Stevens Celebrates Coveted IEEE Milestone Recognition for Neutrodyne Radio Circuit

Century-old invention by Stevens Professor Louis Alan Hazeltine revolutionized early radio industry

A little over a century ago, radios were primitive, expensive and difficult to operate due to constant signal interference. Through 1922, these constraints limited the audience to approximately 10 percent of the U.S. population.

Enter Stevens professor Louis Alan Hazeltine, affectionately known as "Hazy." Sixteen years after graduating from Stevens in 1906 - by then the head of the Department of Electrical Engineering - Hazeltine developed a world-changing solution to both the affordability and listenability of radio: the neutrodyne circuit.

This invention recently earned Stevens a prestigious IEEE Milestone from the North Jersey Chapter of the Institute of Electrical and Electronics Engineers. A dedication ceremony was held on Oct. 19, 2024 in the Gateway Academic Center North Building.

The dedication ceremony attracted more than 100 distinguished guests, including Stevens president Nariman Farvardin and Jean Zu, Lore E. Feiler Dean of the Schaefer School of Engineering and Science, both of whom provided remarks about the neutrodyne's importance to Stevens' legacy.

Additionally, many IEEE members traveled to Hoboken, including Hong Zhao, chair of the IEEE North Jersey Section; Bala Prasanna, director of IEEE Region I; Kit August, former Bell Labs scientist and lead proposer of the Milestone; and Robert A Dent., a 1966 Stevens graduate and former IEEE chair. The event was emceed by Victor Lawrence, an IEEE fellow and a senior research scientist in Stevens' Department of Electrical and Computer Engineering.

This dedication was a long time in the making as the COVID-19 pandemic postponed the original ceremony years ago. But it was important to get everyone together to celebrate the neutrodyne's impact within the larger electrical engineering community.

"This is a major milestone. Very few institutions have received this honor," said Lawrence. "It's something Stevens should be very proud of and something they should promote prominently in the future."

The neutrodyne circuit in historical context

Stevens is one of only 13 schools in the U.S. to be recognized with an IEEE Milestone. While radio may seem primitive today, it changed almost every aspect of American life a century ago. Citizens received breaking news as it happened instead of waiting for the next day's newspaper. People became more politically knowledgeable and engaged with what was happening in their communities. Sports became more accessible to the masses. And people were exposed to music and arts they otherwise may not have been. This all stemmed from Hazeltine's breakthrough invention.

The problem Hazeltine addressed was that early tune-radio frequency receivers were difficult to operate as each circuit needed to be tuned to the same frequency and would oscillate and create interference that marred the listening experience. Therefore, only skilled operators tended to own radios.

Hazeltine conceived the neutrodyne while performing radio operations for the U.S. Navy during World War I and sketched it on paper as something to pursue later. Through trial and error with the original design, the neutrodyne came to life in the old Navy Building at Stevens in Hazeltine's lab with fellow professor Harold A. Wheeler and others.

Hazeltine and his team designed a circuit with a symmetric number of coils at a 54.57-degree angle. The magnetic coupling effect of the precisely angled coils eliminated oscillation and drastically improved sound quality.

The fruits of this labor resulted in licensing the neutrodyne to 20 radio manufacturers. Hazeltine sold an estimated 10 million circuits, leading to a massive spike in radio ownership from 10 percent of the nation in 1923 to 60 percent by 1927.

Louis Hazeltine's son, Barrett, attended and spoke during the dedication ceremony.Jeff Vock

Ceremony attendees got to see an exhibit of the neutrodyne and other Hazeltine-related items - he received 36 U.S. patents in his life - courtesy of Michael Molnar. Molnar, a project engineer for Diagnostic Services, is an avid historian who operates a museum featuring old radio and early television artifacts.

"As an amateur technology historian and radio TV collector, I enjoyed being part of the event as I felt a connection to the history of Hazeltine and the neutrodyne," said Molnar. "My memory of the old Navy Building is still vivid although it goes back 50 years. Now a plaque will stand there as a marker on the site and perhaps make it just a bit special to others."

A Family Affair

A highlight of the ceremony was Barrett Hazeltine's presentation about the family legacy. Barrett is Louis' son and professor emeritus at Brown University. Additionally, Barrett was a longtime member of Stevens' Board of Trustees. Barrett's son and Louis' grandson, Michael, a 1980 Stevens graduate, was also in attendance.

"It was very gratifying to be able to see the family honored by so many," said Lawrence. "They have contributed to so much of the history here and everyone was very excited to see them and talk to them on such a special occasion."

The ceremony closed with a presentation of the IEEE Milestone plaque. The plaque will be placed prominently on campus, though the final location is not yet determined.