Monthly Archives: September 2018

1938 One Tube 6L6 Transmitter

Eighty years ago this month, the September 1938 issue of Radio News carried the plans for this one-tube CW transmitter using a single 6L6. It had a power output of twenty watts, which the magazine said meant a range of a thousand miles, with the chance of greater DX.

The coil was homemade, wound on a form made by wrapping a small sheet of celluloid, siad to be available at a “harness or luggage repair shop.”

THe crystal would set the builder back about five dollars, making it the most expensive item in the transmitter. But the magazine noted that a good crystal which oscillates strongly and will follow keying is an excellent investment. The recommended antenna was an end-fed half-wave wire.

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.

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.

1943 Opaque Projector

During my school days in the 1960s and 1970s, the teacher would occasionally wheel out a monstrosity known as the opaque projector. It would project the image of an opaque object, such as the page of a book, onto a screen. Apparently, the models of that era had about a 1000 watt lamp inside, and their size was due in part to the fact that they required a big fan to keep it cool. The process also required a lens that was quite large.

The projector was rarely used. Instead, it was much more common to copy the desired image onto a transparency, which was projected with the much more common overhead projector.

75 years ago this month, the September 1943 issue of Popular Science showed how to make an opaque projector. The article doesn’t seem to specify the wattage of the bulbs, but since ordinary household bulbs are shown, I assume that they would be 100 watts. The lens is made from one, or preferably two, magnifying glasses mounted in a tube.

The opaque projector has been more or less replaced by the document camera, such as the one shown here on Amazon, which can be viewed through the video projector that is now found in almost all American classrooms.

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.

Another Flashlight Saves the Day

Seventy five years ago this month, the September 1938 issue of Popular Mechanics carried this Eveready ad with another harrowing tale with a happy ending, thanks to a flashlight with fresh batteries.

The ad recounts the tale of Mr. & Mrs. James Sponston of Cheshire, England. Night after night, the couple would hear the German bombers headed toward Liverpool. But one night, as they were preparing to retire for the evening, the elderly couple heard the sirens begin to shriek.

Mr. Spronston grabbed his flashlight, and they hurried downstairs to black out the windows. Then one explosion, and then another, shook the house. The house was half demolished, and the stunned occupants were thrown to the floor. Fortunately, Mr. Spronston remembered the faithful flashlight in his hand and began waving it. Two passing air wardens saw it and quickly directed the rescue.

Since the story was from England, there was no claim that Eveready batteries were involved. But still, American readers were encouraged to make sure their flashlights were loaded with fresh Eveready batteries. The ad cautioned, however, that you shouldn’t blame your dealer if you can’t get genuine Eveready batteries. The Army, Navy, and Lend-Lease had priority, and only a few were left for civilians. To conserve critical war materials, readers were cautioned to use the flashlight normally as little as possible. In particular, it advised making a habit of flashing it intermittently rather than continuously.

Toasters for Camping and Emergency Preparedness

Another Atlantic hurricane serves as a reminder of the need for emergency preparedness. Any number of emergencies can cause the power to go out, and if that happens, you’ll want your life to be as comfortable as possible.

Each year during hurricane season, our web page on making coffee without electricity gets lots of traffic. And there’s another electric appliance that people take for granted: The toaster.

The lack of electric power doesn’t mean that you have to give up making toast, since there’s an extremely inexpensive camping toaster available. I assumed that everybody knew about these, but the existence of this product often comes as a surprise. So whether it’s for camping trips or emergency preparedness, you might consider investing just a few dollars for one of these devices.

This toaster is nothing more than a metal plate that sits on any source of heat. You can use it on the stove at home or a camp stove. You can also use it on a charcoal grill or campfire. As long as you have a source of heat, you can make toast. Four wires fold into a frame, and you lean up to four slices of bread against the wire.

This kind of toaster only does one side of the bread at a time, so you will have to flip the bread halfway through the toasting process. But other than that minor inconvenience, the result is toast identical to what comes out of your normal electric toaster.

In addition to making toast, this toaster will cook anything that goes in your electric toaster. So it’s also good for things like Pop-Tarts, bagels, and English muffins. Other foods such as Toaster Strudels and Toaster Scrambles don’t need to remain frozen, and can be stored in a cooler for a few days. Therefore, with a camp toaster, these can be used for a very convenient hot breakfast.

Here are some of the available camp toasters on Amazon:

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