Hazeltine Corporation
450 East Pulaski Road, Greenlawn, NY 11740, U.S.A.

Hazeltine Corporation was a defense electronics company.

The company was founded in 1924 by investors to exploit the Neutrodyne patent of Dr. Louis Alan Hazeltine.

Headquartered in Greenlawn, Long Island, New York, since 1955, it had facilities in several other locations in Long Island, including its Wheeler Laboratories facility in Smithtown, NY and manufacturing plants in Riverhead and Little Neck, NY.

The company concentrated originally on the design of electronic circuits and the licensing of patents. Innovations in radio, monochrome and later color television components allowed the company to grow. One particularly lucrative design was the AGC (Automatic Gain Control) circuit. This was such a useful feature that almost every AM radio made used this feature, "by license from Hazeltine", from about 1930 until the patent expired.

Until the invention of the tetrode (4 element vacuum tube) in 1926, all radios used triode (three element) tubes. The problem with triodes is that the strong signal from the tube’s plate, which is the output element, can couple back into the tube’s grid, which is its input element. This can result in an unwanted feedback, similar in principle to placing a microphone too close to a loudspeaker in a public address system. It would result in the radio occasionally breaking into a howling squeal. As a result, manufacturers had to operate the tubes at less than optimum gain to prevent this feedback, reducing the sensitivity of the radio. In 1922, Hazeltine developed a method to cancel out, or “neutralize,” this unwanted feedback, allowing the tubes to be operated with much higher gain. Some sources attribute the development to Harold Wheeler, who worked under Hazeltine in his lab at the Stevens Institute, but Hazeltine was granted a patent for the invention, which he named the “Neutrodyne” circuit. A prototype of the Neutrodyne receiver was presented at a meeting of the Radio Society of America at Columbia University in 1923.

The Neutrodyne circuit was popular in radio receivers until the 1930s, when it was superseded by the superheterodyne receiver.

In 1927, the tetrode tube hit the market. Its design placed a shield element between the tube’s grid and plate, blocking the unintended feedback path. It rendered the need for the Neutrodyne circuit obsolete, but by then more than 10 million radios using it had been produced, earning an estimated $3 million in royalties for the Hazeltine Corporation.

Louis Alan Hazeltine passed away in 1964 at age 78. He had 36 patents in his name. In the 1970s, the corporation briefly produced a line of monochrome computer terminals. The Hazeltine Corporation remained a defense contractor on and off until 1986, when they were acquired by the Emerson Electric Corporation. Emerson sold off its defense business in 1996. In a deal said to be worth $110 million, the company was bought by GEC-Marconi Electronic systems, a General Electric subsidiary, and renamed GEC-Marconi Hazeltine. In 1999, the company merged with British Aerospace to form BAE Systems, marking an end to the commercial use of the Hazeltine name.