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Vintage Radio
WSHU Chief Engineer Paul Litwinovich explores aspects of vintage radio, from the radio sets themselves to the people and technology that made it all possible.

A Radio for the Great Depression


Last month we looked at the RCA Radiola 46, a lavish high end radio that went into production in the spring of 1929, about 6 months before the October market crash that began the Great Depression. This month will be the first half of a two part article in which we will look at how radio faired in those difficult times and how RCA in particular changed its business philosophy to survive.

The story actually begins with Edwin Armstrong (*1) in 1918. He probably contributed more to the technological development of radio as we know it today than anyone else. Born on December 18, 1890, in New York City, he graduated with a degree in electrical engineering from Columbia University in 1913 and went on to serve in the US Army Signal Corps. In 1918, while serving in France, he developed the concept for the heterodyne receiver. The circuit mixes a locally generated signal with the received radio signal to create a third signal that can be filtered and amplified to produce good reception while rejecting unwanted signals and interference. I’ll get into how it works in the second part of this article. Armstrong was also experimenting with the regenerative circuit at the same time as Lee Deforest and both claimed to have invented it. The resulting patent litigation, which Deforest eventually won, cost both men a substantial portion of their fortunes. 

After leaving the service in 1920, Armstrong sold his patent for the heterodyne circuit to Westinghouse for $335,000, (*2) which was a huge sum of money for a patent at that time. Westinghouse had just put station KDKA (note 1) on the air in Pittsburgh, Pennsylvania and was very interested in circuits to improve reception.

David Sarnoff in 1922

Armstrong first met David Sarnoff(*3) at a boxing match involving Jack Dempsey in 1920. At the time, Sarnoff was a young RCA executive with an interest in new technologies, including radio broadcasting.  In the early 1920s, Armstrong  is said to have driven off with Sarnoff's secretary, Marion MacInnes, in a French sports car. Armstrong and MacInnes were married in 1923. Coincidently, in that year, RCA bought the heterodyne patent from Westinghouse. It is not documented that Armstrong convinced Sarnoff to buy the patent, but it is generally believed amongst radio enthusiasts that he did.  Mr. Armstrong was never formally employed by RCA but he did have a love-hate business relationship with David Sarnoff over the next 30 years and frequently worked for RCA as a consultant. Limitations with early 1920s tube technology prevented either company from producing a cost effective version of a heterodyne receiver, and Westinghouse may have realized this at the time they sold RCA the patent.

RCA advertisement for 1924 Radiola AR812

RCA did produce a commercially available heterodyne receiver (now trade named "Superheterodyne" by RCA), the Radiola AR218, in 1924. It performed well, but due to limitations of tube technology did not outperform other circuits sufficiently to justify its high cost in the minds of the average consumer. So, they shelved the circuit for the time being. The radio did demonstrate, though, a new trend in RCA’s business philosophy. Apart from the tubes and controls, the entire workings were encased in a hard wax, to prevent competitors and hobbyists from reverse engineering and copying it.

Credit P. Litwinovich collection
Radio 18 Schematic

The policy of concealing  trade secrets and improvements continued. In 1927, RCA inserted a regenerative loop (note 2) into the otherwise normal looking Tuned Radio Frequency (note 3) circuit in the Radiola 18. The added circuit did not appear on the schematics or service information and RCA required that all warranty repairs be returned to the factory as opposed to being serviced by the dealer.  After being set at the factory, an adjustment control for the circuit was covered over by the identity sticker on the bottom of the set. The schematic shown here is the one included with the radio. I used editing software to draw the secret circuit in red, which did not appear in service manuals until the early 1930s. While concealing trade secrets that give a company an advantage over its competition is certainly an acceptable practice, the fact that Edwin Armstrong was at the time embroiled in patent litigation with Lee Deforest over the regenerative circuit, raises ethical questions over why RCA concealed the circuit. Neither Armstrong nor DeForest were paid any royalties for the use of the circuit, which gave the Radiola 18 substantially better performance than its competitors. (note 4)

In 1929, the screen grid tube was introduced. It was the answer to how to produce a cost effective heterodyne circuit. The market also crashed in October of that year, beginning the Great Depression. To add to the pain and suffering caused by a serious economic crisis, the central plains, the agricultural "bread basket" of the nation, would soon be struck with a prolonged drought that became known as "the dust bowl years."  The demand for what radio had to offer increased sharply. People suddenly turned to broadcast media as a source on what was happening with the economy, the drought, job availability, sales in stores, etc. Radio also gave the masses a distraction from hard times in the form of the music, variety, adventure, and comedy shows of the times. (*4).   Demand for such shows brought many new stations to the air, and businesses soon saw the value of reaching the masses with relatively affordable advertising rates sponsoring the programs. The problem facing the radio manufacturers was how to meet the demand for low cost, high performance radios that people facing hard economic times could afford.

Enter the superheterodyne circuit. New tube developments allowed for the design of  less expensive heterodyne sets with a minimum of components. Sets that were so powerful that many of them no longer required the use of an outdoor long wire antenna. RCA could have had a monopoly on the production of such sets, holding the patent for the heterodyne circuit, but David Sarnoff decided to do something different and totally uncharacteristic for RCA.  He decided to license the patent to any manufacturer willing to pay royalties for using it. RCA itself produced superheterodyne sets and marketed them successfully, but made far more money from licensing the heterodyne circuit to others. If you find almost any radio made by a company still in business when the country started to emerge from the depression, and for years thereafter, its label will say "Made under patents licensed from The Radio Corporation of America."  Although the RCA patent has long since expired, Edwin Armstrong’s circuit is still used today in almost every communication device from your radio to your smart phone. Next month we will look at how the heterodyne circuit works, and some of the classic radios that used it. We will continue to look at how the radio industry adapted, or in some cases failed to adapt, to survive the Great Depression.

Note 1. For more on KDKA, see my article Order Out Of Chaos  Jan, 2014

Note 2.  The regenerative circuit  was popular in the late teens and early 1920s in consumer radios, and remained popular with hobbyists and amateur operators for a long time after that.   Read more about it in several of my earlier articles including Regeneration Under Glass March, 2014.

Note 3.  TRF,  The Tuned Radio Frequency circuit was the circuit of choice for most manufacturers in the 1920s, read more about it in several of my earlier articles.

Note 4. RCA never paid royalties to DeForest or Armstrong for regenerative technology, and openly cheated Armstrong out of royalties for his development of FM technology at a later date. The  prolonged, drawn out litigation in later years was attributed in part to Armstrong committing suicide in 1954. Armstrong’s widow Marion, however, went after RCA with a vengeance. She successfully won lawsuits and was paid substantial royalties for several of Edwin Armstrong’s patents.  Mr. Armstrong’s biography is available in detail from multiple sources online, some listed below.


(*1) Edwin Armstrong &       

(*2) Armstrong Biography, Originally published in Dictionary of American Biography, Supplement Five, pp. 21 - 23; Charles Scribner Sons, New York, available online at:    

(*3) David Sarnoff: David Sarnoff library,  & IEEE archives,

(*4)  A list of 1930s radio shows is available at:

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