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RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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September 1930 Radio-Craft[Table of Contents]
People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Radio-Craft was published from 1929 through 1953. All copyrights are hereby acknowledged. See all articles from Radio-Craft.
Superheterodyne receivers were originally the sole domain of the Radio Corporation of America (RCA), which owned the patents and refused to license them until around 1930. Hugo Gernsback, a contemporary editor of the era, provides a little insight into the superregenerative receiver (an Edwin Armstrong invention in 1912) circuits superheterodyne was about to replace, and why it was an important improvement in technology.
Sidebar: The question often arises regarding the difference between a 'heterodyne' circuit and a 'superheterodyne' circuit. The most popular answer that 'super' (meaning 'over') refers to the intermediate frequency (IF) being located above the range of human hearing, which peaks at about 15 kHz. Doing so assured that any IF leakage into the audio circuits would not be discernable by the radio listener.
By Hugo Gernsback
Radio, as I have said often before, is known to go through certain evolutionary cycles. It has done so from the start, and it can be expected to go on indefinitely in this manner. The radio industry has always been progressive enough to take hold of that instrumentality which it thought would give the best results. It was so, beginning with the coherer-spark-gap cycle; it was so during the crystal-detector cycle, the regenerative "blooper" cycle and, of late, in the so-called tuned-radio-frequency cycle.
Practically all sets in use today use some sort of tuned-radio-frequency circuit, or a modification of the principle. Regeneration has been severely left alone; because in the modern set, the old shrieking and whistling has been completely tabooed by radio engineers and the quiet set is the order of the day. During the last few years, few changes in the average radio set have been noted and, while we have changed our tubes from the old-fashioned "triodes" to "screen-grids," the circuits still remain fundamentally the same.
The superheterodyne cycle, into which we are now about to be launched, promises to change radio conditions enormously. It is true that the superheterodyne has been known for many years, and has been valued as one of the best and most sensitive circuits known. It has been, however, because of basic patents, the sole property of the Radio Corporation. This company steadfastly refused to license anyone else to use the superheterodyne patents until, very recently, the announcement was made that the R.C.A. will now license a number of companies to build superheterodynes for themselves.
This announcement is an important one and, in a way, it has created a sensation in the radio industry; particularly as the announcement of the decision was made so late in the season that it probably will affect few of the models that will come out during the remainder of 1930.
During 1931, however, the situation will be vastly different. There is not the slightest doubt in our minds, that practically every radio set manufacturer will immediately turn to superheterodynes, for a number of reasons. In the first place, there is no question but that the superheterodyne circuit is the best and most efficient circuit known to the radio art today. If one or two radio set manufacturers start to bring out superheterodynes, the rest of the industry must of necessity follow, or be left behind.
Of course, we will have many new variations of the superheterodyne and we may confidently expect that, if the entire radio industry is to stand behind the circuit, it will be greatly improved as time goes on. We will have screen-grid superheterodynes; we will have pentode superheterodynes; we will have all sorts of combinations of the circuit or adaptations of it; and there is little doubt that even the still more mysterious superregenerative circuit will also, in the near future, be heard from.
In the past, there was one slight disadvantage in using a superheterodyne set, and that was the necessity of using two tuning controls. The modern radio set buyer demands a single tuning control; and the R.C.A. has finally produced one good model in which a single tuning control is used. There is no question in our minds that the standard commercial superheterodyne set, which will be put out by the radio industry during the coming year, is to be of the single-control variety.
Of course, one of the various advantages of the superheterodyne is that it requires no aerial. Under modern conditions, with a broadcasting system of the power we have today, much better reception can be obtained by means of a superheterodyne than with practically any other set. The reason is, that the superheterodyne tunes much sharper, and it is much easier to tune out an interfering station with a loop than with a set that uses an aerial.
The sales arguments, when recommending a superheterodyne to the prospective customer, are of course much stronger; because he need incur neither expense or worry about an aerial. Then there are still in this world some people who think of an aerial as a lightning danger; these people will naturally prefer a superheterodyne, which has no "aerial complex."
We, personally, welcome the idea that the superheterodyne is now to come into its own. We urge every reader of Radio-Craft to brush-up on superheterodyne literature; and Radio-Craft, during the coming months, will do its share by publishing every month superheterodyne data which in time will be most valuable, not only to the general reader, but to the Service Man, the radiotrician and the professional radio man as well.
It is certain that the superheterodyne will stimulate the radio trade to a marked extent during the next few years.
It will have a great and lasting effect on automotive radio; as the superheterodyne is certainly a most efficient set for use in a car.
The superheterodyne will also encourage the long-neglected radio experimenter; who will again be able, we hope, to buy low-priced kits for experimental purposes.
From whatever angle you look at the situation, the superheterodyne cycle looks distinctly hopeful for the radio industry during the next few years.
September 28, 2015