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Radiola 16

The Radiola 16 was introduced in August of 1927.  It was RCA’s first new model specifically designed to operate with 201A tubes ... and it was the last.  It was also their first single-dial TRF.

Radiola 16 schematic

The Radiola 16's circuit is almost identical to the 1926 Atwater Kent model 30 (November 1925) with an untuned RF stage followed by three tuned circuits and a grid-leak detector.  They also copied Atwater Kent's use of damper resistors in the RF grids and orthogonally mounted coils to reduce feedback. 

Radiola 16 bathtub condenser assembly and orthogonally mounted RF coils

The only two other RCA sets to use 201A tubes were recycled versions of older models: the Radiola AR - Option 2 and the Radiola VI,[1] both of which were in very limited production during the 1923 season only.

There were seven models designed to use the predecessor of the 201A (the 201), but they were all dropped by the end of the 1923 season. 

The primary difference between the 201A and its precursor, the 201, was filament current; the 201 drew one amp while the 201A drew only .25 amp.[2]  The 201 and 201A tubes were reliable and convenient.  Both 201 and 201A filaments were designed to run on a conventional six-volt automobile battery.  But, since the 201A tube drew one-fourth the current of a 201, a radio could be used four times longer before the battery needed re-charging.  And because of its thoriated tungsten filament, reliability of the 201A tube is phenomenal and emission is higher.  We’re using 85 year-old 201As in a 1924 Atwater Kent model 20 that gets played every day.  They seem to last forever and there’s no shortage of them. 

Between 1924 and 1926 everyone it seems, except RCA, used 201As; the question is, why?  The rest of the RCA tube line offered no such value.  The reliability of the WD11 tube was abysmal.  It’s rare to find good ones.  Conversations with people who mail-ordered new ones in the early 1920s are filled with stories of long waits only to receive tubes with broken filaments.  Reliability of the 199 and 120 tubes was slightly better than the WD11 but certainly not on par with the 201A.[3]

Since the filaments of the WD11, WD12, 199, and 120 tubes were all designed to run on dry cells, the average user would not have had a renewable source of filament voltage.  Dry cells were not rechargeable, making them an expensive luxury. 

So why did three years of RCA production abandon one of the most popular and reliable tubes in history?  Between 1924 and 1927 companies like Atwater Kent, FADA, Freed-Eisemann, and Freshman sold an estimated ten million three-dial TRF radios populated with 201A tubes.  RCA should have been able to produce an inexpensive set with the same features, but they chose not to.
The reason for RCA’s tube complement from 1924 through 1926 could have been their perception that America preferred to operate a radio with dry cells hidden inside rather than messy and cumbersome six-volt storage batteries.  This may have been true of apartment dwellers in New York and New Jersey, but the rest of the country needed the reliability of the 201A and the renewable power source provided by their automobile or tractor battery. 

Part of the decision not to use the 01A was driven by RCA’s desire to promote their circuits.  With 2,000 patents, including Armstrong’s Superheterodyne and Regenerative designs, RCA could build circuits that other manufacturers simply did not own the rights to, designs that required tubes with the low inter-electrode capacitance of the 199.

neutrodyneBut the biggest obstacle standing between RCA and the production of an inexpensive three-dial TRF was a series of legal battles with a group of 14 firms,[4] known as the Independent Radio Manufacturers (IRM), who were licensed to produce Hazeltine-Neutrodyne receivers.  It was a feud initially fueled by RCA’s decision not to license other manufacturers to use the Armstrong regenerative circuits, then inflamed by one of their partners, the Wireless Specialty Apparatus Company (WSA).

The Radio Corporation of America was formed at the end of WWI to prevent foreign interests, i.e., Marconi, from dominating wireless communications in America.  At the urging of the U. S. Navy and President Woodrow Wilson, General Electric canceled the sale of Alexanderson alternators to the Marconi Company and formed a new American company whose primary purpose would be to checkmate Britain’s world-wide domination of all communications—cable and wireless.

To facilitate this goal, a complex series of cross-licensing agreements were made between the four primary patent-holders in the field: General Electric, Western Electric, Westinghouse, and United Fruit:

● G. E. owned the Alexanderson alternator patents as well as the interest (including the manufacturing facilities) of American Marconi.
● Western Electric owned rights to de Forest and Lowenstein vacuum tube patents.
● Westinghouse owned rights to the Fessenden Heterodyne and Armstrong "feedback” patents. 
● United Fruit acquired Wireless Specialty Apparatus in 1912.  Wireless Specialty Apparatus owned patents to the crystal detector while United Fruit owned 22 wireless installations around the globe.

"The original agreements between RCA, GE, and American Marconi granted RCA the rights to operate and maintain communications systems, market radio products and services, and develop new radio technologies—but specifically excluded RCA from manufacturing radio-related products.”[5]

"When the Radio Corporation realized that it could not operate without the Fessenden and Armstrong patents, Westinghouse was brought into the 'radio group' fold in June, 1921.  It contracted to produce 40% of the apparatus sold by the Radio Corporation while General Electric would make 60 percent ... if either company couldn't meet its quota, it could ask Wireless Specialty to manufacture for it ..."[6]

In June of 1922, Wireless Specialty threatened legal action against any other company making or selling crystal detectors.  “Freed-Eisemann went to court to enjoin Wireless Specialty from publishing these threats and to sue for damages; to aid in these suits it gathered a group of other New York crystal-set makers together in the Independent Radio Manufacturers Incorporated [IRM], retaining the prominent law firm of Pennie, Davis, Marvin and Edmunds [PDME].”[7] 

Through PDME they learned about Professor Louis Alan Hazeltine, who had come up with a means of stabilizing a tuned-radio-frequency amplifier.  Using Hazeltine’s notes, Freed built a prototype that worked beautifully.  Frank Andrea was the first to put a Neutrodyne set into production, the FADA 160A, but it was Freed-Eisemann who really made the most of things.  Sales of their first Neutrodyne, the NR-5, pushed their profits for 1923 one hundred times higher than those of 1922.[8]

So why did RCA finally build a TRF with 201As for their 1927 line?  With the superheterodynes at the top, the Radiola 20 in the middle, and the little regenerative Radiola IIIA still available at the bottom (till February of '27), they had a good share of the market.  The next model to follow, the AC operated Radiola 17, holds the answer.  The new AC-type-26 tubes in the 17 looked and performed just like 201As.  Inter-electrode capacitance and gain of the 26 was nearly identical to that of the 201A. If the newly-designed tuned circuits and variable capacitor assembly of the Radiola 16 worked with 201As, then they should work with the new AC 26 tubes.  A single-dial TRF with five 201A tubes and one 112A may have seemed trivial, almost a throw-away by 1927, but it paved the way for the Radiola 17, America’s first practical AC set designed to use AC tubes

Tube Type

Filament volts

Filament Amps









3.0 - 3.3

0.06 – 0.063

3.3 µµf





8.1 µµf





8.1 µµf


Unfortunately for RCA, the success of the 17 was short-lived.  In spite of their attempts to use distributed “space capacitance” to provide neutralizing feedback and avoid another day in court with Hazeltine, the 17 was unstable.  To make matters worse, Hazeltine filed suit against RCA in November of 1927 claiming infringement on patent number 1,533,858.  The case was tried in 1930 and decided in September of 1931.  Judge Woolsey of the U.S. District Court for the Southern District of New York held that two models, Radiola 16 and 17, infringed upon Hazeltine’s patent on plate circuit neutralization.[9] 

Louis Hazeltine

This was not the first time that RCA would lose in court to the Hazeltine Corporation, nor would it be the last.  The combination of PDME’s legal acumen, Professor Hazeltine’s electronic abilities, business sense, and an absolute gift for spotting and grooming young talent created a company that became the “principal competitor to RCA in making and licensing radio inventions.”[10]

The introduction of the screen-grid tube in 1929[11] made neutralizing circuits unnecessary and put an end to Hazeltine Corporation’s monopoly in that field.  But another Hazeltine employee, Harold Alden Wheeler, created an endless parade of innovation that would endure for the next forty years.  In 1925, he invented Automatic Volume Control, or AVC.  He designed the first broadcast receiver in which diode AVC was marketed, the Philco 95.  Diode AVC “became the keystone of the Company’s patent portfolio in the 1930s, from which royalties carried the Company through the Depression.”[12]

On September 27, 1932, Wheeler’s first three AVC patents were issued, “just days after the RCA labs had released a bulletin recommending diode AVC using their new tube type containing two diodes and a triode on one cathode. [type 55]  'When they saw my patent, it spoiled their whole day.'”[13]

In 1937, RCA finally succumbed and took out a license under the Hazeltine Corporation patents.

Harold Wheeler

In The Early Days of Wheeler and Hazeltine Corporation, Harold Wheeler states, “The phenomenon of Hazeltine Corporation before World War II could not happen again.  The practices of that day enabled the Company to thrive as an engineering organization supported entirely by patent royalties.  The technology of radio and television was simple enough for a small, independent group to contribute substantial innovation.  We made the most of that opportunity.”[14]

Copyright 2010 SNRaymer 



1.  Eric Wenaas, Radiola, The Golden Age of RCA (Chandler, Arizona: Sonoran Publishing, LLC, 2007), 172.
“RCA was obligated to sell radio equipment according to the 60% - 40% agreements with GE and Westinghouse, but since Westinghouse was well ahead of its quota for 1922, RCA had to favor GE in the 1923 season, independent of customer demand.  It is likely that the Radiola V and VI, which were no more than dressed up combinations of the thoroughly mundane 1300/1400/1520 receivers from the 1922 season were included in the 1923 lineup to help increase G. E. revenue share.”

2.  Gerald F. J. Tyne, Saga of the Vacuum Tube (Indianapolis, Indiana:  Howard W. Sams, & Co., Inc., 1977), 314.  “The UV201A, which was announced at the same time as the UV199 at the New York Radio Show in December 1922, had been designed to use a thoriated filament in the existing UV201 structure and to replace the UV201.  The electrode assembly of the UV201 was somewhat larger than that of the UV199, so manufacturing modifications were relatively simple.  Work on production procedures was started in Nela Park and Harrison in April 1922 and progressed rapidly.  In October 1922 manufacture of the 201 was discontinued and production of the 201A was initiated.  There were sufficient stocks of the UV201 on hand to meet demands for some months.  The UV201A sprang into instant popularity because it required only 0.25 ampere at 5 volts, one quarter of the filament power of the UV201.  By August 1923 it was sold more widely than any other tube.  Its life was satisfactory and production was free from trouble.”

3.  Ibid., 313. “The UV199 was introduced at the New York Radio Show in December 1922, but it was not available to customers until about the middle of April 1923.  Difficulties arose with this tube.  When it was used with three new dry cells, the available filament voltage was 4.5 volts.  If excess voltage was not absorbed, the thoriated filament was soon deactivated ... there was a tendency on the part of the listener to turn up the rheostat to get maximum output from the tube.  As a protective measure, the filament was lengthened to correspond to 3.3 volts.  These tubes could be operated with dry cells which had been in service until their voltage dropped to 1.1 volts – the end of their useful life.”

4.  Harold Alden Wheeler, The Early Days of Wheeler and Hazeltine Corporation (Poughkeepsie, N. Y.:  Hamilton Reproductions, Inc., 1982), 160. “Hazeltine’s patents on neutralization were licensed exclusively to IRM through the medium of Hazeltine Research Corporation (HRC).  The IRM grew to 14 members, then it was closed to further membership.

5.  Eric Wenaas, Radiola, The Golden Age of RCA, 29.

6. Alan Douglas, Radio Manufacturers of the 1920’s Volume 3 (Vestal, NY: Vestal Press, 1991), 7.

7.  Alan Douglas, Radio Manufacturers of the 1920’s Volume 2 (Vestal, NY: Vestal Press, 1991), 2.

8.  Ibid., 2. “Freed-Eisemann did rather well with its NR5: 1923 sales were four times the previous year’s, and net earnings (profits) 100 times higher.  The company moved into a new factory of 15,000 square feet in December, 1923, in the Sperry Building in Brooklyn, eventually occupying 50,000 square feet and employing as many as 570 workers.  It also brought suit against PDME [the law firm representing the IRM] and refused to pay royalties to Hazeltine, claiming that PDME’s lawyers were financially interested in the Hazeltine Corporation at the same time they were advising their client Freed-Eisemann to sign the royalty agreement.  Hazeltine in turn sued Freed-Eisemann for breach of contract.  Freed-Eisemann was hoping to have its royalties reduced, from 6% of the wholesale receiver price, to 6% of the neutralizing condenser alone, and offered Hazeltine $30,000 a year, but eventually lost, and grumpily went back to paying the whole amount.”

9.  Examination of Woolsey's official court ruling confirms Wheeler's claims about this case; see Hazeltine Corporation v. Radio Corporation of America (D.C.) 52 F.(2d) 504, accessed via Lexis Nexis, http://www.lexisnexis.com, January 1, 2010. Thanks to Shawn VanCour for his help in locating this document.

10.  Harold Alden Wheeler, The Early Days of Wheeler and Hazeltine Corporation, 190.

11. The AC-operated UY-224 was introduced in April of 1929.
The first screen-grid tube was the DC-filament, type 222 introduced in December of 1927, but not used by RCA until their model 21 in October of 1929.

12. Harold Alden Wheeler, The Early Days of Wheeler and Hazeltine Corporation, 198.

13.  Ibid,  206.

14.  Ibid,   407.
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Museum of Broadcasting