The circuit was developed in the early 1920's by Alan Hazeltine and made by a group of more than 20 firms that were licensed to produce Hazeltine-Neutrodyne receivers known as the Independent Radio Manufacturers. Hazeltine's invention effectively neutralized the high-pitched squeals that had plagued early radio sets. The design also neutralized the stranglehold that RCA then held on the commercial radio industry. Compared to the technically superior Superheterodyne the Neutrodyne was cheaper to build and operate, and much easier for non-technical owners to use.
To properly set up a Neutrodyne receiver, not only did the circuitry need to be aligned for peak performance, (that is, getting all its tuned circuts operating "in step"), it also had to be neutralized. However, this procedure only needed to be done once (albeit by a serviceman) and thereafter the radio could be tuned by anyone without special skill, a unique feature at the time. The neutrodyne was the first commercial receiver suited to use by the general public. By 1927 some ten million of these receivers had been sold to consumers in North America.
By the 1930s, advances in vacuum tube manufacturing finally made Edwin Armstrong's Superheterodyne design practical for domestic receivers. Ironically, these same advances made it also possible to build superior TRF receivers that did not need neutralization, but since an even more superior superheterodyne could be made for about the same cost, the TRF technique fell into disuse.
To neutralize a Neutrodyne receiver the procedure went something like this:
It is important to neutralize using the actual tube that will be in that socket as grid-plate capacitance varies some from tube to tube. Also once neutralized the tubes should not be exchanged between sockets. Often replacing a defective tube with a new one required neutralizing the receiver again (therefore tube replacement usually required a serviceman).