Category Archives: Radio history

1943 One Tube AC-DC Shortwave Regen

The October 1943 issue of Radio Craft carried this schematic for a one-tube AC-DC shortwave receiver. The circuit had been sent in by Leo Silber of Springfield, Mass., who reported that in 25 nights, he had pulled in over 200 stations from as far away as Little America, Antarctica.

The set used a 6C8G, with half the tube serving as rectifier and the other half as regenerative detector. Plug-in coils were used along with a variable capacitor for tuning. Silber reported that the set could drive either headphones or a small speaker.

For those wishing to duplicate the circuit, it appears that a 6SC7 can be substituted. Those tubes are still rolling off the Russian assembly lines of Sovtek, and are available on Amazon. For information on winding the plug-in coils, see our plug-in coils page, and for sourcing other parts, you can get ideas at our crystal set parts page.

If the circuit looks familiar, it’s because the magazine’s March 1943 issue had carried a slight variation on the same circuit, also sent in by Mr. Silber. Silber, then a high school senior, was apparently not licensed before the War, but the 1949 call book shows him as holding W1NRP. He went on to receive his Ph.D. in Physics from Purdue University, and later served as Professor of Electrophysics at the Polytechnic Institute of New York, Brooklyn. A 1981 biography is available at this link.

1943 Cable Reel

In 1943, teen girls went for the boys on the Audio-Visual crew, as shown by this illustration from the October 1943 issue of Popular Mechanics. (Note the book bag at her feet, ready to be carried home by one or both of the helpful lads.)

The two shown here are running wire to an extension speaker using the large diameter reel shown in the magazine. Not only are they impressing the girl with their knowledge and skill, but they’re being patriotic by being careful with wartime strategic materials, since storing the cable on such a reel made it last longer than if simply hung on a nail or small diameter peg.

The boys probably made the reel in wood shop where they showed their skill, since the magazine noted that the unusual design, shown here, “provides an interesting sawing problem for students.”

1928 eCommerce Prediction

There doesn’t appear to be anything in the way of explanation inside the magazine, other than the promise of “soon” on the cover. But Hugo Gernsback seems to have anticipated Amazon with this illustration on the cover of Radio News 90 years ago this month, September 1928.

The TV seems to be selling suits, and the viewer seems to have a button in his hand, getting ready to order as soon as the one he wants appears on the screen.

1958 Portable Phonograph

The young woman shown here on the cover of the September 1958 issue of Electronics Illustrated is listening wistfully to some music courtesy of the portable phonograph she constructed according to the plans contained in that issue.

She was able to put the project together in just a few hours, and it allowed her to listen to music wherever she pleased, thanks to the fact that the set ran entirely on batteries. Both the motor (three speeds–45, 33, and 16 RPM) and the amplifier were powered by four flashlight batteries, and the completed phonograph was no larger than a small overnight bag, light enough for a child to carry.

The circuit consisted of two CK722 transistors, as well as a 2N255 mounted on a heatsink, which provided enough power to drive the speaker. Volume was said to be adequate for dancing and mood music, although the article pointed out that it was not a high fidelity instrument.

While there’s no way of knowing for sure, it’s likely that she is being entertained by a former Vice President of the United States. Topping the charts that month was “It’s All In The Game” performed by Tommy Edwards, which you can listen to in the video below.

Charles Dawes. Wikipedia image.

The melody of that song, originally unimaginatively entitled “Melody in A Major,” was composed in 1911 by Charles G. Dawes, who went on to become Vice President under Calvin Coolidge and earned the Nobel Peace Prize in 1925. Under President Hoover, Dawes served as ambassador to the United Kingdom. The song has the distinction of being the only number one single to have been composed by a Vice President of the United States. The Wikipedia entry for the song incorrectly states that the song is the only one to have been composed by a Nobel laureate, but the Dawes biography points out that this distinction is now shared with Bob Dylan. Dawes shares with Sonny Bono the distinction of being the only members of the U.S. Senate or House of Representatives to be credited with a number one hit.

In addition to being a banker, composer, diplomat, soldier, and politician, Dawes was a rather prolific author, as can be seen at his Amazon author page. A 2016 edition of his Journal of the Great War is still available.

https://www.youtube.com/watch?v=Gtizr2G_7Bk

1958 Personal Stereo & Simple TImer

Maybe it’s just our imagination, but the girl in this photo from the September 1958 issue of Popular Electronics looks just a bit disappointed. She was told that she was going to have the opportunity to listen to a personal stereo player, not long after the concept of stereophonic music had been introduced to the public, and a full four decades before the Sony Walkman hit the market and made the concept of “personal stereo player” familiar. Instead, she’s listening to the phonograph through a set of crystal set headphones, thanks to this simple project shown in the magazine.

She probably did have to admit, though, that it was a clever idea. As the magazine pointed out: “If you are anxious to try the new stereo records, there’s no need to wait until you can acquire a two-channel audio amplifier and a pair of speaker systems.” Instead, the ceramic stereo phono cartridge was hooked directly to the crystal earphones. As with a crystal set, the circuit was entirely self-powered, and didn’t require any amplification. According to the magazine, the set was useful as a demonstrator for entertaining friends or for listening without disturbing others. It also pointed out that public libraries and record stores could use a similar setup.

For listening to mono records, the circuit included a switch which put the two earphones in parallel.

This wasn’t the only extremely simple circuit included in the magazine. The issue also included the timer circuit shown below, which was said to be good for measuring 5-50 seconds, depending on the setting of R1. The timer worked by charging up the large capacitor with a 9 volt battery. After being fully charged, the capacitor discharged through the solenoid of a sensitive relay. When the capacitor discharged sufficiently, the normally-closed relay disengaged, setting off whatever alarm was desired.

Bringing the Car Radio Inside

With the family car out of service for the duration, the September 1943 issue of Popular Mechanics offers this suggestion for putting the radio and battery to work by bringing the radio into the house.

Here, the set is mounted on a small shelf, with a speaker mounted above it. The six-volt car battery is in a carrier on the floor underneath, connected to an optional trickle charger. The antenna is mounted on a bracket on the wall. The ground wire is run to a metal plate which could be placed under a carpet or, on the ground floor, to a piece of sheet metal placed under the floor joists.

The magazine points out that the car radio probably provided good reception. If the project looks familiar, we previously carried a similar one for mounting the radio inside, and another for putting the radio on a bicycle.

1938 Meissner “Remote Control”

This ad for a Meissner “remote control” appeared in Radio Retailing magazine 80 years ago this month, September 1938. It promises pushbutton tuning and volume control for any receiver.

The device appears to be a complete radio receiver of its own, which rebroadcast the desired signal at a blank spot on the dial of the radio it was controlling. The giveaway is the fact that the “remote control” is connected by 15-foot cable to the antenna and ground connection of the receiver, and that it requires its own power connection.

The remote was certainly smaller than the receiver though, since its handsome light walnut cabinet measured only 4-1/2 inches high.

1958 One Tube Regen

This radio wasn’t elegant looking, but it pulled in stations. The plans for this simple one-tube regenerative receiver appeared in the September 1958 issue of Popular Electronics. The set could tune the broadcast band and three shortwave bands, courtesy of coils switched with a bandswitch. It would provide loudspeaker volume or drive headphones.

A single 12AU7 dual triode served as regenerative detector and audio amplifier. Most parts, with the exception of the coils, should be readily obtainable. It’s likely that the coils would have to be wound at home.

The set is mounted on two pieces of masonite pegboard, providing a ready made speaker grill. The speaker is mounted on a cardboard baffle. The author reports that the set pulled in HCJB almost immediately with a short indoor antenna, after constructing the set in a single evening.

1948 One Tube CW Transmitter

This schematic was sent in to the September 1948 issue of Radio Craft (the last issue published under that name) by one Robert Fink of Cleveland, Ohio. The circuit was probably a bit on the chirpy side, and the output filtering probably isn’t adequate by modern spectral purity standards, but it probably got the job done. It put out about 20 watts on 80 or 40 using a single 1614 beam power pentode (plus a type 80 full wave rectifier.)

Tuning was accomplished by plugging an ammeter into the key socket and tuning for maximum current of 80-90 mA.

Wood Burning USB Charger

We recently featured a 1958 Soviet kerosene powered radio and lamented the fact that similar products are not available today. It turns out, however, that we were wrong.

First, a Facebook comment to our original post alerted us to the Lufo lamp, shown here. This is a kerosene lantern, apparently developed as part of a UN project to provide radio receivers for Africa. The heat from the lamp operates a Peltier effect device which powers the built-in AM FM radio.

These don’t appear to be manufactured currently, but they are reportedly available in Europe if you look hard enough.

There is, however, one device on the market currently, and it doesn’t even require kerosene! At Amazon, you can purchase a wood-powered USB charger that uses the same principle. You can then charge your phone using sticks gathered from your yard.

The USB charger appears to be a bit of an afterthought, but also appears to be fully functional. It appears that the Peltier device power supply is intended mostly to power an internal fan that increases the efficiency of the stove. But it also provides usable power, which is available from the USB socket.

The stove also includes an internal 2600 mAh lithium-ion battery to store the charge. According to the Amazon reviews, the stove itself works extremely well. According to one review, the stove will boil a pint of water in about four minutes, which is quite good for a stove burning nothing but small twigs. The stove is useful for charging a phone or other device. The fan speed appears to be a trade-off. With the fan on high speed, the stove runs most efficiently, but it also uses most of the current that is produced. It appears that the best compromise for generating electricity is to run the fan on low speed.

For the do it yourselfer, it seems that producing a similar device should be relatively easy and inexpensive. The Peltier elements are readily available on Amazon. You can also order direct from China with free shipping at this link. They’re normally intended for use in applications such as 12-volt coolers, where an electric current is run through the device, where it produces a difference in temperature between the hot side of the device and the cold side. But this is a case where the physics works the same with a minus sign in front of the equation: If you generate a difference in temperature, this will cause electric current to flow.

You’ll probably need more than one, and you’ll probably have to experiment with wiring them in series (to increase voltage) and parallel (to increase current) to get sufficient power. You’ll also need some kind of heat sink mounted on the cold side. The device will have maximum output when the temperature difference between the two sides is greatest. So you need to get one side as hot as possible while keeping the other side of the thin device as cool as possible.

Once you have sufficient voltage and current, you can hook the output to a 12 volt USB charger. Even if you don’t have a full 12 volts, most such chargers are little more than a voltage regulator, so as long as your output is more than 5 volts, you should have a fully functional USB power connection.

To use your new power supply to listen to the radio, you could add the small portable shown here. When batteries are available, you can use standard AAA batteries. During the day, you can run it with the built-in solar cell. And at night, you can plug it in to your wood burning charger with its USB port.

Of course, most of our readers will want to listen to shortwave, and will probably opt for this inexpensive USB-powered receiver which tunes AM, FM, and 4.75-21.85 MHz shortwave.

In addition to being useful for camping or emergencies, such a project would be excellent for a science fair project.

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