3.4 - Pathfinders of the modern radio receivers
Edwin Howard Armstrong




Among the main names related with the improvement of the modern radio receivers are:

Earnest Humphrey Scott, pioneer in the production of state of art receivers;

Edwin Howard Armstrong, inventor of the three main types of circuits: regenerative, superheterodyne and frequency modulation.





Louis Alan Hazeltine
Louis Alan Hazeltine. Professor of Stevens Institute of Technology, USA, developed the neutrodyne circuit. Hazeltine theory led largely to lifiting the thermionic valve amplifier out of the realm of experimentation and into the realm of calculable engineering.
In the neutrodyne circuit both tuned radio frequency and audio amplification has a kind of stabilizers, known as “neutrodons” by mean of which the circuit is balanced out, or neutralize the nowls caused by the valve's oscillation.
In the chaotic time in the twenties when broadcast listners were beset by howls the neutrodyne circuit was a great success and Hazeltine has been considered as an inventor whose main tools were the pen and the slide rule, tooking the squeks and howls out of the radio receiver.
The term "neutrodyne" was coined by Willis H.Taylor, Jr. a participante of the Pennie-Davis-Marvin-Edmond associated attorneys an office specialized in patents. Originally the term was used by the independente group of radio manufacturers to find a solution for patent litigation based in the Hazeltine's work.In the beginning the independent group of radio manufacturers basically comprises: F.A.D. Andrea, (FADA), Freed-Eisemann and Garod.The term "Neutrodyne" was used as a trademark as soon as the first radio receivers were launched in the market by FADA in 1923.