In theory, nothing could go wrong using this simple crystal set from 60 years ago, from the February 1956 issue of Popular Electronics.  As the photo makes obvious, it’s a simple crystal set that uses the house wiring as an antenna.  It has no tuned circuit, so it simply pulls in the strongest local station.

The circuit is isolated from the line by a .01 uF disc capacitor. A disc ceramic rarely fails, but one failure mode is a dead short. The article warns “do not omit the blocking capacitor under any circumstances.” It also points out that all of the internal wiring should be taped over or covered with spaghetti tubing. Only one blade of the plug is used, so presumably, even if the capacitor shorts out, there’s no immediate risk of electrocution.

But just to be on the safe side, the article also warns that you should “observe the same precautions in using this crystal receiver as when using the common a.c./d.c. household table radio. Don’t hold it while standing on damp basement floors, handling water faucets or gas stoves, or when taking a bath.”

Of course, if you’re using this set in an emergency when the power is out, I guess you’re OK.  But you still want to observe all of these precautions, because eventually the power will be back on.

Seventy-five years ago today, this high-quality radio-phono was under a hundred dollars (with trade in of your old radio), at Gimbles Department Store in Milwaukee. This add appeared in the January 31, 1941, edition of the Milwaukee Sentinel.

The set came in a deluxe mahogany cabinet, and featured world-wide reception (presumably meaning that it tuned both standard broadcast and shortwave).  The automatic record changer would accomodate up to fourteen records.  It also had a “built-in antenna and ground.”

75 years ago this month, the January 1941 issue of QST contained the plans for two one-tube transmitters, both using the recently introduced 117L7GT tube. The tube was ideal for a simple transmitter, since the filament ran directly off line current, and the envelope contained a rectifier and beam-power tetrode. Thus, the set could operate directly off line current, with no transformer required. The set shown above was made by R.T. Lawrence, W8LCO, of Dayton, Ohio. The schematic below is the similar set made by Keith Hayes, W9ZGD, of Milwaukee, Wisconsin.

Either set could be easily reproduced, with minimal part substitutions, from readily available components.  It should be noted that neither of these transmitters has much in the way of output filtering, so it would probably be necessary to add an output filter to comply with modern regulations.

In his article, W9ZGD reports what many modern QRP’ers have rediscovered:

Although 4 or 5 watts doesn’t sound like much input, it is surprising what one of these little transmitters will do, particularly to one who has never tried anything like it before. Possibley, according to tradition, I should list the stations worked but, since the antenna, receiver and operating ability affect the statistics as much as the transmitter power, I’ll just mention the fact that 5 watts give a signal about one “S” point lower than 20 watts and 2 “S” points lower than 80 watts. And, anyway, it’s more fun to fish with barbless hooks!

The W8LCO QSL card shown here is from the builder of the transmitter shown at the top of the page. The QSL was for a contact a few years earlier, in which he reports running 24 watts input.

Fifty years ago, you would probably be the only one on your block with a computer if you built one of these. The January 1966 issue of Electronics Illustrated contains the plans for building this analog computer, suitable for addition, subtraction, multiplication, division, squares, and square roots.

Each dial is calibrated from 0-10, and there is a small ammeter.  For an addition problem, you set the switch to +/-, and adjust the two left knobs to show the numbers you want to add.  Then, you adjust the right knob until the meter is at zero.  Subtraction problems are done in the same fashion, except you set the right knob to the larger number, the middle knob to the smaller number, and the answer is shown on the left knob when the meter reads zero.  A similar procedure is used to do multiplication and division.  In the image shown above, the computer confirms that 5 times 4 does indeed equal 20.

For squares and square roots, a second section of one of the dual potentiometers is used so that both have the same resistance.  That dial shows a number, and the dial on the right shows its square.

The article points out that the device is basically the electronic equivalent of a slide rule (and probably much less accurate).  And like with a slide rule, you were on your own when it came to figuring out where the decimal point went.

I do remember in the elementary school library a book showing a similar contraption, which was wired up only for addition.  Instead of having three potentiometers and a meter used only for zeroing, it had two potentiometers and a meter from which the answer was read.  Despite thinking about how much easier that would make my math homework, that setup was probably much less accurate than the one shown here.

Shown here are simplified schematics showing the circuit used for addition and multiplication.  The combined wiring diagram showing the switches is, of course, also included in the article.  But the simplified diagrams give a good idea of how the thing works.  Both merely take advantage of Ohm’s law.  R1 and R2 are one tenth the value of R3.  As might be guessed, the parts list calls for linear tapered potentiometers.

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True to our name here at OneTubeRadio.com, we frequently feature one tube radios.  And more often than not, they are regenerative receivers.  The regenerative receiver was popular in the early days of radio because it could deliver so much performance out of a simple circuit.  The single tube, in addition to serving as the detector, had some of its output fed back into the tube to amplify.  If there was too much feedback, the receiver would break into oscillation, which would result in a squealing sound from the headphones, as well as those of other nearby receivers.  The anti-squeal campaign featured in an earlier post showed how this could be the bane of other local listeners.  But this oscillation also allowed the reception of CW (and later SSB) signals by simple receivers.

As far as I can tell, the regenerative receiver was first introduced to the public a hundred years ago this month in an article in the January 1916 issue of Electrical Experimenter.

An article by Frank J. Collins entitled “Regenerating Audion Circuits for Wireless Receiving” includes the circuit diagram shown above. If the circuit looks familiar, it’s because it’s the same circuit, with minor variations, used in most of the one tube radios shown on this site.

The details given in the article are for the construction of a longwave version of the set. “As most of the high-power transatlantic and transpacific stations use wave lengths of from 5000 to 10,000 meters [30 to 60 kHz], dimensions are given to cover these wave lengths only.” The author reports that with an aerial 500 feet long at least 10 feet above ground, reception of strong stations 2000-4000 miles away was possible, day or night, but that the set would work well with an antenna of 100 feet.

Drawing from Armstrong patent.

While this seems to be the first popular construction article showing how to make a regenerative receiver, it was a couple of years old by the time this article was written. It was invented by Edwin Armstrong in 1912 and patented in 1914 (US Patent 1113149).

The article warns that “while the coils described herein may be constructed by experimenters, they are not permitted to sell them to others for the purposes described, as the invention is patented.”

The author concludes by noting that “this type of apparatus and connections are well worth constructing and using, as it constitutes the most advanced means known at the present time in the reception of both damped and undamped radio signals.”

Because of the relative simplicity of the circuit, a regenerative receiver is an ideal project even today.  I have featured numerous examples in this site, most of which can be easily constructed using the vintage plans, although some parts require a bit of creativity to replace with modern equivalents.  Sets designed for the AM broadcast band will give immediate gratification, since there’s guaranteed to be something that can be tuned in immediately after making the last connection.  Shortwave sets are surprisingly good performers, and will pull in signals from around the world with little difficulty.

For those wishing to bypass the parts procurement process, a number of good kits are available.  For example, the kit shown in the illustration here is available at Amazon at a reasonable price. It’s a two-tube set that tunes both standard AM and shortwave.  For those who don’t mind substituting modern transistors for the tubes, QRPkits.com puts out an excellent kit, the Scout Regen Receiver, It tunes only shortwave, but covers enough territory to almost ensure that you’ll be able to tune in something interesting, day or night.  At night, the dial will be packed with amateur, commercial, and shortwave broadcast signals from around the world.

My son and I put together the Scout Regen a few years ago, and it is an excellent performer for such a simple design.  One that appears to have similar performance, but probably a bit easier to put together because of its wide-open layout, is the Ozark Patrol receiver designed by David Cripe, NM0S and distributed by the Four State QRP Group.  If you build any of these, you’ll have a very sensitive receiver capable of pulling in many interesting signals, and you’ll also be working with the same circuit employed by experimenters a century ago.

This photograph of the Boswell Sisters appeared 85 years ago in the January 1931 issue of What’s On The Air magazine.  They were then appearing on NBC’s Camel Pleasure Hour originating in San Francisco.

The sisters Martha (1905-58), Connie (later spelled Connee, 1907-76) and Helvetia “Vet” (1911-88) grew up in New Orleans where they studied classical music, but their mother also made sure that they were exposed to the African-American music the city had to offer. They were well known performers in New Orleans in their young teens, and in 1925, they made their first recording. The landed in California in the late 1920’s. After their NBC appearances, they moved to New York, where they had a program on CBS from 1931-33. The sisters were also shortwave pioneers, appearing in 1932 in the first broadcast of “Hello, Europe,” a CBS program beamed to Europe.

They also appeared in a number of films. One of the earliest uses of the phrase “Rock and Roll” was their rendition of a song by that title in the film Transatlantic Merry-Go-Round in 1934, performed here:

Even though they are not well known today, the Boswell Sisters did have a lasting impact on American music. The Andrews Sisters started out as imitators of the Boswell Sisters, and a young Ella Fitzgerald was a great fan and patterned her own singing style after Connie Boswell.

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