Armstrong and Sarnoff, 101 Years Ago

by Don Tuite
Jan 30, 2014

On the 101th anniversary of the validation of Armstrong's regenerative receiver, (and the 41st since Armstrong's death), a radio museum in New Jersey recalls the event.

Sixty-one years ago, on January 31, 1954, Edwin Armstrong, who invented the regenerative, super regenerative, and superheterodyne detector circuits for continuous-wave and amplitude modulation and the whole art of frequency modulation broadcasting, killed himself by leaping from a window in his New York apartment.

Almost exactly 41 years earlier, Armstrong, accompanied by Professor Morecroft from Columbia University, demonstrated his regenerative receiver to David Sarnoff and Roy Weagant of The American Marconi Company at the Marconi Belmar receiving station.

Ultimately, Armstrong’s relationship with Sarnoff and RCA was, to say the least, adversarial, (See the Wikipedia bio above.) and many of my engineer friends blame Sarnoff for Armstrong’s suicide.

Nevertheless, the event 101 years ago, the validation of the regenerative detector was a significant inflection point in the history of communication.

Which takes us to, which is the on-line presence of the InfoAge Science History Museum and National Landmark, which happens to be the site of The American Marconi Belmar receiving station, which was later Camp Evens, a military base, then an RCA facility, and then an Army research facility. In other words, the place is steeped in the history of 20th century electronics engineering.

Okay, the date is a centennial-plus-one, but there are things happening to mark the date of the validation of Armstrong’s regenerative receiver circuit, and they’re not happening until next weekend. (It’s hard to compete with the SuperBowl.) If you’re in the New York/New Jersey area, you should check them out

Essentially, The New Jersey Antique Radio Club’s Radio Technology Museum at the site will host an observance of the occasion at the InfoAge Museum in Wall Township, NJ on February 8th and 9th from 1 to 5 PM.  There will be a display and demonstration of vintage regenerative radio receivers with a formal presentation at 3 PM.  The other InfoAge museums will be open as well.  Admission is free, but five-dollar donation to is suggested.

Working receivers on display will include a mock-up of Armstrong’s original circuit receiving a simulated spark radio-telegraph transmission and a WWI era naval receiver.  This receiver, a Wireless Speciality Apparatus Company IP-501, can be operated both as a crystal set (passive receiver) similar to the Marconi 101 and as an Armstrong regenerative set using a vacuum tube to provide amplification, and will give a feel for the receivers involved in the 1914 demonstration.

Even if you don’t go, take a look at the event Webpage.  It includes a replica of Sarnoff’s assessment of the demonstration, and given the events of the ensuing 40 years, and Armstrong’s ultimate posthumous patent victories, it’s a moving piece of tragic irony.

Also, if you morse code proficiency is good at around 20 words/minute, you can start now by going to Ustream and trying yourself out on a test video:

What you will see on the video is a 1918 IP-501 receiver operating in the Armstrong

regenerative mode, with an audio track emulating the same signals from the Salby-Arco

alternator in Nauen, Germany that Armstrong and Sarnoff heard 101 years ago.

Discuss this Blog Entry 2

on Feb 5, 2014

It is saddening that a great mind can be provoked to suicide over an incessant quarrel over intellectual property, capped with a deprivation with the one you love dearly (just when he needed it most). It must have been a very harsh ordeal.

But this won't overshadow my new-found admiration for Mr. Edwin Armstrong. Visiting the webpage of InfoAge, I learned a whole lot more trivia about him which was nothing short of ingenious.

on Feb 10, 2014

That's an interesting story about the supposed influence of Sarnoff on Armstrong. It reminds me of the theme of the "Amadeus" movie in which a jealous Salieri provokes Mozart to death. Mr. Sarnoff was definitely a very hard-driving goal-oriented capitalist. I seem to recall that he's responsible for the strange words "Licensed only to the extent indicated on carton" on all vacuum tube boxes.

But if we're going to talk regenerative receivers, we should mention professor Hazeltine, inventor and promoter of the "FADA Neutrodyne" receiver, who hated regenerative sets with a passion, even more than he hated sparking trolley wires, dirty transmission line insulators, and the housewife with her electric washing machine ("a radio bugaboo"), because all of them produce noises which "disturb the serenity" of radio listeners. Regenerative radios have a propensity to become RF oscillators with antennae attached.

Professor Hazeltine can be forgiven for not inventing the superheterodyne system, but his "neutrodyne" TRF receiver was the second best devised. The "neutrodons" were variable capacitors in the picofarad range that coupled an out-of-phase version of the plate voltage back into the grid. They were to be adjusted so as to exactly cancel out the Miller capacitance. They boosted the gain of each RF stage without any risk of oscillation.

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