Monthly Archives: January 2018

1948 Permeability Tuned Receiver

1948JanPS1Even though the war was over, it appears that aluminum was still in somewhat short supply, or at least expensive, in 1948, since it’s not unusual to see radios from that era using permeability tuning, which means that a variable capacitor was not required.

1948JanPS2Here’s one such example from the January 1948 issue of Popular Science. This little one-tube set uses a 12BA6 as a regenerative detector, with a 35W4 rectifier and “curtain burner” cord to run the filaments.  Tuning is accomplished by moving a slug through the coil, changing the inductance.  The complete coil assembly was  available as a commercial part, and was listed on the parts list as merely a “permeability tuning unit for regenerative circuit.”

The accompanying article didn’t include an explanation for hooking up the dial string, since the entire assembly was commercially available, and the other parts were simply squeezed in.

Interesting Math Relationships

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Today, we offer some fun math facts to amaze your friends.

You don’t need to be able to read the text to see these interesting mathematical relationships. This table appeared in the January 1958 issue of Юный техник (Young Technician).

Eunice Johnson, KOA Denver

1928JanRadioDigestShown here on the cover of the January 1928 issue of Radio Digest is Eunice Johnson of KOA Denver, described as “the most beautiful artist” in radio.  According to the magazine, she was “still in her teens, but she sings and talks to her audience like an old timer.”

The GE station signed on in 1924 with 5000 watts, increasing to 12,500 watts in 1927.  It went to its current power of 50,000 watts in 1934.

1938 Two-Tube Regenerative Receiver

1938JanSWTV11938JanSWTV2Eighty years ago, the January 1938 issue of Shortwave and Television magazine carried the plans for this two-tube regenerative shortwave receiver.  With plug-in coils, the set would cover 550 through 9 meters. The set used two 1.5 volt tubes: The RK42 triode served as regenerative detector, and a dual RK43 provided two stages of audio amplification.

The set was capable of pulling in stations from around the world, and “there is practically no limit to which this receiver will cover. So long as general receiving conditions are favorable, this little set will work wonders.”

The use of two variable capacitors allowed for bandspread tuning, and a variable resistor was used for regeneration.


1943 Coil Winding Tip

1943JanRadioCraft75 years ago this month, the January 1943 issue of Radio Craft carried this hint for winding coils.

The idea was sent in by one Tony Calabrese of White Plains, NY, and was billed as a good method for anyone to get a professional looking coil.

One end of a designated length of wire was attached to the wall or some other fixed object, with the other end attached to the coil form. After a couple of turns, the weight was placed on the wire to maintain tension.

When the coil was complete, the weight was slipped off, resulting in a neat coil with evenly spaced turns.

Recent Media Mentions

NewspaperImageWhile it didn’t mention by name, we were quoted in August by WJLA-TV in Washington, D.C.  In the excitement leading up the eclipse, I missed the article, but it covered many of the points addressed in our Take Your Kids To See the Eclipse post.

We were also privileged to be linked to by IEEE Spectrum for our description of the Luxembourg Effect.

Finally, this blogger recently wrote about our Elimination of Bias Continuing Legal Education programs.

Schoolhouse Blizzard of 1888

Today marks the 130th anniversary of the Schoolhouse Blizzard of January 12, 1888.

After a long cold spell over the Northern Plains, the temperatures advanced considerably. For example, Omaha had recorded a low of −6 °F on January 11, but the temperature had increased to 28°F at 7:00 AM on January 12.

The warm weather after a long cold spell perhaps gave the illusion that relief was in sight, but the conditions deteriorated during the day of the 12th. Thousands of people got caught in the blizzard, and the ultimate death toll was 235.

Most schoolteachers kept the children in school that afternoon, and exceptions almost always resulted in disaster.

GE Shortwave Stations, 1943

1943Jan11LifeThis full-page ad by GE appeared inside the front cover of Life magazine 75 years ago today, January 11, 1943, and told the importance of the GE shortwave stations, KGEI, WGEO, and WGEA.  In addition to being a link to home for the armed forces, the stations broadcast “from a free people to men with freedom in the hearts” in Asia and Europe.

1967 Homemade Electronic Bug


Fifty years ago this month, the January 1968 issue of Electronics Illustrated offered just the thing for aspiring spooks, namely, this homemade electronic bug. Housed in the ubiquitous cigarette pack, the tiny device transmitted on the AM band, and could be picked up 10-50 feet away.

It was billed as suitable for listening in on “your neighbor, close friend, worst enemy, bookie, business partner, the business competition, or even you.”

As shown here, the parts had a price tag of about $20, although the article noted that the price might be lower if slightly larger components would be acceptable.

The circuit used four Motorola transistors, three 2N4123’s and one MPS3646 handling the RF output duties. It was constructed on a circuit board with holes drilled for the components, with wiring on the other side.

The battery shown here is a Burgess H-177 9.8 volt battery, although the article pointed out that a standard 9 volt battery could be used if the slightly larger size were acceptable.

1918 Ground Current Telegraph

1918JanPS1With civilian radio (both transmitting and receiving) shut down for the duration of the war, hams a hundred years ago still had a desire to engage in communications. As we’ve seen prevsiously (here, here, here and here), one method of communicating without the use of radio waves is a ground-conduction telegraph. And a hundred years ago this month, the January 1918 issue of Popular Science showed how to do it.

The magazine noted that “because the Government, for good and sufficient reasons, has put a ban on amateur wireless stations, it does not follow that all your activities must stop.” It noted that communicating by ground wireless was “almost as interesting” as actual radio and was “permitted by the Government, since high tension apparatus need not be used, at least not in their normal capacities.”

While the magazine noted that the Allies were apparently not using this type of communication, “for all we know the Germans may be using it now,” and that it had a potential range of forty miles, and perhaps more through salt water.  (The 40 mile estimate seems extremely optimistic, but I can’t say I’ve ever tried it.)

1918JanPS2In addition to the basic circuit shown above, the magazine also showed this more advanced setup, which permitted full break-in operation (with the addition of a normally-closed contact to the key).  It looks just slightly dangerous, and would probably trip a modern ground fault interrupter.  It doesn’t appear to send any signal over the power lines, but does use the electric service ground as one of the two connections.