Category Archives: Radio history

More 1940 FM Radio

GEHM136

Seventy-five years ago, one apparently dressed up to listen to the radio, especially if you were listening to static-free FM. As related in an earlier post, FM was just starting to gain a modest foothold prior to the war. FM then operated on 42-50 MHz. The Milwaukee station, for example, was on 42.6 MHz. After the war, the FCC moved FM broadcasting to its current home of 88-108 MHz.

To enjoy static-free FM reception, listeners had to get a new radio. At the very least, they would have to get an FM tuner which could plug in to the phono input of their current receiver. The choices were somewhat limited, but many of the major manufacturers came out with at least one FM receiver.

General Electric’s top-of-the-line offering is shown here. It is the HM-136, and is shown in an update on FM in the May 1940 issue of Radio Today.

In addition to the FM band, the 13-tube model covered the standard broadcast band and two shortwave bands, 2.4-7.5 MHz and 7.5-22 MHz. Interestingly, the set didn’t tune the entire prewar band. It tuned only 39-44 MHz, meaning that it wouldn’t be of use in areas with stations higher in the band. Fortunately, however, the existing stations were below 44 MHz, even though the larger band was allocated.

A schematic and service information for the set can be found at Antique Electronics Supply. I haven’t found links to modern photos of surviving examples.

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1940 Postcard Radio

PostcardRadio1Seventy-five years ago, the May 1940 issue of Popular Science carried the plans for this novelty crystal set that was suitable for mailing as a letter. You could slip it into an envelope “and mail to one of your radio-minded friends as an amusing birthday or holiday greeting.”

The radio was sandwiched inside two postcards, with the detector and taps for the tuning coil exposed. Connections for antenna, ground, and headphones were made to paper fasteners which also held the “chassis” together.

To keep it flat, the coil was wound “spider web” style, with four taps for tuning. Blobs of solder were left exposed, and a “crocodile clip” was used to make the connections.

The whole radio could be mailed for six cents.  The schematic is shown below:

PostcardRadio2

All of the parts for this set should be easily obtainable. If you need help finding any (the most difficult to find would be the high-impedance earphone), I have sources on my crystal set parts page.

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WCCO Radio in 1925

WCCOstudio1925For those interested in the early history of WCCO radio in Minneapolis, the May 1925 issue of Radio Age carried a feature on the station as it was 90 years ago. The station had just put into service its new 5000 watt transmitter, what the magazine called “one of the super broadcasting units.” It also noted that the Minneapolis studios at the Nicollet Hotel were “said to be the equal both in equipment and elegance of anything in the country.”

In addition to the Minneapolis studio, the station had just begun construction of a studio in St. Paul, which would probably be “the most unique location of any studios in the world, for they will be in Saint Paul’s handsome new Union Depot used by nine railroads.”

The transmitter was at the station’s current transmitter location, 18 miles northwest of Minneapolis in Anoka. Special telephone lines connected the studios and transmitter.

The station had come on the air in October 1924, using the equipment of the former WLAG.

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Hallicrafters TV in Cuba, 1952

HallicraftersCuba

The magazine Radiomania y Television gives an interesting look at pre-revolution Cuba.  This Hallicrafters TV ad appeared in the January 1952 issue.  In addition to the equipment ads, it gives an interesting look at the programming, which appears to have been mostly produced in Cuba.  In addition to about two dozen standard broadcast stations, the island had one FM station (CM2IL on 102.7 MHz) and two TV stations, CMUR-TV, channel 4, and CMQ-TV, channel 6.

Interestingly, the Hallicrafters dealer seems to have an indirect connection with the revolution.  As seen in the ad, the exclusive Hallicrafters dealer was Cia. Cubana de Refrigeracion Electrica, S.A.  About this same time, the bookkeeper at the company was one Reinaldo Boris Luis Santa Coloma.  At some point, he lost his job for trying to organize a union, and later got a job at Sears.  At some point in 1952, he was at the law office of a young attorney named Fidel Castro, where he met his mistress and the mother of his child.

The next year, he was one of 135 revolutionaries who, along with Castro, attacked the Moncada Barracks, which is widely regarded as the start of the Cuban Revolution.

References

 



The Army Hour, NBC Radio, 1945

1945NBCfamily

The family shown in this photo appeared in an ad for the NBC network in the April 1945 issue of Tune In magazine.  They are gathered around the family console, which is adorned by a photo of their young serviceman. The ad notes that NBC acts as a two-way pipeline between the men of the armed forces and their families back home. Not only do the servicemen tune in to their favorite NBC broadcasts via the regular network and shortwave, but NBC also broadcasts for the people at home the “Army Hour,” a weekly production of the War Department and NBC.

The picture was undoubtedly taken at 3:30 Eastern War Time on a Sunday afternoon, when the Army Hour was broadcast.

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Emergency Telephone Hookup

PhoneIntercom

It’s a relatively trivial matter to hook up two telephones so that you can talk from one to another. Virtually any old telephone can be used, and it’s simply a matter of placing a battery (the voltage is not critical) in series. So if you need to hook up two telephones to talk, it’s about as easy as it gets.

It’s more difficult, however, to figure out a way to make the other telephone ring. The telephone itself operates off DC. The ringer sounds when an AC voltage is applied. And there’s no particularly simple way of generating that AC voltage. The easiest way to solve the problem is to run a second circuit with a bell, buzzer, or light. If you want to talk to the other station, you push a button, a bell (separate from the phone) sounds at the other end, and the other person picks up the phone.

The ingenious arrangement shown above shows a way to wire it all up so that a single circuit can handle both the bell and the telephone line. When one station wants to call, he pushes the button to signal the other station. Then, both sides put the switch on position 2, and they can talk. This circuit, and all the details for constructing it, are found in the April 1966 issue of Radio Constructor, a British electronics magazine.

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FM Comes to Milwaukee, 1940

W9XAO

75 years ago today, April 22, 1940, FM radio came to Milwaukee, when W9XAO came on the air at 1:00 PM on 42.6 megacycles. The station was owned by the Milwaukee Journal, and was the sister station of WTMJ, the paper’s standard broadcast station. According to the April 21 issue of the newspaper, the station was “the first FM station west of the Alleghenies.”

The paper used a number of pages touting the advantages of FM radio. Of course, listeners would require a new set to tune in the new band, and a number of manufacturers and retailers advertised their sets. The least expensive model was Stromberg-Carlson model 525-H for $59. This radio was actually a tuner only. It could be plugged in to the phonograph jack of an existing radio.

The station at some point received a commercial license and operated under the call letters W55J. After the war, the station moved to 102.1 on the modern FM dial with the call sign WTMJ-FM, but ceased broadcasting in 1950. WTMJ-FM returned to the air in 1958, on 94.5 MHz. The station is currently still owned by Journal Communications, but now uses the call sign WLWK-FM.

Don Stanley

Don Stanley

The first full-time announcer at W9XAO was Don Stanley, who came to Milwaukee from KGLO in Mason City, Iowa. He went on to become a west coast announcer for NBC radio and television from 1946-1992.

Edit:  See correction in comments below.  Stanley came to Milwaukee from Madison, WI, and not from Mason City.  His daughter has created this Facebook tribute page.

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Science Fair Idea: Measuring the Speed of Sound

Measuring the speed of sound with an oscilloscope.

Measuring the speed of sound with an oscilloscope.

In an earlier post, I gave some ideas for young mad scientists to employ for science fair projects. Another idea comes from the pages of the April 1966 issue of Radio Constructor, a British electronics magazine. The article explains two methods of experimentally measuring the speed of sound. One of those methods requires an oscilloscope, but the other one requires only an AC voltmeter.

Measuring the speed of sound with an AC voltmeter.

Measuring the speed of sound with an AC voltmeter.

Fortunately, the young experimenter of today can duplicate either of these experiments quite easily. For the version of the experiment requiring an AC voltmeter, most modern digital multitesters would be very suitable, and they are often available for next to nothing. The following examples are currently available at Amazon:


Harbor Freight
often has multitesters on sale, or occasionally for free. They’re also available inexpensively at WalMart.

The oscilloscope is more expensive, but still a lot less expensive than 1966. For example, this USB Oscilloscope can be used with a PC for a reasonable price. And while a bit more do-it-yourself work would be required, this USB oscilloscope is also very inexpensive.

The only other equipment required is an audio signal generator (for which you could easily use your computer’s sound card) and an audio amplifier, such as this one. The other required parts, such as speakers, can easily be scrounged up.

Using either method, it’s fairly simple to measure the wavelength of the audio signal. Since the frequency is known, it’s then an easy matter to calculate the speed of sound, which would be frequency times wavelength. The possibilities for using this as part of a science fair project are unlimited. For example, it would be possible to measure the speed of sound under various conditions, such as with differing barometric pressures or altitudes. By waterproofing the speakers, it would be possible to measure speed of sound in water, and compare it to the value in the air.

In any event, your poor teacher is probably tired of seeing paper mache volcanoes, and will probably be quite impressed at your abilities.

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Radio Station WAR, 1945

WARtapemachineSeventy years ago, April 1945, Popular Mechanics carried a feature about the War Department’s Signal Center in Washington and its radio station, which bears the call letters WAR. The article noted that the station at this nerve center of the War Department handled 8-9 million words per day, with direct hookups to forces throughout the world. The WAC operator shown here is overseeing tapes on an automated code sending machine. At the other end of the circuit is the station at Bougainville shown below.

 

Bougainville

The call sign WAR is heard on the airwaves at least once a year during the annual Armed Forces Day Cross-Band Communication Test when the station, along with other military stations, makes contact with amateur operators.

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Yukona Cameron, WQJ Chicago, 1925

YukonaCameron

Shown here is Miss Yukona Cameron, a singer who appeared nightly on WQJ in Chicago. The caption of this photo from the April 1925 issue of Radio Age notes that she often favored her audience with old-time selections, but that she received the most requests when she presented a popular ditty.

According to an article in the May 17, 1925, Chicago Tribune, the station had come on the air on May 22, 1924. It was owned by Calumet Baking Powder Company and the Rainbo Gardens Ballroom and broadcast from the Rainbo at 4812 North Clark Street.  Interestingly, when the building was finally torn down in 2003, a collection of human bones and tennis shoes were discovered in what had been the building’s basement. The mystery of how those bones ended up there has never been solved.

WQJ shared time at 670 on the dial with WMAQ until it was finally bought out by WMAQ in 1927.

After the station closed, Miss Cameron appeared in two Broadway shows in 1927 and 1930. In 1935, she was back in Chicago, at least for one engagement. According to the Chicago Tribune, August 4, 1935, she was appearing at the Palace, doing a show with comedian Al Trahan, with whom she also appeared in the 1930 short film The Musicale.

Trahan and Cameron, in addition to being Vaudeville partners, were also husband and wife. According to the Palm Beach Daily News, Feb. 20, 1934, the pair had performed before King George, who reportedly remarked, “that American made me laugh.” They had also performed for King Gustav of Sweden and the Prince of Monaco.

Miss Cameron owed her first name to the fact that she was the first White child born in the Yukon, where her parents were prospecting for gold. She was a musical prodigy, and was a concert pianist at the age of 18 with the Chicago symphony.

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