Wireless telegraphy
Encyclopedia
Wireless telegraphy is a historical term used today to apply to early radio telegraph communications techniques and practices, particularly those used during the first three decades of radio (1887 to 1920) before the term radio came into use.
Wireless telegraphy originated as a term to describe electrical signaling without the electric wires to connect the end points. The intent was to distinguish it from the conventional electric telegraph signaling of the day that required wire connection between the end points. The term was initially applied to a variety of competing technologies to communicate messages encoded as symbols, without wires, around the turn of the 20th century, but radio emerged as the most significant.
Wireless telegraphy rapidly came to mean Morse code
transmitted with Hertzian waves (electromagnetic waves) decades before it came to be associated with the term radio
. It declined in popularity after the invention of radiotelephony, the ability to send sound by radio using amplitude modulation
, was introduced around 1920, sparking the beginning of broadcasting
. Radiotelegraphy continued to be used for point-to-point business, governmental, and military communication, and evolved into radioteletype
networks. Wireless telegraphy is still used widely today by amateur radio
, ham hobbyists where it is commonly referred to as radiotelegraphy, continuous wave
, or just CW.
and flag semaphore
. Maritime flags
and signal lamp
s are still in some use. A number of wireless electrical signaling schemes were investigated for telegraphy before practical radio systems became available. Wireless included such schemes as large mechanical arms for visual signalling and electrical currents through water and dirt.
The first thoughts about wireless telegraph transmissions date back to the earliest days of the electric telegraph. The original telegraph used two wires to connect the two legs or "poles" of the electrical apparatus of two stations to form a complete electrical circuit
or "loop". In 1837 however, Carl August von Steinheil
of Munich
, Germany
found that by connecting one leg of the apparatus at each station to metal plates buried in the ground, he could eliminate one wire and use a single wire for telegraphic communication. This led to speculation that it might be possible to eliminate both wires, and transmit telegraph signals through the ground without any wires connecting the stations. Other attempts were made to send the electric current through bodies of water, in order to span rivers, for example. Prominent experimenters along these lines included Samuel F. B. Morse
in the United States and James Bowman Lindsay
in Great Britain.
Telegraphic communication using earth conductivity was eventually found to be limited to impractically short distances, as was communication conducted through water, or between trenches during World War I.
, in the mid-1880s, patented an electromagnetic induction system he called "grasshopper telegraphy", which allowed telegraphic signals to jump the short distance between a running train and telegraph wires running parallel to the tracks. This system was successful technically but not economically, as there turned out to be little interest by train travelers in an on-board telegraph service. . During the Great Blizzard of 1888
, this system was used to send and receive wireless messages from trains buried in snowdrifts, perhaps the first successful use of wireless telegraphy to send distress calls. The disabled trains were able to maintain communications via their Edison induction wireless telegraph systems.
The most successful creator of an electromagnetic induction telegraph system was William Preece in Great Britain. Beginning with tests across the Bristol Channel in 1892, Preece was able to telegraph across gaps of about five kilometers. However, his induction system required extensive lengths of antenna wires, many kilometers long, at both the sending and receiving ends. The length of those sending and receiving wires needed to be about the same length as the width of the water (or land) that needed to be spanned. For example, for Preece's station to span the English Channel
from Dover, England, to the coast of France
would require sending and receiving wires of about 30 miles (50 kilometers) along the two coasts. These facts made it impractical to use Preece's system on either ship
s, boat
s, or ordinary island
s (ones much smaller than Great Britain
or Greenland
), and the relatively short distances that a practical Preece system could span meant that it had few advantages over underwater telegraph cables.
from Dundee to Woodhaven (now part of Newport-on-Tay), a distance of two miles (three kilometers).
in the early 19th century, when it was discovered that radio waves could be used to send telegraph messages. After James Clerk Maxwell
had predicted the existence of electromagnetic waves, and had shown that their speed of propagation is identical with that of light, it required, in reality, very little to demonstrate by experiment the existence of such waves.
at Fermo
in Italy developed a primitive device that responded to radio waves. It consisted of a tube filled with iron
filings, called a "coherer
". This kind of device would later be developed to become the first practical radio detector
. Writing in the Rendiconti of the Lombardy Institution regarding the discovery of the coherer, directs attention to his experiments made in 1884, before Branly had worked on the subject. He further points out the part played by Augusto Righi
in wireless telegraphy.
Edward Branly was preceded in the way he conducted his research by the Italian professor Temistocle Calzecchi-Onesti, who, 1884 and 1885 has the publiesed in Nuovo Cimento
results he obtained. The experience is typical Calzecchi interesting for the object at hand. Having placed a small quantity of filings copper between two pieces of brass, he found through a battery and a galvanometer that, depending on the degree of compaction, the powder was conductive or insulating and that the case presented some interesting features.
Circuit already including the filings tube and galvanometer Wiedemann, he added a phone and a mercury switch to eliminate at will the filings tube and the galvanometer and do replace them by a short circuit. This prepared, he noted, through the galvanometer, that the tube gave way to a very low current. He then introduced the short-circuit: a shock produced in the phone indicated the presence of current intense enough. Ending the short-circuit and restoring the tube and the galvanometer, he found that the tube had become a driver. It also showed that this effect was due to the extra current to begin opening in the coil of the phone. He verified the fact with various powders and found that some of them become conductive under the action of this simple spark of extra current, while others were changed by the more powerful action of static machines.
Experiments Calzecchi were not widely reported when they are published, not linked to any important issue to the agenda fell into oblivion. Mr. Hranly, which carefully outlined the work that touched on his own research when he published them, ignored them and it certainly took the controversy raised by the claims Marconi prissent the acute nature that they have acquired This memory was pulled from oblivion. He would later write, Le mie esperienze e di Edoardo quelle Branly Sulla conduttività elettrica delle limature metalliche.
studied Maxwell's theory and validated it through experiment. He demonstrated the transmission and reception of the electromagnetic waves predicted by Maxwell and intentionally transmitted and received radio. Hertz changed the frequency of his radiated waves by altering the inductance or capacity of his radiating conductor or antenna, and reflected and focused the electromagnetic waves, thus demonstrating the correctness of Maxwell's electromagnetic theory of light. Famously, he saw no practical use for his discovery.
In his UHF
experiments, he transmitted and received radio waves over short distances and showed that the properties of radio waves were consistent with Maxwell’s electromagnetic theory. He demonstrated that radio radiation had all the properties of waves (now called electromagnetic radiation), and discovered that the electromagnetic equations could be reformulated into a partial differential equation
called the wave equation
.
Heinrich Hertz (1888) demonstrated the existence of electromagnetic radiation (radio waves) in a series of experiments in Germany during the 1880s. Hertz showed methods of producing, detecting, and measuring these waves. It had been known for many years, from the predictions of Kelvin and Von Helmholtz, and confirmed by the experiments of Fedderssen, that in many cases an electric discharge is of an oscillatory character. In the years 1887-8, Lodge, Fitzgerald, and others were investigating the nature of these oscillations, and the manner in which they are guided by conducting wires, when Hertz conceived the idea of investigating the disturbances which such oscillatory discharges set up in the surrounding space.
Hertz used the damped oscillating currents in a dipole antenna, triggered by a high-voltage electrical capacitive spark
discharge, as his source of radio waves. His detector in some experiments was another dipole antenna connected to a narrow spark gap. A small spark in this gap
signified detection of the radio waves. When he added cylindrical reflectors behind his dipole antennas, Hertz could detect radio waves about 20 metres from the transmitter
in his laboratory
. He did not try to transmit further because he wanted to prove electromagnetic theory
, not to develop wireless communication
s.
In the collection of physical instruments at the Technical High School
at Karlsruhe
(where these researches were carried out), Hertz had found and used for lecture purposes a pair of so-called Eiess spirals or Knochenhauer spirals. Hertz had been surprised to find that it was not necessary to discharge large batteries through one of these spirals in order to obtain sparks in the other; that small Leyden jar
s amply sufficed for this purpose, and that even the discharge of a small induction coil
would do, provided it had to spring across a spark gap. In altering the conditions Hertz came upon the phenomenon of side-sparks, which formed the starting point of his research. At first Hertz thought the electrical disturbances would be too turbulent and irregular to be of any further use, but when he had discovered the existence of a neutral point in the middle of a side-conductor, and therefore of a clear and orderly phenomenon, he felt convinced that the problem of the Berlin Academy was now capable of solution. His ambition at the time did not go further than this. Hertz's conviction was naturally strengthened by finding that the oscillations with which he had to deal were regular.
Hertz’s setup for a source and detector of radio waves (then called Hertzian waves in his honor) was the first intentional and unequivocal transmission and reception of radio waves
through free space
. The first of the papers published ("On Very Rapid Electric Oscillations") gives, generally in the actual order of time, the course of the investigation as far as it was carried out up to the end of the year 1886 and the beginning of 1887.
Hertz, though, did not devise a system for actual general use nor describe the application of the technology and seemed uninterested in the practical importance of his experiments. He stated that "It's of no use whatsoever ... this is just an experiment that proves Maestro Maxwell was right — we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there."
Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess." Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application." Hertz died in 1894, so the art of radio was left to others to implement into a practical form.
demonstrated what he later called the "radio-conductor," which Lodge in 1893 named the coherer
, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, Dr. Branly discovered that loose metal filings, which in a normal state have a high electrical resistance, lose this resistance in the presence of electric oscillations and become practically conductors of electricity. This Branly showed by placing metal filings in a glass box or tube, and making them part of an ordinary electric circuit. According to the common explanation, when electric waves are set up in the neighborhood of this circuit, electromotive forces are generated in it which appear to bring the filings more closely together, that is, to cohere, and thus their electrical resistance decreases, from which cause this piece of apparatus was termed by Sir Oliver Lodge a coherer. Hence the receiving instrument, which may be a telegraph relay, that normally would not indicate any sign of current from the small battery, can be operated when electric oscillations are set up. Prof. Branly further found that when the filings had once cohered they retained their low resistance until shaken apart, for instance, by tapping on the tube.
In On the Changes in Resistance of Bodies under Different Electrical Conditions, he described how the electrical circuit was made by means of two narrow strips of copper parallel to the short sides of the rectangular plate, and forming good contact with it by means of screws. When the two copper strips were raised the plate was cut out of the circuit. He also used as conductors fine metallic filings, which he sometimes mixed with insulating liquids. The filings were placed in a tube of glass or ebonite
, and were held between two metal plates. When the electrical circuit, consisting of a Daniell cell
, a galvanometer
of high resistance, and the metallic conductor, consisting of the ebonite plate, and the sheet of copper, or of the tube containing the filings, was completed, only a very small current flowed; but there was a sudden diminution of the resistance which was proved by a large deviation of the galvanometer
needle when one or more electric discharges were produced in the neighbourhood of the circuit. In order to produce these discharges a small Wimshurst influence machine was used, with or without a condenser, or a Ruhmkorff coil. The action of the electrical discharge diminished as the distance increases; but he observed it easily, and without taking any special precautions, at a distance of several yards. By using a Wheatstone bridge
, he observed this action at a distance of 20 yards, although the machine producing the sparks was working in a room separated from the galvanometer and the bridge by three large apartments, and the noise of the sparks was not audible. The changes of resistance were considerable with the conductors described. They varied, for instance, from several millions of ohms to 2000, or even to 100, from 150,000 to 500 ohms, from 50 to 35, and so on. The diminution of resistance was not momentary, and sometimes it was found to remain for twenty-four hours. Another method of making the test was, by connecting the electrodes of a capillary electrometer to the two poles of a Daniell cell with a sulphate of cadmium solution. The displacement of mercury which took place when the cell was short-circuited, only took place very slowly when an ebonite plate, covered with a sheet of copper of high resistance, was inserted between one of the poles of the cell, and the corresponding electrode of the electrometer; but when sparks were produced by a machine, the mercury was rapidly thrown into the capillary tube owing to the sudden diminution in the resistance of the plate.
Branly found that, upon examination of the conditions necessary to produce the phenomena, the following data:
Summing up, he stated that in all these tests the use of ebonite plates covered with copper or mixtures of copper and tin was less satisfactory than the use of filings; with the plates he was unable to obtain the initial resistance of the body after the action of the spark or of the current, while with the tubes and filings the resistance could be brought back to its normal value by striking a few sharp blows on the support of the tube.
The disadvantages of the coherer are it is erratic nature in its sensitiveness, which may be much decreased by local discharges, such as the spark discharges of the transmitter
, and it responds to atmospheric disturbances or lightning discharges. Consequently, the coherer cannot be relied upon as a calling-up apparatus. With strong impulses of energy in the receiver it enables one to print the received message, but for long-distance work it is not as sensitive as some other detectors which are of more developed in the inter-war period before the roaring Twenties
.
and Pontifical Gregorian University
, where he studied physics and chemistry. He completed his clerical training in Rome, graduating in theology and was ordained priest in 1886. In Rome, he started studying physics and electricity. When he returned to Brazil, he conducted experiments in wireless in Campinas
and São Paulo
(1892–1893). In the "Porto Jornal da Manha", he is said to have conducted between 1890 and 1894 wireless transmissions in telegraphy and telephony over distances of up to 8 kilometres (5 mi).
, Missouri
, Nikola Tesla
made the first public demonstration of a modern wireless system in 1893. Addressing the Franklin Institute
in Philadelphia and the National Electric Light Association
, he described and demonstrated in detail the principles of wireless telegraphy and radio. The apparatus that he used contained all the elements that were incorporated into radio
systems before the development of the vacuum tube
. This led to work in using radio signals for wireless communication, initially with limited success. Using spark-gap transmitters plus coherer-receivers were tried by many experimenters, but several were unable to achieve transmission ranges of more than a few hundred metres. This was not the case for all researchers in the field of the wireless arts, though.
In 1891, Nikola Tesla
began his research into radio. Around July 1891, Tesla developed various alternator apparatus
that produced 15,000 cycles per second
. In 1892 he gave a lecture called "Experiments with Alternate Currents of High Potential and High Frequency". Tesla delivered the presentation before the Institution of Electrical Engineers
of London (February 3, 1892) in which he suggested that messages could be transmitted without wires. He repeated this to the Royal Institution
(February 4, 1892). He would again repeat the presentation to the Société Française de Physique (February 19, 1892) in Paris. Tesla realized he gained, by the use of very high frequencies, many advantages in his experiments, such as the possibility of working with one lead and the possibility of doing away with the leading-in wire. In transmitting impulses through conductors, he dealt with high pressure and high flow, in the ordinary interpretation of these terms. Towards the end of the lecture, he proposed that sending over the wire current vibrations of very high frequencies at enormous distance without affecting greatly the character of the vibrations and that telephony could be rendered practicable across the Atlantic. He also proposed that intelligence — transmitted without wires — transmission through the Earth and to establish the physical mechanism of such a circuit. Tesla captured the attention of the whole scientific world by his fascinating experiments on high frequency electric currents. He stimulated the scientific imagination of others as well as displayed his own, and created a widespread interest in his brilliant demonstrations. Accordingly there are seven elements in the complete oscillation-producing appliance, which are as follows:
These several elements have each to be considered separately with reference to their best practical forms for various purposes. When the key is closed, and the apparatus in operation, there are trains of intermittent electrical oscillations set up in the circuit, and if the terminals of the secondary circuit of the oscillation transformer are near together, there is high potential high frequency oscillatory sparks passing between them. The above-described apparatus in a typical form is generally called a Tesla apparatus for the production of high frequency electric currents.
In 1893, at St. Louis, Missouri
, Tesla gave a public demonstration, "On Light and Other High Frequency Phenomena", of wireless communication. Addressing the Franklin Institute
in Philadelphia, he described in detail the principles of early radio communication. The lecture apparatus that Tesla used contained all the elements that were incorporated into radio systems before the development of the "oscillation valve", the early vacuum tube
. The lecture delivered before the Franklin Institute, at Philadelphia, occurred on February 24, 1893. The variety of Tesla's radio frequency systems were again demonstrated during when he presented to meetings of the National Electric Light Association
, at St. Louis, on March I, 1893. Afterward, the principle of radio communication (sending signals through space to receivers) was publicized widely from Tesla's experiments and demonstrations. On August 25, 1893, Tesla delivered the lecture "Mechanical and Electrical Oscillators", before the International Electrical Congress, in the hall adjoining the Agricultural Building, at the World's Fair, Chicago
. This helped popularize radio communication activity worldwide, which is covered in depth by Invention of Radio
and History of Radio
.
The high-frequency phenomena which Tesla first developed and displayed had scientific rather than practical interest; but Tesla called attention to the fact that by taking the Tesla oscillator, grounding one side of it and connecting the other to an insulated body of large surface, it should be possible to transmit electric oscillations to a great distance, and to communicate intelligence in this way to other oscillators in sympathetic resonance therewith. This was going far toward the invention of radio-telegraphy as then known.
Transmission and radiation of radio frequency energy was a feature exhibited in the experiments by Tesla which he proposed might be used for the telecommunication
of information
. The Tesla method
was described in New York in 1897.
In 1894, T. C. Martin
publishes "The Inventions, Researches and Writings of Nikola Tesla", detailing the work of Tesla in the previous years. Various scientists, inventors, and experimenters began to investigate wireless methods. Telsa's work contained coupled oscillation circuits having capacity and inductance in series. In 1897, Tesla applied for two key United States radio patents, , first radio system patent, and . Tesla also used sensitive electromagnetic receivers, that were unlike the less responsive coherer
s later used by Marconi and other early experimenters. Shortly thereafter, he began to develop wireless remote control devices.
conducted a series of demonstrations with a radio system for signalling for communications over long distances
. Marconi is said to have read, while on vacation in 1894, about the experiments that Hertz did in the 1880s. Marconi also read about Tesla's work. It was at this time that Marconi began to understand that radio waves could be used for wireless communications. Marconi's early apparatus was a development of Hertz’s laboratory apparatus into a system designed for communications purposes. At first Marconi used a transmitter to ring a bell in a receiver in his attic laboratory. He then moved his experiments out-of-doors on the family estate near Bologna, Italy, to communicate farther. He replaced Hertz’s vertical dipole with a vertical wire topped by a metal sheet, with an opposing terminal connected to the ground. On the receiver side, Marconi replaced the spark gap with a metal powder coherer, a detector developed by Edouard Branly
and other experimenters. Marconi transmitted radio signals for about a mile at the end of 1895.
By 1896, Marconi introduced to the public a device in London
, asserting it was his invention. Despite Marconi's statements to the contrary, though, the apparatus resembles Tesla's descriptions in his research, demonstrations and patents. Marconi's later practical four-tuned system was pre-dated by N. Tesla, Oliver Lodge, and J. S. Stone. He filed a patent on his earliest system with the British Patent Office on June 2, 1896.
In 1897, Marconi was awarded a patent for radio with British patent No. 12,039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. The complete specification was filed March 2, 1897. This was Marconi's initial patent for the radio, though it used various earlier techniques of various other experimenters (primarily Tesla) and resembled the instrument demonstrated by others (including Popov). During this time spark-gap wireless telegraphy was widely researched. In July, 1896, Marconi got his invention and new method of telegraphy to the attention of Preece, then engineer-in-chief to the British Government Telegraph Service, who had for the previous twelve years interested himself in the development of wireless telegraphy by the inductive-conductive method. On June 4, 1897, he delievers "Signalling through Space without Wires". Preece devoted considerable time to exhibiting and explaining the Marconi apparatus at the Royal Institution
in London, stating that Marconi invented a new relay which had high sensitiveness and delicacy.
In 1896, Jagdish Chandra Bose
went to London on a lecture tour and met Marconi, who was conducting wireless experiments for the British post office. The Marconi Company Ltd. was founded by Marconi in 1897, known as the Wireless Telegraph Trading Signal Company. Also in 1897, Marconi established the radio station at Niton, Isle of Wight
, England. Marconi's wireless telegraphy was inspected by the Post Office Telegraph authorities; they made a series of experiments with Marconi's system of telegraphy without connecting wires, in the Bristol Channel
. The October wireless signals of 1897 were sent from Salisbury Plain
to Bath, a distance of thirty-four miles. Marconi's reputation is largely based on the making of his law
(1897), and other accomplishments in radio communications and commercializing a practical system.
Other experimental stations were established at Lavernock Point, near Penarth
; on the Flat Holmes, an island in mid-channel, and at Brean Down
, a promontory
on the Somerset
side. Signals were obtained between the first and last-named points, a distance of, approximately, eight miles. The receiving instrument used was a Morse inkwriter of the Post Office pattern.
s and primitive receivers made it practical to send telegraph messages over great distances, enabling transcontinental and ship-to-shore signalling. Before that time, wireless telegraphy was an obscure experimental term that applied collectively to an assortment of sometimes unrelated signalling schemes. In 1898, Tesla demonstrated a radio controlled boat in Madison Square Garden
that allowed secure communication
between transmitter and receiver.
In 1899, de Moura transmitted the human voice from the College of the Sisters of St. Joseph
, high in the district of Santana, Brazil, north of the capital city. Also made public demonstrations of his invention on June 3, 1900, being reported by the Jornal do Commercio (June 10, 1900), "Last Sunday, on top of Santana in São Paulo , Padre Landell de Moura has particular experience with various devices of his invention. In order to demonstrate some laws which he discovered in studying the propagation of sound, the light and electricity through space, which were crowned with brilliant success." The experiences were performed in the presence of the English Vice Consul S. Paul, Percy Parmenter, Charles Lupton
, and other persons of high social position. Upon observing the experiments, Rodriguez Botet, giving news of the trials, said he was not far from the moment of the consecration of Landell as an author of radio discoveries. The wireless telephony is reputed the most important discoveries of Landell. De Moura did later pursue and receive several patents on wireless technology. He would later obtain for a wireless telephone.
In 1898, Marconi opened a radio factory in Hall Street, Chelmsford, England, employing around 50 people. In 1899, Marconi announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London. In May, 1898, communication was established for the Corporation of Lloyds
between Ballycastle
and the Lighthouse
on Rathlin Island
in the North of Ireland. In July, 1898, the Marconi telegraphy was employed to report the results of yacht races at the Kingston Regatta
for the Dublin Express
newspaper. A set of instruments were fitted up in a room at Kingstown, and another on board a steamer, the Flying Huntress. The aerial conductor on shore was a strip of wire netting attached to a mast 40 feet high, and several hundred messages were sent and correctly received during the progress of the races.
At this time His Majesty King Edward VII, then Prince of Wales
, had the misfortune to injure his knee, and was confined on board the royal yacht Osltorm in Cowes Bay.
Marconi fitted up his apparatus on board the royal yacht by request, and also at Osborne House
, Isle of Wight, and kept up wireless communication for three weeks between these stations. The distances covered were small; but as the yacht moved about, on some occasions high hills were interposed, so that the aerial wires were overtopped by hundreds of feet, yet this was no obstacle to communication. These demonstrations led the Corporation of Trinity House to afford an opportunity for testing the system in practice between the South Foreland Lighthouse
, near Dover, and the East Goodwin Lightship, on the Goodwin Sands
. This installation was set in operation on December 24, 1898, and proved to be of value. It was shown that when once the apparatus was set up it could be worked by ordinary seamen with very little training.
At the end of 1898 electric wave telegraphy established by Marconi had demonstrated its utility, especially for communication between ship and ship and ship and shore. The Haven Hotel
station and Wireless Telegraph Mast was where much of Marconi's research work on wireless telegraphy was carried out after 1898. In 1899, W. H. Preece delivers "Aetheric Telegraphy", stating that the experimental stage in wireless telegraphy had been passed in 1894 and inventors were then entering the commercial stage. Preece, continuing in the lecture, details the work of Marconi and other British inventors. The Marconi Company was renamed Marconi's Wireless Telegraph Company in 1900. In 1899 he transmitted messages across the English Channel
. The British Navy experiments with Marconi's system in the Anglo-Boer War from 1899-1902 was the first use of operational wireless telegraphy in the field.
In 1901, Marconi claimed to have received daytime transatlantic radio frequency signals at a wavelength of 366 metres
(820 kHz). Marconi established a wireless transmitting station at Marconi House, Rosslare Strand, Co. Wexford in 1901 to act as a link between Poldhu in Cornwall and Clifden in Co. Galway. His announcement on 12 December 1901, using a 152.4 metres (500 ft) kite-supported antenna for reception, stated a the message was received at Signal Hill in St John's
, Newfoundland
(now part of Canada) via signals transmitted by the company's new high-power station at Poldhu
, Cornwall
. The message received was the Morse letter 'S' - three dots. Bradford has recently contested this, however, based on theoretical work as well as a reenactment of the experiment; it is possible that what was heard was only random atmospheric noise, which was mistaken for a signal, or that Marconi may have heard a shortwave
harmonic
of the signal. The distance between the two points was about 3500 kilometres (2,174.8 mi).
Marconi transmitted from England to Canada and the United States. In 1902, a Marconi station
was established in the village of Crookhaven
, County Cork
, Ireland
to provide marine radio communications to ships arriving from the Americas. A ship's master could contact shipping line agents ashore to enquire which port was to receive their cargo without the need to come ashore at what was the first port of landfall. Ireland was also, due to its western location, to play a key role in early efforts to send trans-Atlantic messages. Marconi transmitted from his station in Glace Bay, Nova Scotia, Canada across the Atlantic, and on 18 January 1903 a Marconi station sent a message of greetings from Theodore Roosevelt
, the President of the United States, to the King of the United Kingdom, marking the first transatlantic radio transmission originating in the United States.
, the "Radio Priest", conducted a great deal of revolutionary work in wireless telegraphy. He established a laboratory in Wilkes-Barre, in which he primarily investigated radiotelegraphy. His article in the Tovaryšstvo magazine of 1900 shows that his radiotelegraphy studies had achieved a high level. In 1904, he received his first two US patents: the Apparatus for wireless telegraphy and The way of transmitted messages by wireless telegraphy. Further 11 patents followed between 1907 and 1911. Based on the first two patents, he created the Universal ether Telegraph Co., which organized a public test of Murgaš's transmitting and receiving facilities in September 1905. The test was successful, but a storm destroyed the antenna masts three month later, which led to a dissolution of the company.
In 1906, Lee De Forest
brought out a vacuum tube device which he called the "audion
" and which has been described in the A.I.E.E. Transactions. This was a very sensitive detector of electric oscillations and consisted of three electrodes in an exhausted envelope. One of the electrodes could be heated to incandescence with the result that electrons were emitted by it (the Edison effect).
When the United States entered World War I
, private radiotelegraphy stations were prohibited, which put an end to several pioneer's work in this field. By the 1920s, there was a worldwide network of commercial and government radiotelegraphic stations, plus extensive use of radiotelegraphy by ships for both commercial purposes and passenger messages. The ultimate implementation of wireless telegraphy was telex
using radio signals, which was developed in the 1930s and was for many years the only reliable form of communication between many distant countries. The most advanced standard, CCITT
R.44, automated both routing and encoding of messages by short wave transmissions. (See telegraphy
for more information).
Other
Wireless telegraphy originated as a term to describe electrical signaling without the electric wires to connect the end points. The intent was to distinguish it from the conventional electric telegraph signaling of the day that required wire connection between the end points. The term was initially applied to a variety of competing technologies to communicate messages encoded as symbols, without wires, around the turn of the 20th century, but radio emerged as the most significant.
Wireless telegraphy rapidly came to mean Morse code
Morse code
Morse code is a method of transmitting textual information as a series of on-off tones, lights, or clicks that can be directly understood by a skilled listener or observer without special equipment...
transmitted with Hertzian waves (electromagnetic waves) decades before it came to be associated with the term radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
. It declined in popularity after the invention of radiotelephony, the ability to send sound by radio using amplitude modulation
Amplitude modulation
Amplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
, was introduced around 1920, sparking the beginning of broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
. Radiotelegraphy continued to be used for point-to-point business, governmental, and military communication, and evolved into radioteletype
Radioteletype
Radioteletype is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers running software to emulate teleprinters, connected by radio rather than a wired link.The term radioteletype is used to...
networks. Wireless telegraphy is still used widely today by amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
, ham hobbyists where it is commonly referred to as radiotelegraphy, continuous wave
Continuous wave
A continuous wave or continuous waveform is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration. Continuous wave is also the name given to an early method of radio transmission, in which a carrier wave is switched on and off...
, or just CW.
The Brief history of the development
Wireless', or Space Telegraphy's, detailed history and growth of the art includes the work of Tesla, Lodge, Marconi, Braun, Fessenden, Fleming, De Forest and many others. Radio telegraphy is described in books written with this professed purpose; in fact a book of considerable dimensions is required to do justice to the historical side of the subject.Ground and water conduction
The term "wireless" can be applied to numerous telegraphic signaling technologies other than radio. Historically, technologies have ranged from smoke signals and talking drums to the heliographHeliograph
A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter...
and flag semaphore
Flag semaphore
Semaphore Flags is the system for conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the flag is in a fixed position...
. Maritime flags
International maritime signal flags
The system of international maritime signal flags is one system of flag signals representing individual letters of the alphabet in signals to or from ships...
and signal lamp
Signal lamp
A signal lamp is a visual signaling device for optical communication . Modern signal lamps are a focused lamp which can produce a pulse of light...
s are still in some use. A number of wireless electrical signaling schemes were investigated for telegraphy before practical radio systems became available. Wireless included such schemes as large mechanical arms for visual signalling and electrical currents through water and dirt.
The first thoughts about wireless telegraph transmissions date back to the earliest days of the electric telegraph. The original telegraph used two wires to connect the two legs or "poles" of the electrical apparatus of two stations to form a complete electrical circuit
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
or "loop". In 1837 however, Carl August von Steinheil
Carl August von Steinheil
Carl August von Steinheil was a German physicist, inventor, engineer and astronomer.-Biography:Steinheil was born in Ribeauvillé, Alsace. He studied law in Erlangen since 1821, then astronomy in Göttingen and Königsberg. He continued his studies in astronomy and physics when he started living on...
of Munich
Munich
Munich The city's motto is "" . Before 2006, it was "Weltstadt mit Herz" . Its native name, , is derived from the Old High German Munichen, meaning "by the monks' place". The city's name derives from the monks of the Benedictine order who founded the city; hence the monk depicted on the city's coat...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
found that by connecting one leg of the apparatus at each station to metal plates buried in the ground, he could eliminate one wire and use a single wire for telegraphic communication. This led to speculation that it might be possible to eliminate both wires, and transmit telegraph signals through the ground without any wires connecting the stations. Other attempts were made to send the electric current through bodies of water, in order to span rivers, for example. Prominent experimenters along these lines included Samuel F. B. Morse
Samuel F. B. Morse
Samuel Finley Breese Morse was an American contributor to the invention of a single-wire telegraph system based on European telegraphs, co-inventor of the Morse code, and an accomplished painter.-Birth and education:...
in the United States and James Bowman Lindsay
James Bowman Lindsay
James Bowman Lindsay was a Scottish inventor and author. He is credited with early developments in several fields, such as incandescent lighting and telegraphy.- Life and work :...
in Great Britain.
Telegraphic communication using earth conductivity was eventually found to be limited to impractically short distances, as was communication conducted through water, or between trenches during World War I.
Electrostatics and electromagnetics
Both electrostatic and electromagnetic induction were used to develop wireless telegraph systems which saw limited commercial application. In the United States, Thomas EdisonThomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...
, in the mid-1880s, patented an electromagnetic induction system he called "grasshopper telegraphy", which allowed telegraphic signals to jump the short distance between a running train and telegraph wires running parallel to the tracks. This system was successful technically but not economically, as there turned out to be little interest by train travelers in an on-board telegraph service. . During the Great Blizzard of 1888
Great Blizzard of 1888
The Great Blizzard of 1888 or Great Blizzard of '88 was one of the most severe blizzards in United States' recorded history. Snowfalls of 40-50 inches fell in parts of New Jersey, New York, Massachusetts and Connecticut, and sustained winds of over produced snowdrifts in excess of...
, this system was used to send and receive wireless messages from trains buried in snowdrifts, perhaps the first successful use of wireless telegraphy to send distress calls. The disabled trains were able to maintain communications via their Edison induction wireless telegraph systems.
The most successful creator of an electromagnetic induction telegraph system was William Preece in Great Britain. Beginning with tests across the Bristol Channel in 1892, Preece was able to telegraph across gaps of about five kilometers. However, his induction system required extensive lengths of antenna wires, many kilometers long, at both the sending and receiving ends. The length of those sending and receiving wires needed to be about the same length as the width of the water (or land) that needed to be spanned. For example, for Preece's station to span the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
from Dover, England, to the coast of France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
would require sending and receiving wires of about 30 miles (50 kilometers) along the two coasts. These facts made it impractical to use Preece's system on either ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
s, boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...
s, or ordinary island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s (ones much smaller than Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
or Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
), and the relatively short distances that a practical Preece system could span meant that it had few advantages over underwater telegraph cables.
Period before 1838
In 1832, Lindsay gave a classroom demonstration of wireless telegraphy to his students. By 1854 he was able to demonstrate transmission across the Firth of TayFirth of Tay
The Firth of Tay is a firth in Scotland between the council areas of Fife, Perth and Kinross, the City of Dundee and Angus, into which Scotland's largest river in terms of flow, the River Tay, empties....
from Dundee to Woodhaven (now part of Newport-on-Tay), a distance of two miles (three kilometers).
Period 1838-1897
Wireless telegraphy dates as far back as FaradayMichael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
in the early 19th century, when it was discovered that radio waves could be used to send telegraph messages. After James Clerk Maxwell
James Clerk Maxwell
James Clerk Maxwell of Glenlair was a Scottish physicist and mathematician. His most prominent achievement was formulating classical electromagnetic theory. This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory...
had predicted the existence of electromagnetic waves, and had shown that their speed of propagation is identical with that of light, it required, in reality, very little to demonstrate by experiment the existence of such waves.
Calzecchi-Onesti
By 1884, Temistocle Calzecchi-OnestiTemistocle Calzecchi-Onesti
-References:* at radiomarconi.com* at browsebiography.com...
at Fermo
Fermo
Fermo is a town and comune of the Marche, Italy, in the Province of Fermo.Fermo is located on a hill, the Sabulo with a fine view, on a branch from Porto San Giorgio on the Adriatic coast railway....
in Italy developed a primitive device that responded to radio waves. It consisted of a tube filled with iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
filings, called a "coherer
Coherer
The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the twentieth century. Invented around 1890 by French scientist Édouard Branly, it consisted of a tube or capsule containing two electrodes spaced a...
". This kind of device would later be developed to become the first practical radio detector
Detector (radio)
A detector is a device that recovers information of interest contained in a modulated wave. The term dates from the early days of radio when all transmissions were in Morse code, and it was only necessary to detect the presence of a radio wave using a device such as a coherer without necessarily...
. Writing in the Rendiconti of the Lombardy Institution regarding the discovery of the coherer, directs attention to his experiments made in 1884, before Branly had worked on the subject. He further points out the part played by Augusto Righi
Augusto Righi
Augusto Righi was an Italian physicist and a pioneer in the study of electromagnetism. He was born and died in Bologna.His early research, conducted in Bologna between 1872 and 1880, was primarily in electrostatics...
in wireless telegraphy.
Edward Branly was preceded in the way he conducted his research by the Italian professor Temistocle Calzecchi-Onesti, who, 1884 and 1885 has the publiesed in Nuovo Cimento
Nuovo Cimento
Nuovo Cimento is a series of peer-reviewed scientific journals of physics. The series was first established in 1855 in Pisa, Italy, when Carlo Matteucci and Raffaele Piria started publishing Il Nuovo Cimento as the continuation of Il Cimento, which they founded in 1844...
results he obtained. The experience is typical Calzecchi interesting for the object at hand. Having placed a small quantity of filings copper between two pieces of brass, he found through a battery and a galvanometer that, depending on the degree of compaction, the powder was conductive or insulating and that the case presented some interesting features.
Circuit already including the filings tube and galvanometer Wiedemann, he added a phone and a mercury switch to eliminate at will the filings tube and the galvanometer and do replace them by a short circuit. This prepared, he noted, through the galvanometer, that the tube gave way to a very low current. He then introduced the short-circuit: a shock produced in the phone indicated the presence of current intense enough. Ending the short-circuit and restoring the tube and the galvanometer, he found that the tube had become a driver. It also showed that this effect was due to the extra current to begin opening in the coil of the phone. He verified the fact with various powders and found that some of them become conductive under the action of this simple spark of extra current, while others were changed by the more powerful action of static machines.
Experiments Calzecchi were not widely reported when they are published, not linked to any important issue to the agenda fell into oblivion. Mr. Hranly, which carefully outlined the work that touched on his own research when he published them, ignored them and it certainly took the controversy raised by the claims Marconi prissent the acute nature that they have acquired This memory was pulled from oblivion. He would later write, Le mie esperienze e di Edoardo quelle Branly Sulla conduttività elettrica delle limature metalliche.
Heinrich Hertz
Between 1886 and 1888, Heinrich Rudolf HertzHeinrich Rudolf Hertz
Heinrich Rudolf Hertz was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell...
studied Maxwell's theory and validated it through experiment. He demonstrated the transmission and reception of the electromagnetic waves predicted by Maxwell and intentionally transmitted and received radio. Hertz changed the frequency of his radiated waves by altering the inductance or capacity of his radiating conductor or antenna, and reflected and focused the electromagnetic waves, thus demonstrating the correctness of Maxwell's electromagnetic theory of light. Famously, he saw no practical use for his discovery.
In his UHF
Ultra high frequency
Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...
experiments, he transmitted and received radio waves over short distances and showed that the properties of radio waves were consistent with Maxwell’s electromagnetic theory. He demonstrated that radio radiation had all the properties of waves (now called electromagnetic radiation), and discovered that the electromagnetic equations could be reformulated into a partial differential equation
Partial differential equation
In mathematics, partial differential equations are a type of differential equation, i.e., a relation involving an unknown function of several independent variables and their partial derivatives with respect to those variables...
called the wave equation
Wave equation
The wave equation is an important second-order linear partial differential equation for the description of waves – as they occur in physics – such as sound waves, light waves and water waves. It arises in fields like acoustics, electromagnetics, and fluid dynamics...
.
Heinrich Hertz (1888) demonstrated the existence of electromagnetic radiation (radio waves) in a series of experiments in Germany during the 1880s. Hertz showed methods of producing, detecting, and measuring these waves. It had been known for many years, from the predictions of Kelvin and Von Helmholtz, and confirmed by the experiments of Fedderssen, that in many cases an electric discharge is of an oscillatory character. In the years 1887-8, Lodge, Fitzgerald, and others were investigating the nature of these oscillations, and the manner in which they are guided by conducting wires, when Hertz conceived the idea of investigating the disturbances which such oscillatory discharges set up in the surrounding space.
Hertz used the damped oscillating currents in a dipole antenna, triggered by a high-voltage electrical capacitive spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...
discharge, as his source of radio waves. His detector in some experiments was another dipole antenna connected to a narrow spark gap. A small spark in this gap
Spark gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the gap's breakdown voltage, a spark forms,...
signified detection of the radio waves. When he added cylindrical reflectors behind his dipole antennas, Hertz could detect radio waves about 20 metres from the transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
in his laboratory
Laboratory
A laboratory is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. The title of laboratory is also used for certain other facilities where the processes or equipment used are similar to those in scientific laboratories...
. He did not try to transmit further because he wanted to prove electromagnetic theory
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
, not to develop wireless communication
Communication
Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...
s.
In the collection of physical instruments at the Technical High School
Karlsruhe Institute of Technology
The Karlsruhe Institute of Technology is a German academic research and education institution with university status resulting from a merger of the university and the research center of the city of Karlsruhe. The university, also known as Fridericiana, was founded in 1825...
at Karlsruhe
Karlsruhe
The City of Karlsruhe is a city in the southwest of Germany, in the state of Baden-Württemberg, located near the French-German border.Karlsruhe was founded in 1715 as Karlsruhe Palace, when Germany was a series of principalities and city states...
(where these researches were carried out), Hertz had found and used for lecture purposes a pair of so-called Eiess spirals or Knochenhauer spirals. Hertz had been surprised to find that it was not necessary to discharge large batteries through one of these spirals in order to obtain sparks in the other; that small Leyden jar
Leyden jar
A Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a jar. It was invented independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist Pieter van Musschenbroek of Leiden in 1745–1746. The...
s amply sufficed for this purpose, and that even the discharge of a small induction coil
Induction coil
An induction coil or "spark coil" is a type of disruptive discharge coil. It is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current supply...
would do, provided it had to spring across a spark gap. In altering the conditions Hertz came upon the phenomenon of side-sparks, which formed the starting point of his research. At first Hertz thought the electrical disturbances would be too turbulent and irregular to be of any further use, but when he had discovered the existence of a neutral point in the middle of a side-conductor, and therefore of a clear and orderly phenomenon, he felt convinced that the problem of the Berlin Academy was now capable of solution. His ambition at the time did not go further than this. Hertz's conviction was naturally strengthened by finding that the oscillations with which he had to deal were regular.
Hertz’s setup for a source and detector of radio waves (then called Hertzian waves in his honor) was the first intentional and unequivocal transmission and reception of radio waves
Radio waves
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...
through free space
Free-space optical communication
Free-space optical communication is an optical communication technology that uses light propagating in free space to transmit data for telecommunications or computer networking."Free space" means air, outer space, vacuum, or something similar...
. The first of the papers published ("On Very Rapid Electric Oscillations") gives, generally in the actual order of time, the course of the investigation as far as it was carried out up to the end of the year 1886 and the beginning of 1887.
Hertz, though, did not devise a system for actual general use nor describe the application of the technology and seemed uninterested in the practical importance of his experiments. He stated that "It's of no use whatsoever ... this is just an experiment that proves Maestro Maxwell was right — we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there."
Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess." Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application." Hertz died in 1894, so the art of radio was left to others to implement into a practical form.
Branly
In 1890, Édouard BranlyEdouard Branly
Édouard Eugène Désiré Branly was a French inventor, physicist and professor at the Institut Catholique de Paris. He is primarily known for his early involvement in wireless telegraphy and his invention of the Branly coherer around 1890.-Biography:The coherer was the first widely used detector for...
demonstrated what he later called the "radio-conductor," which Lodge in 1893 named the coherer
Coherer
The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the twentieth century. Invented around 1890 by French scientist Édouard Branly, it consisted of a tube or capsule containing two electrodes spaced a...
, the first sensitive device for detecting radio waves. Shortly after the experiments of Hertz, Dr. Branly discovered that loose metal filings, which in a normal state have a high electrical resistance, lose this resistance in the presence of electric oscillations and become practically conductors of electricity. This Branly showed by placing metal filings in a glass box or tube, and making them part of an ordinary electric circuit. According to the common explanation, when electric waves are set up in the neighborhood of this circuit, electromotive forces are generated in it which appear to bring the filings more closely together, that is, to cohere, and thus their electrical resistance decreases, from which cause this piece of apparatus was termed by Sir Oliver Lodge a coherer. Hence the receiving instrument, which may be a telegraph relay, that normally would not indicate any sign of current from the small battery, can be operated when electric oscillations are set up. Prof. Branly further found that when the filings had once cohered they retained their low resistance until shaken apart, for instance, by tapping on the tube.
In On the Changes in Resistance of Bodies under Different Electrical Conditions, he described how the electrical circuit was made by means of two narrow strips of copper parallel to the short sides of the rectangular plate, and forming good contact with it by means of screws. When the two copper strips were raised the plate was cut out of the circuit. He also used as conductors fine metallic filings, which he sometimes mixed with insulating liquids. The filings were placed in a tube of glass or ebonite
Ebonite
Ebonite is a brand name for very hard rubber first obtained by Charles Goodyear by vulcanizing rubber for prolonged periods. It is about 30% to 40% sulfur. Its name comes from its intended use as an artificial substitute for ebony wood...
, and were held between two metal plates. When the electrical circuit, consisting of a Daniell cell
Daniell cell
The Daniell cell was invented in 1836 by John Frederic Daniell, a British chemist and meteorologist, and consisted of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode...
, a galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
of high resistance, and the metallic conductor, consisting of the ebonite plate, and the sheet of copper, or of the tube containing the filings, was completed, only a very small current flowed; but there was a sudden diminution of the resistance which was proved by a large deviation of the galvanometer
Galvanometer
A galvanometer is a type of ammeter: an instrument for detecting and measuring electric current. It is an analog electromechanical transducer that produces a rotary deflection of some type of pointer in response to electric current flowing through its coil in a magnetic field. .Galvanometers were...
needle when one or more electric discharges were produced in the neighbourhood of the circuit. In order to produce these discharges a small Wimshurst influence machine was used, with or without a condenser, or a Ruhmkorff coil. The action of the electrical discharge diminished as the distance increases; but he observed it easily, and without taking any special precautions, at a distance of several yards. By using a Wheatstone bridge
Wheatstone bridge
A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and...
, he observed this action at a distance of 20 yards, although the machine producing the sparks was working in a room separated from the galvanometer and the bridge by three large apartments, and the noise of the sparks was not audible. The changes of resistance were considerable with the conductors described. They varied, for instance, from several millions of ohms to 2000, or even to 100, from 150,000 to 500 ohms, from 50 to 35, and so on. The diminution of resistance was not momentary, and sometimes it was found to remain for twenty-four hours. Another method of making the test was, by connecting the electrodes of a capillary electrometer to the two poles of a Daniell cell with a sulphate of cadmium solution. The displacement of mercury which took place when the cell was short-circuited, only took place very slowly when an ebonite plate, covered with a sheet of copper of high resistance, was inserted between one of the poles of the cell, and the corresponding electrode of the electrometer; but when sparks were produced by a machine, the mercury was rapidly thrown into the capillary tube owing to the sudden diminution in the resistance of the plate.
Branly found that, upon examination of the conditions necessary to produce the phenomena, the following data:
- The circuit need not be closed to produce the result.
- The passage of an induced current in the body produces a similar effect to that of a spark at a distance.
- An induction-coil with two equal lengths of wire was used, a current is sent through the primary while the secondary forms part of a circuit containing the tube with filings and a galvanometer. The two induced currents caused the resistance of the filings to vary.
- When working with continuous currents the passage of a strong current lowers the resistance of the body for feeble currents.
Summing up, he stated that in all these tests the use of ebonite plates covered with copper or mixtures of copper and tin was less satisfactory than the use of filings; with the plates he was unable to obtain the initial resistance of the body after the action of the spark or of the current, while with the tubes and filings the resistance could be brought back to its normal value by striking a few sharp blows on the support of the tube.
The disadvantages of the coherer are it is erratic nature in its sensitiveness, which may be much decreased by local discharges, such as the spark discharges of the transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
, and it responds to atmospheric disturbances or lightning discharges. Consequently, the coherer cannot be relied upon as a calling-up apparatus. With strong impulses of energy in the receiver it enables one to print the received message, but for long-distance work it is not as sensitive as some other detectors which are of more developed in the inter-war period before the roaring Twenties
Roaring Twenties
The Roaring Twenties is a phrase used to describe the 1920s, principally in North America, but also in London, Berlin and Paris for a period of sustained economic prosperity. The phrase was meant to emphasize the period's social, artistic, and cultural dynamism...
.
de Moura
Roberto Landell de Moura, a Brazilian priest and scientist, went to Rome in 1878 and studied at the South American CollegeSouth American College in Rome
The South American College in Rome is one of the Roman Colleges of the Roman Catholic Church, for students from Central and South America.-History:...
and Pontifical Gregorian University
Pontifical Gregorian University
The Pontifical Gregorian University is a pontifical university located in Rome, Italy.Heir of the Roman College founded by Saint Ignatius of Loyola over 460 years ago, the Gregorian University was the first university founded by the Jesuits...
, where he studied physics and chemistry. He completed his clerical training in Rome, graduating in theology and was ordained priest in 1886. In Rome, he started studying physics and electricity. When he returned to Brazil, he conducted experiments in wireless in Campinas
Campinas
Campinas is a city and municipality located in the coastal interior of the state of São Paulo, Brazil. is the administrative center of the meso-region of the same name, with 3,783,597 inhabitants as of the 2010 Census, consisting of 49 cities....
and São Paulo
São Paulo
São Paulo is the largest city in Brazil, the largest city in the southern hemisphere and South America, and the world's seventh largest city by population. The metropolis is anchor to the São Paulo metropolitan area, ranked as the second-most populous metropolitan area in the Americas and among...
(1892–1893). In the "Porto Jornal da Manha", he is said to have conducted between 1890 and 1894 wireless transmissions in telegraphy and telephony over distances of up to 8 kilometres (5 mi).
Tesla
In St. LouisSt. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
, Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
, Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
made the first public demonstration of a modern wireless system in 1893. Addressing the Franklin Institute
Franklin Institute
The Franklin Institute is a museum in Philadelphia, Pennsylvania, and one of the oldest centers of science education and development in the United States, dating to 1824. The Institute also houses the Benjamin Franklin National Memorial.-History:On February 5, 1824, Samuel Vaughn Merrick and...
in Philadelphia and the National Electric Light Association
National Electric Light Association
The National Electric Light Association was a national United States trade association including the operators of central power generation stations and interested individuals. Founded in 1885 by G. S. Bowen Terry and Charles A. Brown, it represented the interests of various private companies...
, he described and demonstrated in detail the principles of wireless telegraphy and radio. The apparatus that he used contained all the elements that were incorporated into radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
systems before the development of the vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
. This led to work in using radio signals for wireless communication, initially with limited success. Using spark-gap transmitters plus coherer-receivers were tried by many experimenters, but several were unable to achieve transmission ranges of more than a few hundred metres. This was not the case for all researchers in the field of the wireless arts, though.
In 1891, Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
began his research into radio. Around July 1891, Tesla developed various alternator apparatus
Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...
that produced 15,000 cycles per second
Very low frequency
225px|thumb|right|A VLF receiving antenna at [[Palmer Station]], Antarctica, operated by Stanford UniversityVery low frequency or VLF refers to radio frequencies in the range of 3 kHz to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals...
. In 1892 he gave a lecture called "Experiments with Alternate Currents of High Potential and High Frequency". Tesla delivered the presentation before the Institution of Electrical Engineers
Institution of Electrical Engineers
The Institution of Electrical Engineers was a British professional organisation of electronics, electrical, manufacturing, and Information Technology professionals, especially electrical engineers. The I.E.E...
of London (February 3, 1892) in which he suggested that messages could be transmitted without wires. He repeated this to the Royal Institution
Royal Institution
The Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London.-Overview:...
(February 4, 1892). He would again repeat the presentation to the Société Française de Physique (February 19, 1892) in Paris. Tesla realized he gained, by the use of very high frequencies, many advantages in his experiments, such as the possibility of working with one lead and the possibility of doing away with the leading-in wire. In transmitting impulses through conductors, he dealt with high pressure and high flow, in the ordinary interpretation of these terms. Towards the end of the lecture, he proposed that sending over the wire current vibrations of very high frequencies at enormous distance without affecting greatly the character of the vibrations and that telephony could be rendered practicable across the Atlantic. He also proposed that intelligence — transmitted without wires — transmission through the Earth and to establish the physical mechanism of such a circuit. Tesla captured the attention of the whole scientific world by his fascinating experiments on high frequency electric currents. He stimulated the scientific imagination of others as well as displayed his own, and created a widespread interest in his brilliant demonstrations. Accordingly there are seven elements in the complete oscillation-producing appliance, which are as follows:
- The induction coil transformer or source of electromotive forceElectromotive forceIn physics, electromotive force, emf , or electromotance refers to voltage generated by a battery or by the magnetic force according to Faraday's Law, which states that a time varying magnetic field will induce an electric current.It is important to note that the electromotive "force" is not a...
. - The condenserCapacitorA capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
. - The dischargerDischargerA discharger in electronics is a device or circuit that releases stored energy or electric charge from a battery, capacitor or other source.Discharger types include:* metal probe with insulated handle & ground wire, and sometimes resistor...
or spark ballSpark gapA spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the voltage difference between the conductors exceeds the gap's breakdown voltage, a spark forms,...
s. - The arc quenching inductances.
- The oscillation transformer.
- The adjustable inductance for varying the period.
- The controller or keyTelegraph keyTelegraph key is a general term for any switching device used primarily to send Morse code. Similar keys are used for all forms of manual telegraphy, such as in electrical telegraph and radio telegraphy.- Types of keys :...
in the primary circuit of the coil or transformer.
These several elements have each to be considered separately with reference to their best practical forms for various purposes. When the key is closed, and the apparatus in operation, there are trains of intermittent electrical oscillations set up in the circuit, and if the terminals of the secondary circuit of the oscillation transformer are near together, there is high potential high frequency oscillatory sparks passing between them. The above-described apparatus in a typical form is generally called a Tesla apparatus for the production of high frequency electric currents.
"On Light and Other High Frequency Phenomena" |
In 1893, at St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
, Tesla gave a public demonstration, "On Light and Other High Frequency Phenomena", of wireless communication. Addressing the Franklin Institute
Franklin Institute
The Franklin Institute is a museum in Philadelphia, Pennsylvania, and one of the oldest centers of science education and development in the United States, dating to 1824. The Institute also houses the Benjamin Franklin National Memorial.-History:On February 5, 1824, Samuel Vaughn Merrick and...
in Philadelphia, he described in detail the principles of early radio communication. The lecture apparatus that Tesla used contained all the elements that were incorporated into radio systems before the development of the "oscillation valve", the early vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
. The lecture delivered before the Franklin Institute, at Philadelphia, occurred on February 24, 1893. The variety of Tesla's radio frequency systems were again demonstrated during when he presented to meetings of the National Electric Light Association
National Electric Light Association
The National Electric Light Association was a national United States trade association including the operators of central power generation stations and interested individuals. Founded in 1885 by G. S. Bowen Terry and Charles A. Brown, it represented the interests of various private companies...
, at St. Louis, on March I, 1893. Afterward, the principle of radio communication (sending signals through space to receivers) was publicized widely from Tesla's experiments and demonstrations. On August 25, 1893, Tesla delivered the lecture "Mechanical and Electrical Oscillators", before the International Electrical Congress, in the hall adjoining the Agricultural Building, at the World's Fair, Chicago
World's Columbian Exposition
The World's Columbian Exposition was a World's Fair held in Chicago in 1893 to celebrate the 400th anniversary of Christopher Columbus's arrival in the New World in 1492. Chicago bested New York City; Washington, D.C.; and St...
. This helped popularize radio communication activity worldwide, which is covered in depth by Invention of Radio
Invention Of Radio
Within the history of radio, several people were involved in the invention of radio and there were many key inventions in what became the modern systems of wireless. Radio development began as "wireless telegraphy"...
and History of Radio
History of radio
The early history of radio is the history of technology that produced radio instruments that use radio waves. Within the timeline of radio, many people contributed theory and inventions in what became radio. Radio development began as "wireless telegraphy"...
.
The high-frequency phenomena which Tesla first developed and displayed had scientific rather than practical interest; but Tesla called attention to the fact that by taking the Tesla oscillator, grounding one side of it and connecting the other to an insulated body of large surface, it should be possible to transmit electric oscillations to a great distance, and to communicate intelligence in this way to other oscillators in sympathetic resonance therewith. This was going far toward the invention of radio-telegraphy as then known.
Transmission and radiation of radio frequency energy was a feature exhibited in the experiments by Tesla which he proposed might be used for the telecommunication
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
of information
Information
Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
. The Tesla method
Wireless energy transfer
Wireless energy transfer or wireless power is the transmission of electrical energy from a power source to an electrical load without artificial interconnecting conductors. Wireless transmission is useful in cases where interconnecting wires are inconvenient, hazardous, or impossible...
was described in New York in 1897.
Thomas Commerford Martin
Thomas Commerford Martin was an American electrical engineer and editor, born in London, England. His father worked with Lord Kelvin and other pioneers of submarine telegraph cables, and Martin spent much time on the cable-laying ship SS Great Eastern. Educated as a theological student, Martin...
publishes "The Inventions, Researches and Writings of Nikola Tesla", detailing the work of Tesla in the previous years. Various scientists, inventors, and experimenters began to investigate wireless methods. Telsa's work contained coupled oscillation circuits having capacity and inductance in series. In 1897, Tesla applied for two key United States radio patents, , first radio system patent, and . Tesla also used sensitive electromagnetic receivers, that were unlike the less responsive coherer
Coherer
The coherer was a primitive form of radio signal detector used in the first radio receivers during the wireless telegraphy era at the beginning of the twentieth century. Invented around 1890 by French scientist Édouard Branly, it consisted of a tube or capsule containing two electrodes spaced a...
s later used by Marconi and other early experimenters. Shortly thereafter, he began to develop wireless remote control devices.
Marconi
By 1897, Guglielmo MarconiGuglielmo Marconi
Guglielmo Marconi was an Italian inventor, known as the father of long distance radio transmission and for his development of Marconi's law and a radio telegraph system. Marconi is often credited as the inventor of radio, and indeed he shared the 1909 Nobel Prize in Physics with Karl Ferdinand...
conducted a series of demonstrations with a radio system for signalling for communications over long distances
Marconi's law
Marconi's law is the relation between height of antennae and maximum signalling distance. Guglielmo Marconi enunciated at one time an empirical law that, for simple vertical sending and receiving antennae of equal height, the maximum working telegraphic distance varied as the square of the height...
. Marconi is said to have read, while on vacation in 1894, about the experiments that Hertz did in the 1880s. Marconi also read about Tesla's work. It was at this time that Marconi began to understand that radio waves could be used for wireless communications. Marconi's early apparatus was a development of Hertz’s laboratory apparatus into a system designed for communications purposes. At first Marconi used a transmitter to ring a bell in a receiver in his attic laboratory. He then moved his experiments out-of-doors on the family estate near Bologna, Italy, to communicate farther. He replaced Hertz’s vertical dipole with a vertical wire topped by a metal sheet, with an opposing terminal connected to the ground. On the receiver side, Marconi replaced the spark gap with a metal powder coherer, a detector developed by Edouard Branly
Edouard Branly
Édouard Eugène Désiré Branly was a French inventor, physicist and professor at the Institut Catholique de Paris. He is primarily known for his early involvement in wireless telegraphy and his invention of the Branly coherer around 1890.-Biography:The coherer was the first widely used detector for...
and other experimenters. Marconi transmitted radio signals for about a mile at the end of 1895.
By 1896, Marconi introduced to the public a device in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, asserting it was his invention. Despite Marconi's statements to the contrary, though, the apparatus resembles Tesla's descriptions in his research, demonstrations and patents. Marconi's later practical four-tuned system was pre-dated by N. Tesla, Oliver Lodge, and J. S. Stone. He filed a patent on his earliest system with the British Patent Office on June 2, 1896.
In 1897, Marconi was awarded a patent for radio with British patent No. 12,039, Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for. The complete specification was filed March 2, 1897. This was Marconi's initial patent for the radio, though it used various earlier techniques of various other experimenters (primarily Tesla) and resembled the instrument demonstrated by others (including Popov). During this time spark-gap wireless telegraphy was widely researched. In July, 1896, Marconi got his invention and new method of telegraphy to the attention of Preece, then engineer-in-chief to the British Government Telegraph Service, who had for the previous twelve years interested himself in the development of wireless telegraphy by the inductive-conductive method. On June 4, 1897, he delievers "Signalling through Space without Wires". Preece devoted considerable time to exhibiting and explaining the Marconi apparatus at the Royal Institution
Royal Institution
The Royal Institution of Great Britain is an organization devoted to scientific education and research, based in London.-Overview:...
in London, stating that Marconi invented a new relay which had high sensitiveness and delicacy.
In 1896, Jagdish Chandra Bose
Jagdish Chandra Bose
Acharya Sir Jagadish Chandra Bose, CSI, CIE, FRS was a Bengali polymath: a physicist, biologist, botanist, archaeologist, as well as an early writer of science fiction...
went to London on a lecture tour and met Marconi, who was conducting wireless experiments for the British post office. The Marconi Company Ltd. was founded by Marconi in 1897, known as the Wireless Telegraph Trading Signal Company. Also in 1897, Marconi established the radio station at Niton, Isle of Wight
Niton, Isle of Wight
Niton is a village on the Isle of Wight, near Ventnor with a thriving population of 1142, supporting two pubs, several churches,a pottery workshop/shop, a pharmacy and 3 local shops including a post office...
, England. Marconi's wireless telegraphy was inspected by the Post Office Telegraph authorities; they made a series of experiments with Marconi's system of telegraphy without connecting wires, in the Bristol Channel
Bristol Channel
The Bristol Channel is a major inlet in the island of Great Britain, separating South Wales from Devon and Somerset in South West England. It extends from the lower estuary of the River Severn to the North Atlantic Ocean...
. The October wireless signals of 1897 were sent from Salisbury Plain
Salisbury Plain
Salisbury Plain is a chalk plateau in central southern England covering . It is part of the Southern England Chalk Formation and largely lies within the county of Wiltshire, with a little in Hampshire. The plain is famous for its rich archaeology, including Stonehenge, one of England's best known...
to Bath, a distance of thirty-four miles. Marconi's reputation is largely based on the making of his law
Marconi's law
Marconi's law is the relation between height of antennae and maximum signalling distance. Guglielmo Marconi enunciated at one time an empirical law that, for simple vertical sending and receiving antennae of equal height, the maximum working telegraphic distance varied as the square of the height...
(1897), and other accomplishments in radio communications and commercializing a practical system.
Other experimental stations were established at Lavernock Point, near Penarth
Penarth
Penarth is a town and seaside resort in the Vale of Glamorgan , Wales, 5.2 miles south west from the city centre of the Welsh capital city of Cardiff and lying on the north shore of the Severn Estuary at the southern end of Cardiff Bay...
; on the Flat Holmes, an island in mid-channel, and at Brean Down
Brean Down
Brean Down is a promontory off the coast of Somerset standing high and extending into the Bristol Channel at the eastern end of Bridgwater Bay between Weston-super-Mare and Burnham-on-Sea....
, a promontory
Promontory
Promontory may refer to:*Promontory, a prominent mass of land which overlooks lower lying land or a body of water*Promontory, Utah, the location where the United States first Transcontinental Railroad was completed...
on the Somerset
Somerset
The ceremonial and non-metropolitan county of Somerset in South West England borders Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west. It is partly bounded to the north and west by the Bristol Channel and the estuary of the...
side. Signals were obtained between the first and last-named points, a distance of, approximately, eight miles. The receiving instrument used was a Morse inkwriter of the Post Office pattern.
Period 1898-1902
The term Wireless Telegraphy came into widespread use around the turn of the previous century when Spark-gap transmitterSpark-gap transmitter
A spark-gap transmitter is a device for generating radio frequency electromagnetic waves using a spark gap.These devices served as the transmitters for most wireless telegraphy systems for the first three decades of radio and the first demonstrations of practical radio were carried out using them...
s and primitive receivers made it practical to send telegraph messages over great distances, enabling transcontinental and ship-to-shore signalling. Before that time, wireless telegraphy was an obscure experimental term that applied collectively to an assortment of sometimes unrelated signalling schemes. In 1898, Tesla demonstrated a radio controlled boat in Madison Square Garden
Madison Square Garden (1890)
Madison Square Garden was an indoor arena in New York City, the second by that name, and the second to be located at 26th Street and Madison Avenue in Manhattan...
that allowed secure communication
Secure communication
When two entities are communicating and do not want a third party to listen in, they need to communicate in a way not susceptible to eavesdropping or interception. This is known as communicating in a secure manner or secure communication...
between transmitter and receiver.
In 1899, de Moura transmitted the human voice from the College of the Sisters of St. Joseph
Sisters of St. Joseph
The title Sisters of St. Joseph applies to several Roman Catholic religious congregations of women. The largest and oldest of these was founded in Le Puy-en-Velay, France...
, high in the district of Santana, Brazil, north of the capital city. Also made public demonstrations of his invention on June 3, 1900, being reported by the Jornal do Commercio (June 10, 1900), "Last Sunday, on top of Santana in São Paulo , Padre Landell de Moura has particular experience with various devices of his invention. In order to demonstrate some laws which he discovered in studying the propagation of sound, the light and electricity through space, which were crowned with brilliant success." The experiences were performed in the presence of the English Vice Consul S. Paul, Percy Parmenter, Charles Lupton
Charles Lupton
Captain Charles Roger Lupton was a World War I flying ace credited with five aerial victories.-References:...
, and other persons of high social position. Upon observing the experiments, Rodriguez Botet, giving news of the trials, said he was not far from the moment of the consecration of Landell as an author of radio discoveries. The wireless telephony is reputed the most important discoveries of Landell. De Moura did later pursue and receive several patents on wireless technology. He would later obtain for a wireless telephone.
In 1898, Marconi opened a radio factory in Hall Street, Chelmsford, England, employing around 50 people. In 1899, Marconi announced his invention of the "iron-mercury-iron coherer with telephone detector" in a paper presented at Royal Society, London. In May, 1898, communication was established for the Corporation of Lloyds
Lloyd's of London
Lloyd's, also known as Lloyd's of London, is a British insurance and reinsurance market. It serves as a partially mutualised marketplace where multiple financial backers, underwriters, or members, whether individuals or corporations, come together to pool and spread risk...
between Ballycastle
Ballycastle, County Antrim
Ballycastle is a small town in County Antrim in Northern Ireland. Its population was 5,089 people in the 2001 Census. It is the seat and main settlement of Moyle District Council....
and the Lighthouse
Lighthouse
A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses or, in older times, from a fire, and used as an aid to navigation for maritime pilots at sea or on inland waterways....
on Rathlin Island
Rathlin Island
Rathlin Island is an island off the coast of County Antrim, and is the northernmost point of Northern Ireland. Rathlin is the only inhabited offshore island in Northern Ireland, with a rising population of now just over 100 people, and is the most northerly inhabited island off the Irish coast...
in the North of Ireland. In July, 1898, the Marconi telegraphy was employed to report the results of yacht races at the Kingston Regatta
Kingston Regatta
Kingston Regatta is a rowing regatta, on the River Thames in England which takes place at Kingston upon Thames, Surrey on the reach above Teddington Lock....
for the Dublin Express
Daily Express (Dublin)
The Daily Express of Dublin was an Irish newspaper published from 1851 until June 1921, and then continued for registration purposes until 1960.It was a unionist newspaper. From 1917, its title was the Daily Express and Irish Daily Mail...
newspaper. A set of instruments were fitted up in a room at Kingstown, and another on board a steamer, the Flying Huntress. The aerial conductor on shore was a strip of wire netting attached to a mast 40 feet high, and several hundred messages were sent and correctly received during the progress of the races.
At this time His Majesty King Edward VII, then Prince of Wales
Prince of Wales
Prince of Wales is a title traditionally granted to the heir apparent to the reigning monarch of the United Kingdom of Great Britain and Northern Ireland and the 15 other independent Commonwealth realms...
, had the misfortune to injure his knee, and was confined on board the royal yacht Osltorm in Cowes Bay.
Marconi fitted up his apparatus on board the royal yacht by request, and also at Osborne House
Osborne House
Osborne House is a former royal residence in East Cowes, Isle of Wight, UK. The house was built between 1845 and 1851 for Queen Victoria and Prince Albert as a summer home and rural retreat....
, Isle of Wight, and kept up wireless communication for three weeks between these stations. The distances covered were small; but as the yacht moved about, on some occasions high hills were interposed, so that the aerial wires were overtopped by hundreds of feet, yet this was no obstacle to communication. These demonstrations led the Corporation of Trinity House to afford an opportunity for testing the system in practice between the South Foreland Lighthouse
South Foreland Lighthouse
South Foreland Lighthouse is a Victorian lighthouse on the South Foreland in St. Margaret's Bay, Dover, Kent, England, used to warn ships approaching the nearby Goodwin Sands. It went out of service in 1988 and is currently owned by the National Trust...
, near Dover, and the East Goodwin Lightship, on the Goodwin Sands
Goodwin Sands
The Goodwin Sands is a 10-mile-long sand bank in the English Channel, lying six miles east off Deal in Kent, England. The Brake Bank lying shorewards is part of the same geological unit. As the shoals lie close to major shipping channels, more than 2,000 ships are believed to have been wrecked...
. This installation was set in operation on December 24, 1898, and proved to be of value. It was shown that when once the apparatus was set up it could be worked by ordinary seamen with very little training.
At the end of 1898 electric wave telegraphy established by Marconi had demonstrated its utility, especially for communication between ship and ship and ship and shore. The Haven Hotel
Haven Hotel
The Haven Hotel is an AA four star hotel in Sandbanks, near Poole, Dorset on the south coast of England.-History:The first hotel built on this location was the North Haven Inn in 1838. The Inn was demolished and replaced with the present Haven Hotel in 1887...
station and Wireless Telegraph Mast was where much of Marconi's research work on wireless telegraphy was carried out after 1898. In 1899, W. H. Preece delivers "Aetheric Telegraphy", stating that the experimental stage in wireless telegraphy had been passed in 1894 and inventors were then entering the commercial stage. Preece, continuing in the lecture, details the work of Marconi and other British inventors. The Marconi Company was renamed Marconi's Wireless Telegraph Company in 1900. In 1899 he transmitted messages across the English Channel
English Channel
The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...
. The British Navy experiments with Marconi's system in the Anglo-Boer War from 1899-1902 was the first use of operational wireless telegraphy in the field.
Medium frequency
Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
(820 kHz). Marconi established a wireless transmitting station at Marconi House, Rosslare Strand, Co. Wexford in 1901 to act as a link between Poldhu in Cornwall and Clifden in Co. Galway. His announcement on 12 December 1901, using a 152.4 metres (500 ft) kite-supported antenna for reception, stated a the message was received at Signal Hill in St John's
St. John's, Newfoundland and Labrador
St. John's is the capital and largest city in Newfoundland and Labrador, and is the oldest English-founded city in North America. It is located on the eastern tip of the Avalon Peninsula on the island of Newfoundland. With a population of 192,326 as of July 1, 2010, the St...
, Newfoundland
Newfoundland and Labrador
Newfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...
(now part of Canada) via signals transmitted by the company's new high-power station at Poldhu
Poldhu
Poldhu is a small area in south Cornwall, England, UK, situated on the Lizard Peninsula; it comprises Poldhu Point and Poldhu Cove. It lies on the coast west of Goonhilly Downs, with Mullion to the south and Porthleven to the north...
, Cornwall
Cornwall
Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...
. The message received was the Morse letter 'S' - three dots. Bradford has recently contested this, however, based on theoretical work as well as a reenactment of the experiment; it is possible that what was heard was only random atmospheric noise, which was mistaken for a signal, or that Marconi may have heard a shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
of the signal. The distance between the two points was about 3500 kilometres (2,174.8 mi).
Marconi transmitted from England to Canada and the United States. In 1902, a Marconi station
Marconi Station
The Marconi Wireless Corporation operated numerous pioneering radio stations in Canada, Ireland, Newfoundland, the United States, the United Kingdom and a number of other locations around the world.-Australia:...
was established in the village of Crookhaven
Crookhaven
Crookhaven is a village in County Cork, Ireland, on the most southwestern tip of Ireland. A winter population of about forty swells in the summer to about four hundred with the occupants of the many holiday homes arriving.-History:...
, County Cork
County Cork
County Cork is a county in Ireland. It is located in the South-West Region and is also part of the province of Munster. It is named after the city of Cork . Cork County Council is the local authority for the county...
, Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
to provide marine radio communications to ships arriving from the Americas. A ship's master could contact shipping line agents ashore to enquire which port was to receive their cargo without the need to come ashore at what was the first port of landfall. Ireland was also, due to its western location, to play a key role in early efforts to send trans-Atlantic messages. Marconi transmitted from his station in Glace Bay, Nova Scotia, Canada across the Atlantic, and on 18 January 1903 a Marconi station sent a message of greetings from Theodore Roosevelt
Theodore Roosevelt
Theodore "Teddy" Roosevelt was the 26th President of the United States . He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his "cowboy" persona and robust masculinity...
, the President of the United States, to the King of the United Kingdom, marking the first transatlantic radio transmission originating in the United States.
Period After 1902
In the early 20th century Jozef MurgasJozef Murgaš
Jozef Murgaš was a Slovak inventor, architect, botanist, painter, patriot, and Roman Catholic priest...
, the "Radio Priest", conducted a great deal of revolutionary work in wireless telegraphy. He established a laboratory in Wilkes-Barre, in which he primarily investigated radiotelegraphy. His article in the Tovaryšstvo magazine of 1900 shows that his radiotelegraphy studies had achieved a high level. In 1904, he received his first two US patents: the Apparatus for wireless telegraphy and The way of transmitted messages by wireless telegraphy. Further 11 patents followed between 1907 and 1911. Based on the first two patents, he created the Universal ether Telegraph Co., which organized a public test of Murgaš's transmitting and receiving facilities in September 1905. The test was successful, but a storm destroyed the antenna masts three month later, which led to a dissolution of the company.
In 1906, Lee De Forest
Lee De Forest
Lee De Forest was an American inventor with over 180 patents to his credit. De Forest invented the Audion, a vacuum tube that takes relatively weak electrical signals and amplifies them. De Forest is one of the fathers of the "electronic age", as the Audion helped to usher in the widespread use...
brought out a vacuum tube device which he called the "audion
Audion
An Audion is a wireless signal detector device invented by Lee De Forest in 1906.Audion may also refer to:* Audion , an electronic music album by Larry Fast* Audion , a media player for Apple Macintosh created by Panic...
" and which has been described in the A.I.E.E. Transactions. This was a very sensitive detector of electric oscillations and consisted of three electrodes in an exhausted envelope. One of the electrodes could be heated to incandescence with the result that electrons were emitted by it (the Edison effect).
When the United States entered World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
, private radiotelegraphy stations were prohibited, which put an end to several pioneer's work in this field. By the 1920s, there was a worldwide network of commercial and government radiotelegraphic stations, plus extensive use of radiotelegraphy by ships for both commercial purposes and passenger messages. The ultimate implementation of wireless telegraphy was telex
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
using radio signals, which was developed in the 1930s and was for many years the only reliable form of communication between many distant countries. The most advanced standard, CCITT
ITU-T
The ITU Telecommunication Standardization Sector is one of the three sectors of the International Telecommunication Union ; it coordinates standards for telecommunications....
R.44, automated both routing and encoding of messages by short wave transmissions. (See telegraphy
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
for more information).
Methods, apparatus, and operation
In De Forest method. a battery connected between this electrode, as cathode, and another as anode resulted in a convection current of electrons from one to the other. Since negative electricity only was present, current could flow in but one direction. This is so far the action of the Fleming valve which also makes use of the Edison effect, but in the audion an epoch making advance was made in that the third electrode allows us to completely control the strength of the electron current without consuming appreciable energy at that electrode or in its circuit. In other words an inappreciable amount of power applied to the third electrode, or grid, will result in large changes in power in the anode circuit. Moreover, since the electrons have no appreciable inertia, the response in the anode circuit to stimuli in the grid circuit is practically instantaneous.See also
- TelegraphyTelegraphyTelegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
- Electrical telegraphElectrical telegraphAn electrical telegraph is a telegraph that uses electrical signals, usually conveyed via telecommunication lines or radio. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages....
- Marconi Wireless Company
- American Telephone and Telegraph Company
- Imperial Wireless ChainImperial Wireless ChainThe Imperial Wireless Chain, also known as the Empire Wireless Chain, was a strategic international wireless telegraphy communications network, created to link the countries of the British Empire. Although the idea was conceived prior to World War I, Britain was the last of the world's Great Powers...
- Reginald FessendenReginald FessendenReginald Aubrey Fessenden , a naturalized American citizen born in Canada, was an inventor who performed pioneering experiments in radio, including early—and possibly the first—radio transmissions of voice and music...
Known for Inventing the Radiotelephony
Further reading
Listed by date [latest to earliest]- Sarkar, T. K., & Baker, D. C. (2006). History of wireless. Hoboken, NJ: Wiley-Interscience.
- Hugh G. J. Aitken, Syntony and Spark: the Origins of Radio, ISBN 0-471-01816-3. 1976.
- Elliot N. Sivowitch, A Technological Survey of Broadcasting’s Pre-History, Journal of Broadcasting, 15:1-20 (Winter 1970-71).
- Colby, F. M., Williams, T., & Wade, H. T. (1930). "Wireless Telegraphy", The New international encyclopaedia. New York: Dodd, Mead and Co.
- "Wireless telegraphy", The Encyclopaedia Britannica. (1922). London: Encyclopædia Britannica.
- Stanley, R. (1919). Text-book on wireless telegraphy. London: Longmans, Green
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- Massie, W. W., & Underhill, C. R. (1911). Wireless telegraphy and telephony popularly explained. New York: D. Van Nostrand.
- Captain S.S. Robison(1911). Developments in Wireless Telegraphy. International marine engineering, Volume 16. Simmons-Boardman Pub. Co.
- Bottone, S. R. (1910). Wireless telegraphy and Hertzian waves. London: Whittaker & Co.
- Erskine-Murray, J. (1909). A handbook of wireless telegraphy: its theory and practice, for the use of electrical engineers, students, and operators. New York: Van Nostrand.
- Twining, H. L. V., & Dubilier, W. (1909). Wireless telegraphy and high frequency electricity; a manual containing detailed information for the construction of transformers, wireless telegraph and high frequency apparatus, with chapters on their theory and operation. Los Angeles, Cal: The author.
- The New Physics and Its Evolution. Chapter VII : A Chapter in the History of Science: Wireless telegraphy by Lucien Poincaré, eBook #15207, released February 28, 2005. [originally, published: New York, D. Appleton and Company. 1909].
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External links
Online resources- John Joseph Fahie, A History of Wireless Telegraphy, 1838-1899: including some bare-wire proposals for subaqueous telegraphs, 1899 (first edition).
- John Joseph Fahie, A History of Wireless Telegraphy: including some bare-wire proposals for subaqueous telegraphs, 1901 (second edition).
- John Joseph Fahie, A History of Wireless Telegraphy: including some bare-wire proposals for subaqueous telegraphs, 1901 (second edition, in HTML format).
- Alfred Thomas StoryAlfred Thomas StoryAlfred Thomas Story was an English journalist, poet and author of numerous books. He was born in North Cave, in the county of York, the fourth child in the large family of James Story. His family was an old Durham branch of the Northumbrian Story family. His father, a property-owner and keen...
, The Story of Wireless Telegraphy, 1904 http://www.archive.org/details/storyofwirelesst00storiala - James Bowman Lindsay A short biography on his efforts on electric lamps and telegraphy.
- Sparks Telegraph Key Review
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