impressive 72 contacts from a portable location, all on 112 MHz.

The “transmitter weight” is an interesting piece of data to exchange. Even though this contest is no more, transmitter weight is still a factor in at least one contest. While it’s not sent on the air, transmitter weight is an important factor in scoring for the Adventure Radio Society Spartan Sprint contest. In the most recent running, K4PQC managed 11 contacts with a station (transmitter, receiver, headphones, and battery) weighing in at 0.1268 pounds (2 ounces). He reported that his station consisted of a 40 meter ATS-3b. The rig is designed to fit inside an Altoid’s tin, but he ran it without the case to shave a whopping 1.2 ounces off the station weight.

I suspect W8RMH’s rig weighed a bit more in 1941, but he probably used a lot of other gear, both larger and smaller, over the years. According to his 2016 obituary, he had just started working at WJBK radio (now WLQV) shortly after this contest, and he was in the transmitter room when the station reported that Pearl Harbor had been attacked. He then secured a new job in a defense plant, later becoming a radio operator for bomber test flights. He later served in the Merchant Marine as a radio operator, and then the army. He later went back to WJBK and served as an engineer for their TV station.

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1941 Homemade Toys

Chances are, the hot new toy that you planned on buying Junior for Christmas is stranded somewhere in a flotilla of container ships off the coast of Long Beach. Maybe they’ll break the logjam before Christmas, but as our Secretary of Transportation had to admit, we probably shouldn’t count on it.

But despite the official concessions of gloom, there’s no reason why ineptitude needs to spoil Christmas. If you get to work now, you can make toys that are far superior to the unobtainium Chinese imports. And for the younger children on your Christmas list, you can’t go wrong with these colorful animals from the October 1941 issue of Popular Science.

All you need is a band saw or jig saw, and a single piece of 3/4 inch plywood 12 by 24 inches. The plywood might be more expensive than usual this year, but it’s probably sourced in North America, and you shouldn’t have much trouble tracking it down. If you don’t already have the saw, keep in mind that they’re also waiting off the coast of California, so you’ll want to get that right away before everyone else gets the same idea.

Complete plans are found on page 178 of the magazine, which you can read at this link. Instructions are also given for the bases and storage box, as shown below. The pattern for cutting the animals is shown at left (click on the small image for the complete full-size version). You simply trace the design onto a piece of 1/2 inch graph paper and use that to cut. When you’re done, the animals should be painted in bright colors, and the magazine reminds readers to “be sure to use nonpoisonous, washable, enamel” paint.

When finished, the set will keep youngsters happily occupied for many hours. As the magazine points out, the toy teaches how to discriminate between colors, recognize the various animals, develop creative instinct, and rewards the child with a sense of accomplishment, all factors recognized as essential to proper development. Chances are, the Chinese toy doesn’t have all of these advantages.

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