Category Archives: Radio history

Line Voltage Booster

1979MayPEThis was by no means a new idea at the time, but the May 1979 issue of Popular Electronics shows a simple way to boost your line voltage. It employs a six-volt filament transformer wired so that it becomes an autotransformer, and the voltages on both coils add. So if you start with 120 volts, you wind up with 126. As the accompanying text explains, you might need to use some trial and error. If you wire it up and the voltage goes down by six volts, then you need to reverse the secondary windings.

While they are not common, 6 volt filament transformers are certainly not unobtainium, and you can get them from Amazon at this link:

If you need a slightly heavier duty version already assembled, then you can’t go wrong with an adjustable autotransformer (commonly known as a variac) like this one:



1934 Try-Mo Scout Shortwave Receiver

1934MaySWcraftScoutThe May 1934 issue of Short Wave Craft magazine included this ad for the “Scout,” a one tube shortwave set from the Try-Mo Radio Co., Inc., of 85 Cortlandt Street, New York.  The set sold in kit form for only $3.95, but the type 230 tube, batteries, and headphones would run an additional $4.25.  The set came with plug-in coils for shortwave, but a coil for the standard broadcast band would cost an additional 39 cents, probably a good investment in case the short waves were quiet.



1944 WERS Transceiver

1944MayQSTSeventy five years ago this month, the May 1944 issue of QST carried a construction article for this 112 MHz transceiver for the War Emergency Radio Service (WERS). The article was unique in that it showed how to “mass produce” the set in a high school shop class.

The Altoona, PA, WERS organization operating under call sign WKYU, had little appropriate equipment. Compounding the problem was the fact that few skilled amateurs remained at home to do the building. The problem was solved by setting up construction of standardized transceivers by radio and electronics students in the vocational department of Altoona High School. The school benefitted by having interesting and worthwhile lab work, and WERS benefitted by having a source of the needed equipment. In addition, the students who were involved in WERS also had particular pride in using equipment they themselves had built.

The circuit is a familiar one for VHF transceivers of the era. A 6J5 served as oscillator and self-quenched superregenerative detector, although other tubes could be substituted. A 6G6 pentode served as modulator and audio amplifier. Since wartime shortages meant that some tubes were not available, the article suggested substitutions for each.

1944MayQSTschematic



1929 Soviet Portable Receiver

1929SovietPortable1929SovietPortable2I wish I was able to read more about this 1929 Soviet portable set. But the text is in Russian, and the quality of the scan is rather poor, so I can’t even make out any words to give me hints. But this is obviously a portable receiver from ninety years ago, and some lucky comrade was able to put it together and pull in the signals.

The set appears to be a two-tube regenerative receiver which fits handily into a suitcase.  One tube servies as detector and the other as audio amplifier.  The circuit appears to be regenerative, with a tickler coil feeding the signal back into the main antenna coil.  Tuning is accomplished with a tapped coil and variable capacitor.  The cut-out in one corner is obviously to stash the batteries, and perhaps the headphones and antenna wire.

The plans for the set appeared 90 years ago this month in the May 1929 issue of Радио любитель (Radio amateur) magazine.

1929SovietPortableSchematic



Phonographic Spam Sales, 1939

1939MayRadioRetailingEighty years ago this month, the May 1939 issue of Radio Retailing carried this feature explaining how salesmen from Austin, Minnesota, based Hormel Foods did their jobs.  To tell the story of “a new canned meat,” the salesmen brought along on their calls to grocers a portable phonograph and played a record of the canned meat’s story.  They “stood speechless while the record did the selling, softened up the prospect with suitable musical interludes.”

This salesman was employing an Emerson radio-phono.

While the meat is not identified in the caption, it is plainly visible in the photo, which reveals that the phonographic sales pitch was for Spam, the venerable luncheon meat which had been introduced by the company in 1937.



D-Day Preparations

1944May20MilJournSeventy five years ago, the exact time and place of the D-Day invasion was a closely guarded military secret, but the fact that is was coming soon was no secret. 75 years ago today, the May 20, 1944, issue of the Milwaukee Journal carried this headline that Gen. Eisenhower had issued his first orders to the Underground.

The orders went out over American radio stations recently constructed on the continent.  The commander-in-chief advised the underground to take minute and detailed note of every move of the enemy, with particular attention to the moves of his men, tanks, guns, as well as their markings and strength.

When this was published, the invasion was just over two weeks away.



Boys’ Life SWL’ing, 1969

1969MayBLFifty years ago this month, the May 1969 issue of Boys’ Life carried a one-page primer on shortwave listening. It coached scouts on the basics of the hobby. The article noted that you could get started with a portable or table radio, but for the best experience, it recommended a communications receiver in the $100 price range. The bandspread was identified as the most important feature.

The article noted that the lower frequency bands up to 25 meters were best at night, with the higher frequencies being best during daylight hours.

It noted that it was possible to listen in on both U.S. and Soviet space shots, and noted that the frequencies of 17,655 and 20,186 kHz were the most likely.



1944 One Tube AC-DC Receiver

1944MayRadioCraftSeventy-five years ago this month, the May 1944 issue of Radio Craft carried this simple one-tube AC/DC circuit sent in by one Bob Smith of Montclair, NJ.  The set uses a single 12A7 tube as rectifier and detector.  According to Smith, the set would perform on either the standard broadcast band or on shortwave, with appropriate plug-in coils.

The filament voltage is dropped through a standard light bulb, although the schematic shows 70 watts, and the text shows 40 watts.  I suspect 70 watts is the correct value, but we’ll leave it up to the reader to do the calculations.



Radio’s Geography

Screen Shot 2019-05-08 at 9.59.43 AMEighty years ago, the May 15, 1939, issue of Life Magazine introduced readers to the sometimes counter-intuitive geography that comes from living on a globe. In particular, the magazine noted that it was important for shortwave broadcasting.  For example, it pointed out that the first reaction on how to reach Manila from New York would be to point the antenna toward Mexico and the Pacific.  But by looking at a globe or an azimuthal map centered on New York, it’s clear that the shortest path is over Alaska.

Similarly, the magazine notes that it’s easier for Berlin radio to reach South America than it is for New York.  This is because to reach the entire continent, the American station needs to have a beam 40 degrees wide.  The German station, on the other hand, can get by with only half the power, since most of the continent can be covered with a beam of only 20 degrees.

Screen Shot 2019-05-08 at 10.00.12 AM

It’s not a coincidence that New York and Berlin were chosen as the examples.  Shortwave radio was an important force in World War II.  For more information, see our earlier post.



WMTW, Mt. Washington, 1944

1944May15BCThis ad appeared 75 years ago today in the May 1944 issue of Broadcasting. It shows the facilities of WMTW, one of the stations of the Yankee Network’s FM network, broadcasting from Mount Washington, New Hampshire.

The network relied upon daisy-chaining the signals, and WMTW received its signal from WGTR, Paxton, Mass., 142 miles away, on 44.3 MHz, and rebroadcast on 43.9 MHz.