WHERE DID IT ALL START? A CHRONOLOGICAL HISTORY OF THE DEVELOPMENT OF RADIO 
- Up To The Start Of The Broadcasting Era -
 

by Greg Whiter, VK
4IG (Ex VK3CA)

 

Page 4 of 7 - Edourad Branly To Lee De Forest

Edourad Branly1892  EDOURAD BRANLY, French. Inventor of the coherer, which was later destined to play so large a part in the practical reception of wireless waves by Marconi. The coherer was not named as such until later, nor was it basically conceived by Branly, since Hughes had employed a similar device as mentioned earlier. Branly, however, made the device as Marconi was to use it, consisting of a tube containing loose zinc and silver filings and plugs to make contact at each end. Since the filings would cohere (stick together) after the first spark was received, a method of separating them for the next signal was necessary. Popoff (Russian) conceived the idea of using the vibrator and hammer from an (for those days) electric bell in the circuit so that, almost the instant the filings cohered, the hammer would strike the tube and cause them to “decohere”.

 

Nikola Tessla1893   NIKOLA TESLA, Siberian. Suggested a means of wireless communication, which used the earth as a conductor and created stationary electric waves on it. Invented the Tesla Coil, which, in effect, created high frequency oscillations of a broad nature (in reality was a broadband transmitter) but, since he made no effort to detect them, missed an opportunity of putting it “all together” and being the first; that was to be left up to Marconi. By 1905 Tesla had devised a means of wireless communication from his earlier experiments, but the Marconi system was well established at that time.

 

1895 - 1900   GUGLIELMO MARCONI, Italian. Considering the inventions and research of previous years, it is with no great surprise we find that scientists of this era looked upon Marconi as a non-scientific interloper full of audacity. In 1895 Marconi conducted experiments with “Hertzian waves”, and was able to send and receive messages over a distance of 1.25 miles (2 kilometres). He employed the coherer invented by Branly with Popoff’s tapper for decohering after signal was received. In fact his apparatus differed only very slightly from that of his predecessors when he applied for and was granted his first patent in England in 1896 for wireless telegraphy. From then on Guglielmo Marconihowever Marconi made rapid strides in the advancement of the art, being successful in transmitting and receiving messages between two warships over a distance of twelve miles (19 kilometres). In this year Marconi was successful in enlisting the backing of a number of wealthy Englishmen, and formed the Wireless Telegraph and Signal Company; he was made a director of this company and placed in charge of all development work although he was but then 23 years old. In 1899, he adapted to wireless Sir Oliver Lodge’s principles of syntony, (tuning or resonating - narrow-banding of circuits), perfecting it and obtaining a patent in 1900. It was a remarkable step forward in wireless transmission and reception, since it eliminated much of the interference caused by stations transmitting simultaneously, a problem of no mean proportions up to that time. In 1899, Marconi, was successful in covering distances up to 74 miles (125 kilometres) with his instruments, and ship to shore stations began to install his equipment. His activities and progress with wireless filtered through to America, and in 1899 he was invited there by the New York Herald which engaged him to report the New York yacht race held in October of that year. Marconi accepted for another reason, he wanted to interest the Unites States Navy in his equipment in the hope that it would make large purchases and thus help commercially exploit wireless. To facilitate matters, representatives of the British company financed and incorporated the Wireless Telegraph Company of America, to take care of the Marconi interests in that country. Marconi then went ahead with the transmission and reception of the yacht race results, and an amazedCoherer and Decoherer Receiver - 1900 American public obtained the news as to who had won, long before the ships had returned to port. From this angle Marconi’s efforts were thoroughly successful, but not so with the Navy. In demonstrations, the official witnesses were considerably impressed by the efficiency of his equipment, although in their reports mention was made of the interference obtained when two transmitters were operating simultaneously. Marconi, with success of his experiments on Lodge’s syntony or tuning still fresh in his mind, specified that this defect could be overcome. The deciding factor, however, against Marconi’s equipment were the terms of his proposed contract which the Navy definitely rejected. Thus for a while no further real progress was made in wireless in the USA. Marconi, in the meantime had gone back to England to continue with his experiments and make further rapid advancements in the art of wireless communication. His famous Atlantic transmission of the letter “S” (three dots) followed on December 12, 1901. PDF Article "Greatest Of All Amateurs - Marconi" by Hiram P Maxim, President of the ARRL, describing his meeting with Marconi - from the September 1922 issue of QST magazine.

 

Reginald A. Fessenden1900 - 1905   REGINALD A. FESSENDEN and LEE DE FOREST, Americans. If America is to boast outstanding contributors to the art or wireless in the early days, it is these two gentlemen who take accreditation.

Fessenden, while fully acquainted with Marconi’s wireless equipment – having experimented with these devices was more interested in radiotelephony. He knew that Marconi’s system was only adapted for damped-wave transmission and would not tolerate superimposing on it voice or further irregular waves. Consequently he began to experiment with continuous wave transmission (CW, today, a term which has come mean Morse code transmission) which led him to perfecting the arc transmitter. However the coherer would not receive the voice impulses modulated on an oscillating wave produced by the arc; so drawing on his electricity and chemical training Fessenden created the electrolytic detector, which allowed current to flow in only one direction. It consisted of a small aluminium cup filled with a solution of acid and water, into which a fine silver wire dipped. It was a tremendous improvement over the coherer and increased a receiver’s efficiency considerably. Later on Fessenden conceived the idea of employing an alternator as a continuous wave radio frequency source. While at the time he was laughed at, his idea was later to play a very important role in the progress of radio.

Meanwhile, de Forest was experimenting with wireless too, and in 1901 built a system less cumbersome and more efficient than Marconi’s. He to employed the electrolytic detector, which caused between himself and Fessenden considerable legal conflict that was later determined in Fessenden’s favour. De Forest secured some financial backing and formed the American Wireless Telegraph Company. With this company he commenced manufacturing equipment, some of which he sold to the Army. Unfortunately the company depended on stock promotion to finance its development work. It was soon in financial difficulties, which hampered it from getting into the commercial communications field. In this same period, 1904 to be exact, J Ambrose FlemingJ AMBROSE FLEMING, English, developed the two-element (diode) “valve” (so called  because of its characteristic of only allowing current flow in one direction) while employed by Marconi. He remembered Edison’s experiments and the so called “Edison effect” – since he had been a scientific adviser to the Edison Electric Light Company of America – and hence it occurred to him that the phenomenon could be employed to advantage as a detector of radio waves. This invention, which Fleming called the “glow lamp oscillation detector or oscillation valve”, was to enjoy only a short life inasmuch as De Forest’s discovery of the 3 element (triode) or audion tube was soon to follow.

 

Lee De Forest1906   DE FOREST’S Audion. Here is one of the greatest contributions of all to the early art of radio! It consisted only of the insertion of a grid between the filament and plate of Fleming’s “valve”, yet this addition of a third element so revolutionised radio that it continued in common use for another 70 years. While the power or the ability of the audion tube as an amplifier or oscillator had not yet been recognised, its merit as a detector was soonDe Forest's Audion Valve proven. Despite this invention and other meritorious work in the wireless field, De Forest’s finances were in extremely poor shape. To obtain the necessary capital he was forced to sell stock in his company, but somehow an unwilling public could not be persuaded to purchase. Later on, in 1912, to obtain funds for himself and his company, De Forest sold the rights to the Audion amplifier to the American Telephone and Telegraph Company for a paltry sum compared to its actual worth.

 

1907   First Crystal Detector,  by G. W. PICKARD. Up to this time the most popularCatwisker Detector detector was Fessenden’s electrolytic type; the coherer, while still somewhat used, having been found unstable and insensitive. The Fleming diode valve was never really popularised because of its insensitivity to weak signals. Consequently the discovery of the crystal detector marks another great stride in the Crystal Detectordevelopment of radio. Carborundum was first used by H. C. Dunwoody, of the U.S. Army in 1906, however it was Pickard who first used silicon to great effectiveness. He later determined that other minerals could be used, such as galena (lead ore) and iron pyrites. The crystal detector was extremely effective in demodulating feeble irregular signals (both modulated CW and damped waves) although somewhat critical in the adjustment of the “catwhisker”. Because of its sensitivity and inexpensiveness it was the most popular of all detectors until the advent of low cost audions, and was to a great extent responsible for increased public interest in wireless or radio.


Next Page - SS Republic, Titanic to the ARRL

Other Web Articles by the same author   EARLY YAESU MUSEN EQUIPMENT IN AUSTRALIA 
ORIGINS OF THE HANDIE TALKIE
THE HISTORY OF CLARK MASTS
THE EARLY HISTORY OF GFS ELECTRONICS

History Of Radio HOME PAGE


Links to other pages in this article
Page 1  In The Beginning - Static Electricity - 600 BC
Page 2  The Leyden Jar to Magnetism
Page 3  Samuel Morse To Heinrich Hertz
Page 4  Edourad Branly To Lee De Forest
Page 5  SS Republic to ARRL - PDF Article "Greatest Of All Amateurs - Marconi" by Hiram P Maxim - ARRL from Sept. 1922 QST article
Page 6  Alexanderson, RCA and Paul Godley - PDF Article "Story Of Godley's Achievements" from Feb 1922 1922 QST article
Page 7  Australian Radio Pioneer - Ernest Fisk


 

Any comments on this article should be directed to the author, Greg Whiter at: GregWhiter@portablemasts.com.au

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