What Everyone Should Know About Radio History Part II

During 1911 and 1912 E.H. Armstrong was studying for the degree of Electrical Engineer at Columbia University; he was not an especially brilliant student, in fact in many of his courses he did rather poorly. The writer knows because Armstrone was on of his students. The characteristics of alternating current machinery in general, did not prove very enticing to the young student, not because he was lazy or indifferent but because he had a hobby - and a vision. He was experimenting at his home with wireless apparatus and trying to find out how the three electrode audion of De Forest worked. If De Forest confessed in public that the action was too mysterious for him to explain, then Armstrong would explain it to him! Which he promised to do, and did very shortly.

After graduating, Armstrong continued at Columbia as assistant to the writer in the radio laboratory; later he worked with Prof. M. I. Pupin, continuing his study of the three electrode tube. As the writer looks back to those days it seems undoubtedly true that Armstrong understood the action of the audion better than anyone else in the world. Day and night he thought and talked of nothing but the audion; his devotion to this study, and perseverance therin finally brought rich reward - he was granted a patent, the validity of which was recently confirmed, which gives to him credit for being the first really to understand the action of the three electrode tube.

In using the audion as a detector of wireless signals certain coils were required, and Armstrong accidentally placed two of these coils much nearer to each other than they should normally be and lo - a strange noise was heard in the telephones. This strange noise started Armstrong to work on his wonderful discoveries.

It was noted in the first part of this history that the more or less accidental occurrence of a small spark started Hertz on his epoch making discoveries, and certainly it was as much an accident that led to Armstrong's work. But by those who may, at this point, think that an accident may some day make them also famous, let it be remembered that after the accidental noting of something unusual it was a long and difficult road which led to the complete explanation and utilization of the phenomenon involved.

The noise which Armstrong heard was the beat note between the oscillation being set up by the De Forest audion he was using and a signal being sent out from some continuous wave station. He found that the pitch of the note varied with the adjustment of his circuit, and by keen intuition he came to the conculusion that the tube he was using was oscillating at a high frequency. He pursued the study of the action until it became very clear to him and he made patent application for his idea - which is fundamentally this: If the plate circuit of a three electrode tube and the grid circuit are suitably connected (by magnetic induction or otherwise) the reactions occuring between the two circuits tend to set up alternating current in that circuit which has a condenser and coil connected together, the value of inductance and capacity determining the frequency of the alternating current generated.

He found out that even if the adjustment was not sufficiently carried out to make the tube oscillate, still the interconnection of the plate and grid circuits might cause a tremendous increase in signal strength. This is the "feed-back" or regenerative idea for which Armstrong's work is known.

Since Armstrong's first work appeared, innumerable circuits, with fancy names sometimes attached, have been published, the "inventor" probably thinking many times that the idea was entirely new. They all are embraced by Armstrong's patent, however, if they function by the interaction of the plate and grid circuits of the tube which can be brought about by the use of various connections of condensers and coils. In general there must be made provision for the energy which is resident in the plate circuit battery to get into the grid circuit if oscillations are to be maintained; if this provision involves the electrical or magnetic interconnection of the plate and grid circuits by use of condensers and coils suitably arranged, the idea comes under Armstrong's feedback claims. It is of course possible, that some other action may be found by which case the present monoply on the use of regeneration would be temporarily broken.

It seems a simple thing to couple together the plate and grid circuits of a vacuum tube and one would scarcely believe the importance of such an evident possibility. The results of the coupling are however very important. When a continuous wave signal is received the ordinary crystal detector or vacuum tube detector does not yield a signal because there is no variation in the amplitude of the high frequency current, a variation with a frequency in the audible range. If, however, the local circuit is continually excited by a high frequency current, when the high frequency signal is received the two high frequencies will act together and produce "beats," and the frequency of these beats is the same as the difference in frequncy of the two different currents. This method, as mentioned previously, is the result of Fessenden's work.

Armstrong's idea evidently enables the vacuum tube which is being used as a detector to act also as a generator of the high frequency currents which serve to produce the beats when the continuous wave signals arrive. Not only does this simple coupling idea of Armostrong thus permit the audion to act as a receiver of continuous wave signals, but it also makes it an extremely sensitive receiver at the same time, if the adjustments are carefully carried out. The writer well remembers one night, before Armstrong had published his explanation of the action of the oscillating tube, spent at the Marconi's then new station at Belmar, NJ. Mr. Weagant, the chief engineer of the American Marconi Company, and Mr. Sarnoff, at present manager of the Radio Corporation, were also witnesses of those early tests when Armstrong showed us how his circuits could "pick up" the continuous wave stations of the Pacific coast - stations with only a few kilowatts of power. To hear the note of the station changed at will, by a turn of a handle on one of the boxes, was a severe puzzle for the Marconi engineer, especially as Armstrong, like a proper inventor, had everything completely hidden in boxes, with the lids securely screwed down. And nary a chance did the chief engineer have to peep inside! He would surely have been surprised to see how simple the whole thing was.

As another illustration of the remarkable advance in sensitiveness made possible by Armstrong's invention, the writer recalls hearing in his laboratory at Columbia, on several occasions, a station on our west coast in communication with one at Honolulu, and the two stations were continually calling for "repeats". They were only 2,000 miles apart, over the ocean, and the laboratory was 3,000 miles over land from the nearer one and 5,000 miles from the farther. Both stations were received at the laboratory clearly by using Armstrong's apparatus, yet they could not understand each other, using the receiving apparatus then in general use.

Besides the wonderful amplification of signal obtainable by the feed-back principle, the selectivity of a circuit is greatly improved so that stations sending on nearly the same wave length cause no interference. This idea is of more value in telegraphy than in telephony; in the latter the receiving circuit must not be too selective or else the speech will not be clear but will be drummy in quality, and indistinct.

Armstrong has also given to us a valuable idea in his special short wave amplifier, and has just startled the radio world with what he has named his "super-regenerative" scheme wherein the present amplifying power of his circuit is greatly increased.

This article was published more than one hundred years ago. The section reproduced above concerns the early productive years of Edwin Armstrong, the inventor of frequency modulation, one of the most important technical breakthroughs of all time, useful for much more than broadcasting FM stereo music (the concept of "stereo" didn't exist when Armstrong invented FM).

This article shows that well before he invented FM, Armstrong was already the source of important breakthroughs in radio technology, which at the time was as new as quantum computing is today.

I learned today that the rotating-head video tape recorder, later to become the VCR, wouldn't have been possible if not for frequency modulation, for reasons that are subtle but also vital.

I greatly admire Edwin Armstrong, although he came to a tragic end.

When the author refers to the “audion,” he is using the word that Lee De Forest used to describe his invention, which later was called the “vacuum triode,” or simply “triode.”

At the time this article was written, the word “triode” had not yet been coined.

Between the regenerative and superheterodyne receivers and FM, Armstrong’s inventions had greater impact than any other and likely will never be equaled.

This article shows that well before he invented FM, Armstrong was already the source of important breakthroughs in radio technology, which at the time was as new as quantum computing is today.

While many households today do not even have one FM radio (2020 survey find 68% of all Americans have at least one radio in their home), we have been given a few over the years, and I use an old laptop with about 20,000 evangelical sermons and songs which broadcasts to the household 24/7 - with no commercials - over a cheap USB powered (legal 0.5 watt) FM transmitter at 87.5 (empty spot, which some radios do not go to, since FM broadcast in the United States starts at 88.0 MHz and ends at 108.0 MHz. Works quite well on the same floor, and outside to about 50 feet to a portable radio. Praise God.

“While many households today do not even have one FM radio (2020 survey find 68% of all Americans have at least one radio in their home)”

Wow, I find this shocking enough that I don’t believe this statistic.

a lot of phones have built in fm tuners that will work without cel service (at least mine do)

a lot of people have stereo systems or mini systems which probably have fm and am.

some people might even have cars which have fm tuners.

a lot of people might even listen to sports on a transistor radio.

maybe I just am biased cause I bought my first radio when I was around 6 or 7

I highly recommend this incredible, encyclopedic site covering every aspect of the history of radio technology and the business that grew up around it. You could spend the rest of your life browsing those pages and never see all of it.

https://www.worldradiohistory.com/index.htm

Radio is a sound salvation
Radio is cleaning up the nation
They say you better listen to the voice of reason
But they don’t give you any choice ‘cause they think that it’s treason
So you had better do as you are told
You better listen to the radio

Long time lover of the spark gap here. Have probably averaged close to 5 hours a day for 50 + years. All genres. Amateur, SWL, talk, old time entertainment. Even npr! One eyed pagan nearly never. Some radio of course now podcast etc.

The old mystery of the ether will be with me to my grave—no truer or loyal friend that rates second only in companionship to my wife and no others.
Cheers

Without the Fleming Valve, the Audion would never have existed. And without the Edison incandescent bulb, the Fleming Valve would never have existed.

I was just out in th acreage this afternoon making contacts with Japan, Ankorage, Idaho, Arizona and I decided to pack things up before I could log Austrailia in the logbook.

I was using a little Xiegu G-90 20watt transceiver with about 17 and a half feet of speaker wire run up a squib pole and six 1`7 foot radials on the ground.

Nice way to spend the afternoon here in the Gold Country of California. Japan is always a good bet in the afternoon and those cats are always good for the log book. They are a bit shocked when I tell them its just 20 watts and a bit of speaker wire....oh—did I neglect to mention the 4:1 balun? That is whay makes it all work.

Worked mostly 12m and 17m. Amazing—considering how it all began...

I often think of Armstrong, les paul and schockly. All brilliant. Two died in misery and one died happy. Two fought the system and one kept going to Gibson until they finally saw the light.

The cell phones have an FM receiver.
My stereo system has an FM receiver.
The car has AM and FM reception (and satellite).
I have several old Watchman pocket TV sets that do both AM (picture) and FM (audio). I also have a setup in the basement to generate the old NTSC signals. The TVs still work just fine.
Have a VHS tape recorder/player and cassette deck connected to the living room TV and stereo.

I’m a dinosaur.

Interesting article. I got interested in HAM radio recently. Passed my Technician, General and Extra licenses in the last month.

I have a QRP (low power) transceiver coming (https://www.ebay.com/itm/235128617053). Have to set up my antenna and some other things. Looking forward to making my first DX connection.

17 posted on 03/09/2024 7:10:09 PM PST by E. Pluribus Unum (The worst thing about censorship is █████ ██ ████ ████████ █ ███████ ████. FJB.)

The old mystery of the ether will be with me to my grave—no truer or loyal friend that rates second only in companionship to my wife and no others.
Cheers

When I was young I spent hour after hour in front of our radio console to catch the next episode of my favorite radio show.

Now I spend my time in my Amateur Radio "Ham Shack" with my wife who is also licensed. Some things never change.

While many households today do not even have one FM radio (2020 survey find 68% of all Americans have at least one radio in their home)....

I never listen to radio in my house and I don't have any AM or FM radios inside my house. The closest is the one in my car in the garage. Driving is the only time I listen to radio. I could stream radio through my computer, but never do.

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