To the Editor "QST."
In the various Armstrong circuits, is the increase in the strength of signals due entirely to the beat or heterodyne effert, or are there any other etfects noticeable which cause added response in the phones?
If there were another type of generator, for undamped waves, as efficient as the audion, and if the beat effect produced by the generator were utilized on an ordinary detector circuit as sensitive as the ordinary audion receiver circuit, would this circuit be as sensitive and satisfactory as an Armstrong circuit?
What is meant by "increase in audibility" — an amplifier concern claims to have an instrument that increases the audibility 1500 times. Does this mean that the sound wave produced has 1500 times the amplitude and what relation has it to the number of times the signal strength is increased?
(Signed) EDGAR FELIX,
New York City.
In the various Armstrong circuits, the increase in strength of signals is due to amplifying effect as in the ordinary amplifier rather than the heterodyne principle. Of course, in the Armstrong circuit, these two effects are combined, but the real increase is due to amplification.
It is the writer's opinion that another type of generator such as you mention would not he as efficient as fhe Armstrong circuit. This is due to the peculiar repeating action which is obtained between the inductance coils.
"Increase in audibility" means that the instruments amplifies a given sound a certain number of times when a given factor of loudness is taken as the audibility unit. That is, a certain strength of signal may be taken with an audibility of one, then the amplification or increase in signal strength is a given number times the audibility.
A more complete discussion of these questions will be found in Armstrong's article in "The Proceedings of The Institute of Radio Engineers," Volume 3. No. 3.
New York, Feb. 7, 1915.
My dear Mr. Tuska:
Allow me to thank you for your very courteous and carefully considered reply to my letter of the 22nd ult. 1), regarding Armstrong circuits.
Not only have yon answered my questions completely, but you have shown me the energy and seriousness of the work you have undertaken. I am sure that the American Radio Relay League is and will be a great and thorough success — imitation and rival leagues not with standing.
Thanking you again, I am
Most, sincerely yours,
(Signed) EDGAR FELIX.
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