Author Archives: clem.law@usa.net

1966 Homemade Headphones

If you need a pair of headphones today, you can run down to the dollar store and find some that are quite adequate. Or you can go to Amazon, such as this link of headphones with free shipping, sorted by price.

But sixty years ago, they could be rather pricey. Fortunately, the April 1966 issue of Radio-Television Experimenter showed you how to make a set yourself. The idea is pretty self-explanatory. You started with a couple of two-inch speakers, and the remaining components could be found at a variety of locations. You needed some wire coat hangers, some small plastic enclosures, some padding, and a little bit of ingenuity, and you would be the first on your block with a pair of stereo headphones.

The total cost was said to be $4, and the project would take about three hours.



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1956 Shortwave Converter

Seventy years ago this month, the April 1956 issue of Popular Electronics showed this extremely simple shortwave converter. It consisted of little more than a diode and tuned circuit, and the output went to the antenna terminals of an AM radio, or looped around the coil. (The loop antenna would pick up too many broadcast stations, so the author recommended replacing it with a small loopstick.)

The author doesn’t explain how it works, and I don’t know either, other than perhaps by brute force on strong signals. But according to the author, he was able to pick up foreign broadcast stations and amateurs on 40 and 80 meters. Even though it appeared in the April issue, I’m inclined to believe that it worked through brute force. We previously covered a similar idea for making prewar FM radios pick up signals on the new FM band.



1941 “Powerless” Keying Monitor

Eighty-five years ago, the April 1941 issue of QST included this hint (or perhaps it was a kink) sent in to the magazine by C. Ray Wagner, W2FEN, for a “powerless” (other than filament) keying monitor. It uses a 117L7GT tube, half of which is a simple audio oscillator.  The rectifier half of the tube is powered by a pickup from the transmitter, and this RF is rectified to supply the B+ for the oscillator.  The result is that when the circuit is powered up (in other words, when there’s RF coming from the transmitter), the oscillator puts out a side tone.



1946 British Homemade Canoe

Eighty years ago this month, the April 1946 issue of Practical Mechanics showed how to build this 8-foot canoe, described as a “serviceable craft for young people.” Canvas-covered boats were apparently more common in this size, but the magazine noted that the framework required sound knowledge and woodwork experience, and not everyone was up to the job. This craft, on the other hand, was made of all wood, and was recommended for boys 12-14.

It was built with watertight compartments fore and aft, so there was no likelihood of it sinking should it capsize. But just to be safe, we recommend wearing an approved life vest.

The boat had a flat bottom, making it suitable for shallow waters. Most of the lumber was 7/8 inch thickness, and was described as shelving. A coat of creosote, and then paint, rendered the vessel waterproof. The magazine noted that the completed boat might be somewhat awkward to move around on land. It suggested temporarily affixing tram wheels and axle to the stern.

In most states in the U.S., a vessel thus constructed does not require registration. For example, in Minnesota, no registration is required if the craft is less than ten feet. You are required to have aboard the aforementioned life vest, and we recommend that you wear it. Interestingly, in Minnesota (and probably most other states), you are required to have aboard a whistle or other noisemaker, as well as a flashlight.  The article explains how you can make your own paddles, but at Amazon, you can find these nifty telescoping paddles.



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1966 VLF Receiver

Sixty years ago this month, the March 1966 issue of Electronics Illustrated showed how to build this 3-tube TRF regenerative receiver for 10-30 kHz VLF, as well as the loop antenna. The magazine pointed out that two categories of stations could be heard. The first was time-frequency standard stations such as WWVL. It noted that reception was more stable, since the ionosphere was not involved. The second category was CW stations such as NAA, on 17.8 kHz from Cutler, Maine, transmitting to submarines in most of the world from the world’s most powerful transmitter. Some of the other possible catches are shown on the chart below.

Calibration could be accomplished with an audio signal generator. Since the signal generator probably wouldn’t go all the way up to 30 kHz, the magazine recommended using the second harmonic of a lower frequency to calibrate the top of the dial.



1956 One Tube Transmitter

Seventy years ago, the March 1956 issue of Popular Electronics showed how to build this compact transmitter for the 40 meter band. It was housed in a sandwich box, available at the local dime store. The author, Elton Stolberg, W7OUV, did warn that the container was fragile when it came to drilling the required holes.  A single 6AQ5 served as a crystal oscillator, with about 16 watts input power.  Pin jacks were used for the coil socket, and cut-off finishing nails were used on the coil itself for the plug.  The transmitter was designed for 40 meters, but extra room for an 80-meter coil was included.

The author reported that he had used the radio, with a vibrator power supply, on Field Day, resulting in 53 contacts with seven states, plus Hawaii.  Sure enough, the accomplishment is documented in the Field Day results in QST for December 1955, where the grainy photo of his station, the miniature transmitter and an ARC-5 receiver, are shown.

 



1926 Closeout Bargains

If you were in the market for radio supplies (or auto parts or electric appliances) a hundred years ago, then Milwaukee was the place to be, as evidenced by this ad in the Milwaukee Leader, March 27, 1926. Times Square Radio & Auto Supply Co. (corner of Wells and Second Streets) was having a closeout, and was selling at sacrifice prices. Even the fixtures were for sale, and the building was up for rent, as shown in this ad from the Milwaukee Leader, March 27, 1926.

You could take home a Timesco 5-tube radio (complete with genuine RCA tubes, batteries, speaker, antenna and ground) for only $47.50. Many other accessories were also available.

And if you needed an electric iron, coffee percolator, toaster, or waffle iron, you could also get those at great prices. Interestingly, it looks like at least the coffee pot seems to come with the adapter, so that you can plug it in either to a two-prong outlet, or screw it directly into a lamp socket. Those little adapters can often come in handy, and you can still find them today at Amazon.



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Life Imitates Art: 1966 Personal Stereo

Sixty years ago, this cartoon looked pretty far fetched–someone walking around with a personal stereo system, oblivious to the outside world. But it was only 13 years later that the Sony Walkman took the world by storm.  And even before that, in the 1970’s, more clunky headphone radios (usually not stereo, but often AM-FM), that looked a lot like the ones here, hit the market.

OF course today, it’s basically taken for granted that if you want to listen to music wherever you are, the device to provide it is in your pocket.

The cartoon appeared sixty years ago in the February-March 1966 issue of Radio-TV Experimenter.



1941 British Four-Tube Portable

Eighty-five years ago, Britain was at war, but that didn’t stop the March 1941 issue of Popular Wireless from carrying instructions for building this 4-tube superheterodyne portable receiver, comparable with commercial sets. The “all dry” designation refers to the battery, which was a dry battery. A single “Type H” battery was used, as it contained one tap for the 1.4 volt filaments, as well as a higher voltage for the B+.

The construction article was to continue in the next month’s issue.



1941 British Wind Generator

Eighty-five years ago, the March 1941 issue of Practical Mechanics showed how to build a wind generator.  It used a propellor left over from the last war, and the axle from a Peugeot.  But with some ingenuity, it was made into a working unit.  The windmill managed 180 RPM, and since most car alternators required 1200 RPM, a 7:1 gear ratio was required.

I think of wind generators as an American phenomenon, since any respectable farm in the last century sported a windmill.  But the wind also blows in Britain, and was capable of being harnessed.

These days, wind generators such as this 1200 watt model are available on Amazon at a surprisingly low price.  Looking at the reviews, this particular one looks like a very good value, although one reviewer points out that the instruction manual is somewhat incomplete.  Our readers, of course, don’t need instruction manuals.  Also, a couple of parts needed some modification to properly mount it, but we have faith that our readers can deal with that issue as well.

Britain was at war when this article was written.  And this article serves as a reminder that wind power might play a role for some in providing electrical power in an emergency.



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