This ad for a “Cathedral” radio from the Little Giant Radio Company of 1166 Diversey Pky, Chicago appeared in Radio Guide 80 years ago today, November 20, 1937.

The ad praises the set in near miraculous terms, and contains a number of glowing endorsements. Of course, the set is a simple crystal set. The “cabinet”, it turns out, is made of cardboard, and the earphone is mounted permanently right on the back. So to listen, you have to hold the whole radio up to your head.  The set had two large alligator clips, presumably to attach to an antenna and ground.  But it’s just $2.95, they would send it C.O.D., and your satisfaction was guaranteed.

More informaton, and a picture of the set, can be found in Volume 2 of Crystal Clear: Vintage American Crystal Sets, Crystal Detectors, and Crystals.  (Volume 1 and Volume 2 of that set are both available on Amazon.) You can also see some more photos of the set at this link.

As our loyal readers are aware, we often get off on tangents here at OneTubeRadio.com, but we always try to get back on track by showing actual One Tube Radios.  And the one we offer today has all the hallmarks of being an excellent performer, covering the range of 10-200 meters.

This is a one tube radio, since it uses a single 6F7.  But we’re cheating a little bit, not only because it’s a dual tube, but because the two halves of the tube are actually doing the work of three tubes.  The 6F7, which is still readily available at a reasonable price, consists of a pentode and a triode in the same envelope.  In this circuit, the pentode is used as an RF amplifier, with the triode serving as the regenerative detector.  But through the magic of “reflexing,” the pentode is then used a second time to serve as an audio amplifier.  The result is that the set gives the performance of three tubes, while only using a single tube.

The circuit originally appeared in the November 1933 issue of Shortwave magazine, in an article written by “well known shortwave engineer” Clifford E. Denton, who dubbed the set the “Triflex.”

For those wishing to duplicate the circuit, parts, or reasonable substitutes, should be readily available.  The new-old-stock tube can be found at this link.  You’ll probably need to make the plug-in coils yourself, but you’ll find helpful hints at this post.  Most of the other parts can be tracked down at my parts page.

Seventy-five years ago this month, the cover of the November, 1942, issue of Manitoba Calling, the program guide of CKY Winnipeg, carried this photo of two northern residents being kept company by their radio through the lonely winter.

With its 15,000 watt voice from Winnipeg, the station had become “one of the family” for many of those in Canada’s north, including missionaries, trappers, Mounties, doctors, nurses, and fur traders.

The magazine noted that during the First World War, many of these residents did not hear until the spring of 1915 that Canada was at war. But with radio, “a fur trader in his lonely cabin will hear the news and the latest developments on the war-fronts at the same instant that we in urban centres hear them.

The article noted that radio must still occasionally bow to atmospheric conditions, and the Aurora Borealis might occasionally wreak havoc on the standard broadcast band. But it also noted that when broadcast reception was poor, shortwave reception was frequently good, allowing northern residents to hear both American and overseas stations.

The service provided by CKY continues as part of CBC North.  While shortwave service ended in 2012, service is currently provided by a network of FM stations.

Fifty years ago, the November 1967 issue of Electronics Illustrated explained how the gentleman shown in this drawing could achieve his dream of seeing the world as a ship radio operator.

The article made clear that there were two conflicting priorities at work: The lines needed radio operators, but the unions had their own vested interest in keeping the supply tight.

Ships sailing under the American flag had to have a licensed radio officer aboard, and the lack of men sometimes meant sailing delays. One bottleneck was Vietnam. Two hundred ships had been called up from the reserve fleet. Many radio officers had been called back from retirement, and those on duty were being asked to forego vacations and leave.

Entry into the field wasn’t easy. Most American ships carried only one radio officer, but he had to hold a First Class license. But to get a First Class license, you had to have six months’ service at sea.

Because of the shortages, the Radio Officers Union recently started a limited training program. After six months, the man was ready to take an assignment on a one-man ship. After 18 months, he was entitled to full membership in the union. Base pay was $300 per month for the next six months, and then $600 per month for the next 18. After becoming a full member of the union, his pay shot up to $900-$1000 per month, with good benefits. Retirement, with about a third of the pay, was possible after just 20 years of service, regardless of age.

The magazine contained addresses of the union and companies for those interested in looking into a career at sea.

Eighty years ago, the November 1938 issue of Popular Mechanics showed this method of increasing your ground conductivity. The addition of water isn’t even mentioned in the text. But by adding the water, the ground near the rod becomes saturated, increasing the conductivity.

The actual hint being discussed is the use of a spark plug as a lightning arrestor. The lead-in is connected to one terminal of the spark plug, with the other end grounded.

Another hint shown in the same issue is shown here. Batteries are cheap enough these days that I don’t think it would be worth trying to put together this contraption, which doesn’t look very safe. But if you really want to run your small flashlight off AC power, then wiring it in series with a 25 watt light bulb, as shown, would do the trick.

The November 1937 issue of Popular Science carried the plans for this midget one-tube regenerative receiver for the broadcast band using a dual-grid type 49 tube.  The notable feature of the tiny set was that it employed only a single battery, a 3 volt “A” battery that powered the filaments as well as supplying the modest B+ voltage.

The low power requirement apparently meant that the set was just a bit finicky, since the article cautioned that many of the parts had to be exactly as specified in the article.  But when done, the midget tube set was said to produce good headphone volume with 10-20 feet of insulated wire tossed on the floor as the antenna.

The modest battery requirement meant that the set was ideal of hikers and campers, or for use in isolated areas without electric power.

Midget tube receiver schematic