Tuesday, October 02, 2007

The Neutrodyne Radio

The Neutrodyne was a special kind of radio receiver that pre-dated the superheterodyne. they innovated a small antiphase signal from the addition of small windings on tuned anode coils. These neutralized the inter-electrode capacitance of the old triode tubes.

It's inventor, Louis Alan Hazeltine was born in 1886 in Morristown, NJ. He graduated from the Stevens Institute of Technology in 1906 and went off to Schenectady, NY for a job at General Electric. GE wasnt destioned to contain him and he returned to acedemia. In 1907 he went back to steven's to teach electrical engineering becoming department head 10 years later. In a collegiate enviornment he had time to do the research he wanted. He read up on research on vacuum-tube circuits and other innovations of Edwin H. Armstong. He wrote a text book and became a radio consultant to the U.S. Navy in 1918. More here.

The Hazeltine-Neutrodyne receivers all but ended the high-pitched squealing noises that were indigenous to AM radios of the era. More importantly it also ended the RCA dominace over the commercial radio industry. You might have assumed by now that this was a predecessor to the Superheterodyne but actually it was a low cost contemporary. The Neutrodyne was cheaper to build and cheaper to buy. More importantly it was easier to operate. it took more than 5 years for the price of vacuum tubes to drop enough to make the Superheterodyne practical domestically.
The circuit design made a comback in the 1950s in TV receivers. they were integrated into the RF amplifiers of tube VHF TV tuners to do the job 10 million Neutrodyne radios already did so well. He later advised the U.S. government on regulation of radio broadcasting, in somewhays setting the boundaries for the FCC for decades to come. During World War II he served on the National Defense Research Committee. Later in lafe that same clever bastard invented the Hazeltine-Fremodyne Superregenerative circuit reducing noise in even FM radios. he died May 24th, 1964.

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