Milestone-Proposal talk:Neutrodyne Circuit, 1922

Revision as of 16:29, 26 September 2019 by Allisonmarsh (talk | contribs) (support, with slight word changes -- ~~~~: new section)

Advocates and reviewers will post their comments below. In addition, any IEEE member can sign in with their ETHW login (different from IEEE Single Sign On) and comment on the milestone proposal's accuracy or completeness as a form of public review.

Milestone Proposal - Neutrodyne Circuit -- Jbart64 (talk) 17:44, 23 May 2019 (UTC)

I fully support this Milestone but the wording needs editing. I would indicate the circuit was developed on this site rather than assigning credit to Hazeltine. The circuit was actually developed by Harold Wheeler in Hazeltine's laboratory at Stevens Institute. So, although Hazeltine is usually named as the developer, the accomplishment is not strictly his. Milestones should avoid personal identification in favor of recognizing the general achievement. My suggested version of the Milestone is shown below.

The Neutrodyne Circuit was invented on this site in 1922. It used neutralizing capacitors to eliminate squeals and other noise that plagued earlier tuned-radio-frequency (TRF) receivers. The circuit made radios easier to tune and improved the clarity of reception; facilitating broader use by the general public, enabling new manufacturers to develop different products, and helping to grow radio the industry from amateur radio operators into a mass consumer market. Dave Bart

Updated Milestone Text -- Jbart64 (talk) 19:46, 16 September 2019 (UTC)

I understand the following updated text for the plaque will be posted. I concur with these revisions after consultation with the proposer. Dave Bart, Advocate

Revised Text: The Neutrodyne Circuit invented on this site in 1922 used neutralizing capacitors to eliminate squeals from parasitic oscillation that plagued early radios. Improved clarity of reception and easier tuning facilitated broader radio adoption by the general public. Multiple manufacturers licensed the circuit to make affordable consumer products, expanding the marketplace from amateur radio operators into a mass consumer market for news, information, music and culture.

Expert Letter #1 -- Jbart64 (talk) 19:59, 16 September 2019 (UTC)

To: Julia & David Bart <> Re: Neutrodyne Circuit Invention at Stevens Institute From: James Kreuzer <> 9/16/2019 2:37 PM (10 minutes ago)


To: IEEE Milestone Committee September 19, 2019

I have been the Librarian and Assistant Curator for the Antique Wireless Association (AWA) for the past 10 years. I have been a rare book dealer for 35 years and a wireless historian since 1975. I have written numerous historical articles for the AWA Journal and AWA Review throughout the years.

I have examined the Milestone Proposal for the Neutrodyne Circuit, 1922 and completely support the recognition of a circuit that has had a profound historical significance for American communications at the dawn of the broadcast era.

At the AWA Museum, we have been given the honor to preserve many receivers and components relating to the original Neutrodyne circuit, and I personally have built and have helped troubleshoot many receivers employing this circuit. Without the invention of this circuit, the development of the broadcasting industry would have been delayed, as the receivers that employed the existing regenerative circuit were difficult to use. In addition, replacement circuits were regularly needed to keep up with the rapid developments of newly designed broadcast transmitters. Thus, prior to the Neutrodyne Circuit, the audience for radio largely comprised amateurs, or technical hobbyists who possessed a specialized understanding of radio operations.

The Neutrodyne Circuit opened the door to licensing a generalized, standard circuit to manufacturers who then developed a range of radio products at reduced costs for the general public. This enabled the rapid expansion of radio beginning in the early/mid-1920s into a mass consumer marketplace. Although other factors also aided this product expansion and the growth in consumer demand, the Neutrodyne Circuit is widely credited as the key technical driver of this change.

I believe that it is entirely fitting as we near the 100th anniversary of this momentous achievement that the IEEE would choose to honor the Neutodyne Circuit with their Milestone Award.

I fully support the milestone proposal and the wording of the claim is accurate.

Best Regards, James Kreuzer N2GHD

Expert Letter #2 -- Jbart64 (talk) 04:24, 17 September 2019 (UTC)

To: Julia & David Bart <> From: Mike Molnar <> Monday, September 16, 2019 10:12 PM (1 hour ago) RE: FYI - Neutrodyne

Michael Molnar 134 Observatory Rd. Glen Gardner, NJ 08826 September 16, 2019

To the IEEE Milestone Committee:

I am a radio historian with the Antique Wireless Association and have published many articles on topics involving radio history. I reviewed the Milestone proposal and its supporting documentation, and I performed additional reading about the Neutrodyne Circuit.

I strongly support honoring the invention of the “Neutrodyne Circuit” with an IEEE milestone. I have previously researched this period of radio history in great detail, and I have attached a copy of the article I wrote for the AWA Review: “Hazeltine, the Neutrodyne and the Hazeltine Corporation”, AWA Review, 2013, Vol. 26, p. 3-20. The importance of this invention is clear for a number of reasons.

First, Hazeltine’s approach of using a mathematical analysis of the problem caused by capacitive coupling between elements of the triode vacuum tube, made a solution to the problem, neutralizing the effect of the capacitance, clear to him. This approach was unusual since, at the time, much engineering was still accomplished by “cut and try” design.

Second, as a result of this design, there was an important advance in radio operation. The early regenerative sets available from the beginning of broadcast radio were not user friendly. The settings used one day could produce squeals and howls the next. The Neutrodyne set owner could log the settings for a desired station and use those settings again and again. By taking away the need for operator expertise, the radio became a more acceptable home appliance.

Third, the Neutrodyne was a product available to new manufacturers outside of the RCA radio group. The resulting Hazeltine Corporation provided a healthy competition in the radio business and was responsible for many future developments. The company’s roots still exist today in the descendant lineage of BAE Systems.

I can also claim, from personal experience, that I have often experienced the difference when operating the Neutrodyne versus earlier regenerative sets. The ease of operation of the Neutrodyne is instantly clear. These radio sets were the best available for several years until the development of the “Screen Grid” tubes, tetrodes and pentodes, which did not suffer from the capacitive coupling problem.

Based on my research, I found that in 1923, on the site of the old “Navy Building” at Stevens Institute, Professor Louis Alan Hazeltine introduced two inventions that changed the design of radio receivers. By his mathematical analysis of capacitive coupling in triode vacuum tubes and magnetic coupling of RF coils, he was able to create a design that provided the general public a simple and reliable radio. These “Neutrodyne” radios were the best available in the mid-1920s.

In conclusion, I found the proposal accurate, and I fully support the milestone. It is well documented, and the achievements deserve recognition.

Mike Molnar

support, with slight word changes -- Allisonmarsh (talk) 16:29, 26 September 2019 (UTC)

I support this milestone & applaud the proposers for writing a citation that honors the technical achievement, not the inventor.

That being said, I think the second sentence is a bit cumbersome. I would suggest the following:

The Neutrodyne Circuit, invented on this site in 1922, used neutralizing capacitors to eliminate squeals from parasitic oscillation that plagued early radios. The circuit improved clarity of reception and made tuning easier, resulting in broader radio adoption by the general public. Multiple manufacturers licensed the circuit to make affordable consumer products, expanding the marketplace from amateur radio operators into a mass consumer market for news, information, music, and culture.