History :: Early Radio
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"A bronze portrait bust in memory of the Italian who invented the wireless telegraphy, forerunner of the modern radio, is on a double pedestal. The granite base was a gift by the Marconi Memorial Foundation at a cost of $32,555 under an Act of Congress approved April 13, 1938. Completed June 30, 1941." Photo by Elizabeth Thomsen Flickr (cc)
Derived From: Captain Linwood S. Howeth, USN (Retired), History of Communications-Electronics in the United States Navy, Bureau of Ships and Office of Naval History (1963) (Govt Work: public domain)
1820: Hans Christian Oersted concludes that a wire with a current running through it generates an electric field. [Rescue at Sea]
"Light, heat and electromagnetic waves all travel with the same velocity but differ in wave length. The sun sets up both light and heat waves in the ether which travel earthward and become perceptible to the senses through the eyes, as light, and through the skin, as heat. Electromagnetic waves are not perceptible to any of the human senses, therefore, their use for the telegraphic transmission of intelligence requires manmade apparatus. In simplest form, this consists of: (1) equipment for generating and radiating these waves into the ether; and, (2) a conductor upon which these waves impinge, connected to a suitable receiving circuit. When the transmitted waves reach the conductor and travel down its length they set up a flow of alternating current within it. The voltage induced is directly proportional to the amplitude of the impinging wave at that point. When this conductor is connected to a receiving circuit capable of translating these voltage changes into aural or visual presentations the receiving equipment is complete." [Howeth]
"The beginning, but not the application, of the science of radio must be attributed to the scientific efforts and vision of Michael Faraday and the mathematical genius of James Clerk Maxwell. In devising a primitive dynamo, Faraday demonstrated that an energized conductor transmits lines of force into surrounding space and that these can be harnessed and translated into useable energy. He further envisioned that these lines of force extended to infinity and that they were, in some manner, related to light. Maxwell translated Faraday's ideas and visions into mathematical equations. He proved that electromagnetic waves travel through space, with a speed exactly equal to that of light, in a direction transverse to that in which they are propagated." [Howeth] See also [Rescue at Sea]
"Henrich Hertz was experimentally investigating the nature of electromagnetic waves. In conducting his experiments he developed an oscillator for generating high-frequency electromagnetic waves. Essentially, this oscillator was the first radio transmitter.
"A usable radio telegraph system still required a receiver capable of both detection and translation. Hertz developed a detector by adding metal balls to the ends of a wire about 7 feet long and then bending it into a ring with a short gap between the two balls. By increasing the area of the balls through the addition of small plates soldered to them, he was able to bring the ring into resonance with the oscillator. With the equipment in this "electrical condition" he was able to detect his oscillator transmissions, at distances up to 25 feet, by observing the spark across the gap of the detector.
"By further experimentation, Hertz was able to verify Maxwell's mathematical deductions. Additionally, he proved that electromagnetic waves obeyed the laws previously evolved concerning the action of light waves, and that they could be focused in beams of various widths by reflection from appropriately shaped metal surfaces." [Howeth]
In 1885 German physicist Heinrich Hertz though his proof of Maxwell's theories;
- that electromagnetic waves behave in the same way as light, and
- that light itself is electromagnetic in nature;
had no practical value since he could only send signals a few yards. Further, he saw no way of improving or amplifying the signal so that it could be received at a greater distance. Finally, his experiments showed that if two transmitters operated in the same proximity, the nearby receiver found both signals, producing nothing but static and hiss.
1887: Hertz detected radio waves and created radio waves with a Spark Gap Transmitter. [IEEE]
Radio Pioneers & Core Technologies, FCC History:
"For the first two decades of radio (1885-1906), spark gap machines served as the transmitters for most wireless telegraphy. A spark gap transmitter worked in combination with an induction coil, a Morse key, some power source - usually a battery, an earth ground, and an aerial. Power was applied to the coil with the Morse key acting as the on/off device for the power. Once power was received, a capacitor was charged, which caused a spark to jump across the gap between the two metal balls of the spark gap transmitter. This, in turn, caused a current to flow in a tuned circuit, which produced oscillations. By adding an aerial and earth ground, these oscillations could be sent through the atmosphere. Tuning the frequency of the oscillations was dependent on the type and properties of the capacitor and coil.
After selling his patents to Westinghouse in 1885, Tesla set up his own lab and worked on a wide variety of projects. These ranged from a carbon button lamp to experiments on the power of electrical resonance.
This last set of experiments, on what Tesla called "a simpler device" for the production of electric oscillations, resulted, in 1891, in the device known today as the Tesla Coil. A Tesla Coil is a transformer made up of two parts - a primary and secondary coil, one inside the other. When electrically charged the interaction between the two coils produces a voltage high enough to make the air conduct electric currents. Getting the power high enough to make the air an effective conductor of currents is key to wireless transmission of radio waves.
Tesla pursued the application of his coil technology to radio. By tuning a coil to a specific frequency he showed that the radio signal could be greatly magnified through resonant action. However, before he was able to fully demonstrate sending a radio signal 50 miles, his laboratory and equipment were destroyed in a fire.
1893: Nikola Tesla transmits radio waves. [IEEE]
One of the factors that helped the alternating current approach was Westinghouse's winning the contract to provide electrical light at the World's Columbian Exposition at Chicago in 1893. This Expo is identified by many scholars as one of the key events in America's burgeoning sense of itself as a major industrial power, leading the way in new technologies. The successful lighting of the Expo was then a factor in Westinghouse winning the contract to install the first hydroelectric power machinery at Niagara Falls. All of the enormous motors at the power station bore Tesla's name and patent numbers.
"Following disclosure of the knowledge gained by the efforts of Hertz, numerous individuals, in this country and abroad, intensified their efforts to develop a system of telegraphic communications without wires. In 1892, Sir William Preece signaled between two points on the Bristol Channel, Loch Ness, Scotland, employing both induction and conduction to affect one circuit by the current flowing in another. In the same year, another Englishman, C. A. Stevenson, suggested, without experimentation, that telegraphic communications could be established between ships by coils of wire, "the larger the diameter the better to get induction at a great distance." In a lecture before The Franklin Institute, in February 1893, Nikola Tesla described a plan for the transmission of power without wires. [Howeth]
"Prof. Edouard Branly, of France, developed his famous coherer in 1892. This device consists of a cell containing a granular conductor between two electrodes. When subjected to an electric current the granules cohere and become highly conductive. Unless the cell is jarred these granules continue to adhere to each other. When utilized in a radio receiving circuit the cell responds to the voltage rise, set up by the impinging radio waves, but afterwards continues to be a good conductor, unless, while the transmitting circuit is opened, it is jarred enough to decohere the granules. [Howeth]
"The addition of a trembler, activated by local battery, was a simple solution which required no intricate timing system, since it made little difference if the cell was continuously tapped.
"Sir Oliver Lodge is credited as being the first to conceive the idea of using this device for receiving radio signals. His receiver was made up of a spark gap (antenna) across the terminals of the coherer which in turn was also connected in series in a circuit containing a battery and a relay for closing a separate battery-powered local circuit containing the battery, an ink recorder, and the trembler in series. In 1894, he demonstrated this equipment before the British Association for the Advancement of Science. Despite the fact that all the necessary components were at hand, Lodge, occupied with his teaching at the University of Liverpool, neglected to commercialize his system immediately. [Howeth]
"The following year, Prof. A. S. Popoff improved Lodge's receiver by the insertion of choke coils on each side of the relay to protect the coherer and by replacing the spark gap with a vertical antenna insulated at its upper end and connected to the ground through the coherer. Popoff utilized his equipment to obtain information for a study of atmospheric electricity. Like Lodge, he was too engrossed with teaching and science to concern himself over its practical aspects. On 7 May 1895, in a lecture before the Russian Physicist Society of St. Petersburg, he stated he had transmitted and received signals at an intervening distance of 6 hundred yards. [Howeth]
"In the same year, Guglielmo Marconi, son of an Italian nobleman and an Irish mother, by using a Hertz oscillator and an antenna and a receiver very similar to Popoff's, successfully transmitted and received signals within the limits of his father's estate at Bologna, Italy. [Howeth] See also [Rescue at Sea]
"Marconi can scarcely be called an inventor. His contribution was more in the fields of applied research and engineering development. He possessed a very practical business acumen and he was not hampered by the same driving urge to do fundamental research which had caused Lodge and Popoff to procrastinate in the development of a commercial system. [Howeth]
In this era, telegraph was king, and the king of telegraph was Western Union. But telegraph depended upon wires - and wires dont reach boats too well - and wires dont hop ponds too well. Marconi saw a business opportunity - the ability to offer a communications service that wired telegraphy could not offer, and an opportunity to directly compete with Western Union.
"Forseeing little success in commercializing a radio system in Italy, he immediately set out for England where he applied for a British patent on his system, issued, in 1896 as No. 12,039. [Bradford (Marconi moved to England in 1896 after Italian government showed little interest)] [Nobel] The British Admiralty, with its need to be able to communicate with its ships, was quite receptive to the the possibilities of Marconi's work. [PBS Marconi]
1897: Guglelimo Marconi awarded radio patent. [IEEE]
Guglielmo Marconi (1908)
Source: Library of Congress (pd)"Through the efforts of Sir William Preece, and with the asset of a British patent guaranteeing his future rights, he succeeded in obtaining the financial support of wealthy Englishmen. On 20 July 1897, the Wireless Telegraphy and Signal Co., Ltd., was incorporated in England with a capitalization of £100,000. This company paid Marconi £15,000 in cash and £60,000 in stock for his patent in all countries, except Italy and her dependencies, which rights Marconi reserved for himself. The original purpose of the company was to provide radio telegraphy for lightships and lighthouses around the coast of England. In 1900, its name was changed to Marconi Wireless Telegraph Co., Ltd.; its purpose, to establish a worldwide monopoly in radio telegraphy. [Howeth] [Bradford][Nobel]
"In the effort to popularize the concept of monopoly control of wireless telegraphy and to further encourage other British people to invest, wide publicity was given the progress made in increasing the range of the equipment. Paralleling this, much effort was expended in educating people to consider Marconi as "the father of wireless telegraphy." These actions prompted an English writer to publish an article advising that, outside of England and a few of its colonies, other important commercial systems of wireless telegraphy were in more general use. Nevertheless, the founders of the Marconi Wireless Telegraph considered that only the Marconi interests had legal rights in this field and that their patent invalidated the use of radio by others, regardless of the circuitry used. In future years, this claim would be challenged many times and become the subject of considerable litigation. This concept did much to slow the development of radio. " [Howeth]
1898: Telsa demonstrates a remote control boat. [IEEE]
"Radio has been a primary medium for the distribution of news for many years. The Wireless Telegraph and Signal Co. did not underestimate the possibilities promised by this field. The Dublin, Ireland, Daily Express, impressed with the Marconi claims, saw a possible opportunity to "scoop" their competitors. Its owners invited Marconi to radio reports of the Kingston Regatta of July 1898 from the steamer Flying Huntress, the first ship fitted with radio equipment for commercial purposes. Marconi stated that his reporting of the races was entirely satisfactory in every respect and that over 700 messages were sent and received during the regatta. Mr. M. V. Snyder, representative of the New York Herald, reported to Mr. James Gordon Bennett, its owner, the success of the Daily Express' use of radio bulletins. He was later instrumental in bringing Marconi to America for a like purpose. [Howeth]
1899: Marconi transmits results from the America's Cup in the waters off New York. [Rescue at Sea]
"Early in 1899 two dramatic incidents focused worldwide attention upon the value of radio for maritime safety. In January of that year, the East Goodwin Sands Lightship, battered by heavy seas and with part of its bulwarks carried away, sent a radio message which quickly brought assistance. Only a few months later, the same lightship had a very narrow escape from sinking when, in a dense fog at 4 o'clock in the morning, March 1899, it was rammed by the steamer R. F. Mathews outward bound from London. The East Goodwin Lightship was one of four light vessels marking the Goodwin Sands, and fortunately it happened to be the one with a radio installation. It immediately flashed "We have just been run into by the steamer R. F. Mathews , of London. Steamship is standing by us. Our bows badly damaged." Received by the South Foreland Lighthouse, the message was relayed to Trinity House authorities at Ramsgate. Tugs were dispatched, the lightship was towed out of danger and the entire crew saved. It was later proven in Admiralty Court that property to the value of £52,588, had been salvaged by the action resulting from the one short radio report of the accident. [Howeth]
For wireless telegraphs had begun to appear on ocean-going vessels as early as 1891 - many of them donated for demonstration purposes by Marconi. For it was the opportunity to save lives and property on large ships that provided much of the early impetus to develop wireless communications via the radio waves. The 1899 collision between the coal-laden R. F. Matthews and the East Goodwin Lightship was just the first instance where the use of wireless radio saved lives. Because of the extremely dense fog and strong tides present that day, the lifeboats that came to the rescue might not have seen flares in time to get to the crash site prior to some loss of life. Thankfully the Trinity House Corporation, owner of the East Goodwin, was participating in a demonstration of Marconi radio systems and the ship's captain was able to quickly signal for help. [FCC]
Radio Pioneers & Core Technologies, FCC History Alexanderson came to the United States in 1902, at the age of 24, to work with General Electric on the new and exciting alternating current approaches to power generation. One of his early assignments was to build a transmitter that Reginald Fessenden could use to produce enough power to generate a continuous wave carrier. Fessenden's plan was to attach the sound waves from a human voice to this carrier wave and transmit this mix to radio receiving sets. To do this Fessenden knew that he needed a much higher frequency than the 60 Hertz produced by alternating generators of the time. To get a higher frequency he needed more power.
Through his own developments Fessenden had not been able to create a power generator that would produce even 1,000 Hertz. Nevertheless, in 1904, Fessenden contracted with General Electric for a machine which would generate a frequency of 100,000 Hertz.
The work took two years. In 1906 the Alexanderson Alternator, a 2 kilowatt, 100 kilohertz alternator, was used by Fessenden to carry out the first long distance broadcast of the human voice. Radio operators hundreds of miles in the Atlantic Ocean were astonished to hear a Bible and poetry reading. They were also treated to a woman singing opera, and a violin playing a Christmas carol.
Always knowing a good thing when he saw it, Marconi purchased 50 and 200 kilowatt Alexanderson Alternators for his trans-Atlantic transmissions. Marconi's Alexanderson Alternators, located in New Jersey, were used in 1918 to broadcast President Wilson's ultimatum to Germany at the close of WWI.
Unassuming Ernst Alexanderson produced over 300 patents and served as a leading figure in the development of facsimile communication and television as well as radio. Development of his alternators continued through the mid-1920's when 500,000 watt transmitters were developed. As great as these longwave alternators were they gave way in the late 1920's to vacuum tube shortwave transmitters that operated at a fraction of the cost and power.
Armstrong was 11 years old when Marconi's trans-Atlantic transmission occurred. It fired his imagination and he became a collector and creator of homemade wireless equipment. As a teenager his patient parents allowed him to build a 125 foot antenna in the yard so he could further his studies on radio. He was 16 when DeForest announced his Audion tube and one of these fragile, expensive tubes was added to his study equipment.
In 1912, as a junior at Columbia University he continued his interest in radio and the Audion tube by inventing a regenerative circuit that fed part of the current back to the grid in the tube. This strengthened the incoming signal. In fact, Armstong received distant stations so loudly that he could hear them without headphones - something unheard of at that time.
Further experiments led him to discover that by increasing the feedback into the tube even more he could produce rapid enough oscillations for the tube to act as a transmitter as well as a receiver. From this work Armstrong's regenerative circuit became the basis for continuous wave transmitters that are still at the heart of radio operations today.
When Armstrong entered the Army Signal Corp in WWI he did not leave the development of radio behind. Instead, as in so many areas of technology, work done for the U. S. military during times of war led to significant breakthroughs for civilian industry once the war was completed. So it was with vacuum tubes and radios during and after WWI.
In 1935 Armstrong revealed his final great work, motivated by his own dislike of the static he constantly heard on the radio. His original paper on frequency modulation was entitled "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation." Likely he did not imagine that this advance would be resisted. But, afraid that FM would make AM radio obsolete and slow down new developments in television, Armstrong's major financial backer withdrew its financial support. [IEEE]
So Armstrong established his own distribution channel by building a demonstration inter-city FM relay for New England 's Yankee Network. A shift in the location of the FM radio frequency, to accommodate the spectrum needs of the new television industry, made all Armstrong's FM equipment obsolete. It was not until the 1960's, after Armstrong's death, that the quality advantage of FM combined with stereo was enjoyed by most Americans.
Italian inventor Guglielmo Marconi's December 12, 1901 transmission of a wireless signal from Ireland to St. Johns, Newfoundland, Canada was an expression of faith as well as applied science. Marconi later described the prevailing skepticism of learned individuals by noting that achieving long distance wireless transmission of sound: [FCC] [Rescue at Sea] [Bradford (first towers built in Poldhu England and Cape Code were blown down by storms in the Fall of 1901)]"...had been declared to be impossible by some of the principal mathematicians of the time - (the) chief question mark (being) whether wireless waves would be stopped by the curvature of the earth...some eminent men held that the roundness of the earth would prevent communication over such great distances as the atlantic."
But the "pip-pip-pip" (Morse code for the letter "s") that Marconi reported he heard at 12:30 p.m. on December 12, 1901 was just one of many remarkable events that gave true meaning to Oliver Lodge's proclamation that wireless communications had created a new " epoch in history." [FCC][Bradford]
Thus, Marconi's integration of the work of Hertz, Righi, Branly, Lodge, and others led to an improved radio system based upon:
Anticipating a legal challenge from the Anglo-American Telegraph Company, Marconi moved from Newfoundland to Cape Breton in December 1901. Marconi had three radio stations in Cape Breton:
- Glace Bay
- South of Glace Bay
Dec. 15, 1902, Marconi successfully transmitted to Poldhu from his new Cape Breton station. After experimenting, Marconi settled on transmitting on 37.5 KHz and 54.5 KHz. A good history of the Canadian Towers is recounted by Bradford. The Cape Breton stations closed in 1926.
Canadian Reginald Fessenden was the larger than life man whose work, in combination with those others, introduced, in 1906, what we think of today as radio: music, news, talk, in fact any sound human beings can make. Experiences as the chief chemist in Edison's labs, work at Westinghouse, professorships in electrical engineering at Purdue University and the University of Pennsylvania, research in North Carolina for the U.S. Weather Bureau, and, finally, a founding partnership in the National Electric Signaling Company uniquely qualified him to solve the riddle of how sound waves traveled and what was necessary to transmit those waves wirelessly from one point to another. [FCC] [Rescue at Sea]
Although best known for his 1906 Christmas Eve broadcast of music and voice from Brant Rock, Massachusetts , Fessenden actually made the first transmission of voice in 1900 while under contract to the Weather Bureau. His continuous wave theory - whereby a sound wave is combined with a radio wave and transmitted to a receiver where the radio wave is removed so that the listener hears only the original sound - describes how radio works today. [IEEE] [FCC]
Fessenden proved his theory on December 23, 1900 from an island in the Potomac River. Speaking to an associate who was a mile away with a receiving unit, Fessenden said:"One - two - three - four, is it snowing where you are Mr. Thiessen? If it is, would you telegraph back to me?"
Thiessen replied in the affirmative and the rest, as they say, is history.
1901: Lee de Forest establishes American de Forest Wireless Telegraph. [deForest]
Lee DeForest, an Iowa preacher's son who earned a Yale PhD, announced his Audion vacuum tube in a Scientific American article in 1906. Although he acknowledged in this article that he didn't have a "completely satisfactory theory" as to why the tube amplified the reception of radio signals, understanding this curious tube led other researchers, such as Edwin Armstrong, to significant breakthroughs in amplifying both radio transmissions and reception before, during, and after WWI. [Rescue at Sea]
"The years 1902 and 1903 saw interest in radio increasing rapidly with the number of stations mushrooming, with their operations completely free and unrestricted. Commercial rivalry in the field was increasing in this country, much as it had in Europe a few years before. Unregulated competition, and the interference incident thereto, began to present a problem. Although some form of regulation had been advocated ever since the turn of the century, in this Nation, dedicated to the philosophy of free enterprise, it was slow in materializing.
"The Marconi interests were making rapid progress in establishing their radio monopoly by constructing shore stations in all the principal maritime countries. These stations were prohibited from handling messages from ships which did not lease Marconi equipment, thus making it undesirable for shipowners to equip their vessels with equipment of other manufacturers since such equipment would have limited use. The Marconi companies cannot be adjudged guilty of stock peddling. Although most of them operated under deficits for almost a decade, they made no fanciful promises to investors.
"In the United States the American De Forest Co. was the only serious competitor of the Marconi interests. Their ship installations were leased at far more reasonable costs but their business was almost totally limited to vessels engaged in the coastwise trade. [Howeth Chap VII]