Ninety years ago, the April 1926 issue of Radio In The Home magazine carried the plans for the “200 Mile” crystal set shown below.  The author describes the set in the following terms:

Many readers will be surprised to learn that a simple crystal set has given a fairly consistent nightly range of more than 200 miles. Yet this is not unusual; it is just the average performance of a well designed crystal set and has been done repeatedly this and the latter part of last winter.

From our location in Niagara Falls, New York, with an aerial and location no better than the usual, we have regularly listened to Pittsburgh, 200 miles, to Schenectady, 250 miles and to Chicago, 450 miles.

This record may seem out of the ordinary and indeed we ourselves were surprised at first. But the manner in which the first set and others of the same type, used on our own and other people’s aerials operate, has convinced us that the feat may be duplicated almost at will.

It then goes on to describe the set, emphasizing how low-loss components are used throughout.  Any detector could be used, but for best results, “it should also bear a certain relation (rather difficult of exact specification) to the input impedance. These conditions can best be met through use of the electrically controlled carborundum permanent detector (Carborundum Stabilizing Detector Unit).”

The Carborundum Stabilizing Detector Unit was manufactured by the country’s only producer of carborundum (silicon carbide), the Carborundum Company, which just happened to be also located in Niagara Falls, New York.

The carborundum detector does have the advantage of being permanently fixed, with no cat’s whisker to fiddle with.  It requires a reverse bias, provided by a flashlight battery.  The Carborundum Stabilizing Detector Unit included a potentiometer for adjusting the bias voltage.  So the listener accustomed to fiddling with the cat’s whisker could instead fiddle with the potentiometer.

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Here’s what the well equipped audiophile would have in his living room 75 years ago. The receiver is unmistakably made by National, and it’s shown in the April 1941 issue of FM magazine.

The ad’s caption conceded that the set was designed primarily as a communication receiver, but that it gave superb FM rception.  It had dual high fidelity output circuits, an excellent signal to noise ratio, and extreme sensitivity.  The ad doesn’t say so, but it would look nice in any living room.

Unfortunately, I haven’t been able to identify the model number, or even whether this receiver actually made its way into production.  According to the ad, the set was described in the December 1940 issue of the magazine, but that issue isn’t available online.

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Eighty years ago, the well equipped radio service shop could very well have been equipped with a Wobbulator. Shown here, in the April 1936 issue of Service magazine is the Model 180 Wobbulator, manufactured by the Triumph Manufacturing Company of 4017 W. Lake Street, Chicago.  The unusual name is for a signal generator covering 100 kHz to 30 MHz.

The Wobbulator should not be confused with a Gonculator, a device used only on submarines.

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Taking the code test in 1926.

The April 1926 issue of Popular Radio contains an interesting article detailing the requirements to get an amateur radio license 90 years ago. Written by prolific author Howard S. Pyle, 7HP, W7ASL, and W7OE, the article notes that examinations were given at the various radio inspection offices on a regular schedule. In Detroit, for example, Amateur exams were given on Saturdays starting at 10:00 AM, “and it is wise to appear promptly at this time, for the examining officer dislikes to be compelled to run the code test again for late comers.” It also explains that for those living in outlying areas, a temporary permit could be issued based upon a questionnaire and sworn affidavit of code ability, to be followed up by a personal examination at a later date.

The code test was originally set at “an arbitrary speed of five words a minute, … but experience proved it to be too slow.” Therefore, the speed as of 1926 was 10 words per minute, meaning 50 characters per minute. “An applicant is really offered five opportunities to demonstrate his ability,” since a single minute of solid copy was all that was required. “It is assumed, however, that he will put down a reasonable portion of the balance, in addition to the required number.”

Until a few years earlier, no sending test had been required. But “large numbers of operators, notably at sea, were later found, on observation, to have extremely poor ‘fists’ as their sending hand and style is termed in radio phraseology,” including the “Lake Erie Swing.” Therefore, a sending test was also required.

The code test out of the way, the applicant was then tested on his knowledge of radio theory. This test was based not upon a transmitter “you’ve seen on a steamer or in a broadcast station, but the one that is actually on your own operating table.”

Therefore, the first part of the test was to prepare a complete diagram of the transmitter, receiver, and source of power. “This must be complete in every sense of the word.” Then, the applicant was to explain to the inspector how it worked.

This does not mean that you are to say, “I throw my antenna switch to the transmitting position; cut in my power and work my key.” What is wanted is something like this:

“Using the alternating current of the house lighting circuits, through the medium of a setp-down transformer, the filament of the vacuum-tube oscillator is brought to incandescence, thus emitting an electron stream, which is caused to flow to the plate by reason…”

The remainder of the exam consisted of showing similar familiarity with the radio laws, operating procedures, Q signals, and other items deemed important by the examiner.

Pyle concludes:

Let the aspiring applicants to the “blue ticket” of the full-fledged amateur be encouraged and may the great fraternity remain foremost among the country’s youthful experimenters!

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Seventy-five years ago today, the April 7, 1941, issue of Life Magazine carried this ad for the model L-500, as a second set for the study or den, with which you could enjoy your own program, while the family enjoys theirs on the big set in the living room.

The set was a basic “All American Five,” with a tube lineup of 12SA7, 12B7, 12SQ7, 50L6GT, and 35Z5GT tubes.  This set was ready to tune the entire broadcast band, with coverage up to 1700 kHz.  With the recent NARBA reallocations, the band now extended up to 1600.  The speaker was four inches, and the plastic cabinet was award winning, having “won the top award for styling in the nationwide Modern Plastics contest.”

A nicely preserved specimen of this set can be found at the Radio Attic Archives, courtesy of the California Historical Radio Society,

Also shown in the ad is the Model J-602, a restored example of which can be seen in this video:

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Yesterday, we presented the problem shown above and promised that we would show the solution today.  The problem isn’t particularly difficult, and there are probably other ways to do it.

Since 15 volts is measured across the 30K resistor (and R2), this means that 30 volts is dropped across R1, which happens to be twice as much as 15.  This means that R1 is twice as large as the combined parallel resistors.  Since only the ratio is important, it’s easier to work in kilohms rather than ohms:

R1 = 2 (30 R2 / (30 + R2))

We’re also told that R1 + R2 = 15.

They might look a bit messy, but we now have two equations and two unknowns, meaning that we can solve them.  In my scribbling below, I used the variables X and Y to keep things a bit more legible.

After crunching the numbers (including use of the dreaded quadratic formula), we arrive at the answer:

R1 = 9416 ohms, and R2 = 5584 ohms,  [See the comment from eagle-eyed K3CHJ who caught my earlier typo!]

the same answer given in the June issue.  So when you asked your poor sainted algebra teacher, “when will we ever have to use this in the real world?,” he or she should have pointed out that you might need it someday for your blog.

During the 1950’s, QST ran a regular feature called Quist Quiz, which presented an electronic brain teaser. This one appeared in the May 1959 issue.

I’ll provide the solution tomorrow.  If you can’t wait, you can look in the June 1959 issue, where the answer (but not the full solution) is shown.

Unless you want to do a lot of trial and error, you’ll probably need to use the quadratic formula,  Back in the day, the 1959 ham probably had to go dig out his old algebra textbook.  Today, you can just click on the link and Wikipedia will help you.