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Inventors of Radio - Thomas A. Edison
April 1960 Radio-Electronics

April 1960 Radio-Electronics

April 1960 Radio-Electronics Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

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Thomas Edison Patent #465,971, "Means for Transmitting Signals Electrically." Note the unlike Fig. 2, the full drawing includes ships at sea.

Upsetters of apple carts, rockers of boats, makers of waves, creators of stirs. All idiomatically describe actions of those who commit the transgression of challenging accepted norms. There is always someone claiming to have discovered the "truth" about one subject or another. In the world of technology, most often the object of contestation is which person was the "first" to have discovered, written, or performed something. Here in this 1960 issue of Radio-Electronics magazine, Mr. Leslie asserts that Thomas Alva Edison actually made the world's first radio broadcast, not Guglielmo Marconi. For some reason the image of Edison's "Means for Transmitting Signals Electrically" patent omitted the ships at sea overtop of the antenna structures, which seem to me to be critical in portraying the "wireless" nature of the invention. His creative "spark" was motivated by observation of a powerful spark and noting, "seemed so strong that it struck us forcibly there might be something more than induction." Edward H. Loftin claims the credit goes to himself Lt.-Commander Edward H. Loftin, U.S. Navy

Inventors of Radio - Thomas A. Edison

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Thomas A. Edison as he looked in 1883.
National Park Service Thomas A. Edison

Radio in 1885 - eleven years ahead of Marconi

By Eric Leslie

Edison's exact role in the history of wireless is clouded in confusion - of facts, of interpretations and even of language. One thing is clear. A dozen years before Hertz demonstrated the existence of radio waves, Edison had recognized a strange new phenomenon, which he named "etheric force" and predicted that it might be useful for communication.

Edison's discovery was due to his remarkable powers of observation. While working with a "vibrator magnet" one night in November, 1875, he noted a peculiar spark when a piece of metal was touched to the core of the magnet:

"It seemed so strong that it struck us forcibly there might be something more than induction. We now found that if we touched any metallic part of the vibrator or magnet we got this spark. The larger the body of iron touched to the vibrator the larger the spark. We now connected a wire to X. [Fig, 1] the end of the vibrating rod & we found we could get a spark by touching a piece of iron to it & one of the most curious phenomena is that if you turn the wire round on itself & let the wire touch any part of itself you get a spark .... This is simply wonderful & a good proof that the cause of the spark is a new unknown force."

Not everybody agreed, and when he demonstrated his new force at the Polyclinic Club of the American Institute, he created a small storm. His opponents seemed upset by the name "etheric force," which now seems either an extremely lucky accident or a marvelous burst of intuition. Others were more sympathetic, and The Operator, a telegraphers' journal, printed a long article, based on an interview with the young inventor, in which it was suggested that the force might be applicable to telegraphy:

"The cumbersome appliances of transmitting ordinary electricity, insulating knobs, cable sheathings, and so on, may be left out of the problem of quick and cheap telegraphic transmission; and a great saving of time and labor accomplished." An author in the Scientific American, Dec. 18, 1875, reports " ... by this simple means signals have been sent for long distances as from Mr. Edison's laboratory to his dwelling house in another part of the city, the only connection being the common system of gas pipes. Edison states that signals have also been sent the distance of 75 miles on an open circuit, by attaching a conducting wire to the Western Union telegraph line."

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Fig. 1 - Edison's vibrator.

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Fig. 2 - Edison's patent drawing shows the works of his "Means for Transmitting Signals Electrically."

Ten years later - May 23, 1885, still years before Hertz - Edison applied for a patent on a "Means for Transmitting Signals Electrically." The equipment (Fig. 2) consisted of an induction coil with a rotating or vibrating circuit breaker in the primary, and a high-voltage secondary with one end attached to a "condensing plate" on a high tower and the other to earth. The diagram looks like an operative radio hookup, though the type of inductance probably used and the breaking of the primary rather than the secondary circuit makes it probable that any radio frequency radiated came from the primary by capacitance, or was due to accidental sparking and arcing in the secondary. At any rate, the patent was considered good enough to be purchased for $30,000 by Marconi shortly before it expired.

Because of a confusion of language, Edison's wireless had been considered an induction device. Today "induction" is almost invariably an abbreviation of "electromagnetic induction." In 1885, with alternating current unheard of, it meant "electrostatic induction" unless qualified. The term is used in full by Edison in his patent.

The confusion is increased because the only practical application of the invention, the Lehigh Valley moving-

train "grasshopper telegraph" probably depended mainly on electromagnetic induction. Yet in describing that installation to a reporter, Edison said, "This invention uses what is called static electricity."

Edison's work on the vacuum tube, and his patented "Edison effect" on which all hot-cathode electron tubes are based, are too well known to mention here. With his etheric force, his wireless transmission patent, and the Edison effect, he had in his grasp a complete radio system. But he missed the opportunity to establish the first wireless communications network because he did not realize what these three things might do in combination. He himself was heard to remark much later in life that it was a pity he had not seen any connection between them.



Posted March 21, 2023

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