There really is no simple answer to the question who invented the radio, as many people contributed to its inception and development. For those who are eager to know the details, we offer a contemporaneous inside story, written by John Vincent Lawless Hogan in 1922-1923 as the first chapter of his book The outline of radio. Hogan certainly knew what he was talking about, as he himself discovered the "rectifier heterodyne" — multiplying the sensitiveness of radio receivers literally more than a hundred times — and designed and patented a very succesful single-dial tuning system for radio receivers. This reprint was edited for the internet by John H. Dilks.
Scientists in many countries have helped in the development of radio signaling; but neither the United States, Great Britain, France, Italy, nor Germany need be unduly modest over the contributions of its workers. A chronological record of the art's advances will skip from one country to another; a bit suggested by one man here has been adopted and improved upon by another investigator there, and the combination of ideas has marked an additional step forward. Radio as we know it to-day is no single invention or discovery; modern instruments utilize the novelties devised by a host of engineers and physicists whose work extends over the past seventy years or more.
In outlining the growth of radio, one hardly knows where best to begin. It does not seem worth while to go back of the first electrical methods of signaling. We have all heard of or seen (or perhaps experimented with) many of the crude schemes which some writers have called "wireless telegraphy". Waving lanterns at night or flags by day; blowing whistles according to some code dependent upon the number and length of the blasts; striking stones together under the surface of a lake and listening to the sound transmitted through the water; building huge fires visible from one mountain top to another, — all of these ancient plans are, in a sense, wireless telegraphy. That is, they are forms of signaling over substantial distances by the use of arbitrary codes, and they do not use wires connecting the transmitting and receiving points. They are not, however, in the least suggestive of radio, and they do not even involve electrical effects. Certainly they contributed nothing to the growth of radio.
The inception of wireless. Let us, then, begin with the first electrical arrangement for wire-less telegraphy. It was not long before Samuel F.B. Morse transmitted (May 24, 1844) his famous first message, "What hath God wrought!", over the experimental telegraph wire line from Washington to Baltimore — indeed, quite soon after he built his earliest wire telegraph — that he began trying to telegraph without complete wire circuits. In 1842 he succeeded in sending messages across a canal at Washington, using the slight conducting power of the water to carry the electric telegraph current from one side to the other. The same plan was tried out by others in the decade following; but although distances of nearly one mile were covered by the use of large amounts of power, it seems never to have passed beyond the experimental stage.
More than thirty years later, in 1875, Alexander Graham Bell built his first telephone. This surprisingly sensitive instrument could reproduce musical signal sounds from comparatively feeble currents of electricity, and was in many ways far superior to the receivers used by earlier investigators of the telegraph. John Trowbridge, of Harvard University, in 1880 applied the Bell telephone to the study of Morse's scheme of wireless telegraphy by diffused electrical conduction through rivers or moist earth. He found that if he interrupted the signaling current rapidly, so that its variations could produce a musical tone, messages could be transmitted through earth or water much more effectively than Morse had thought possible. In 1882 Bell succeeded in sending messages about a mile and a half to a boat on the Potomac River, using his telephone receiver connected to plates submerged below the water surface.
Developments in England. Contemporaneously with Trowbridge and Bell, Sir William H. Preece applied to wireless signaling his knowledge of "cross talk" between neighboring circuits carrying telephone and telegraph messages by wire. Perhaps his first practical installation was that between Hampshire, England, and the Isle of Wight when in 1882 the submarine cable across The Solent (averaging a little over one mile in width), broke down. Preece got good results in much the same way as did Morse and Bell. Preece also experimented with the magnetic effects between circuits having no interconnection by wire, earth, or water; and with the assistance of A.W. Heaviside succeeded in transmitting both telegraph and telephone messages by wireless in this way as early as 1885. However, by combining the two arrangements and taking advantage of both magnetic induction between the circuits and diffused conduction between their terminals, he was able to increase working distances to more than six miles.
This magnetic induction between completely closed circuits was only one of the actions suggested for, and practically applied to, electric signaling without connecting wires, during these early years. In 1885 Thomas A. Edison [see: biography; photo] and his associates devised a different sort of wireless telegraph, which bore a closer resemblance to the radio of today. Edison's proposal was to support, high above the earth's surface and at some distance from each other, two metallic plates. At the sending station one of these was connected to earth through a coil that would produce a high electrical pressure; the other, at the receiving station, was connected through a Bell telephone to the ground. In operation, the intense electric strains produced in space about the sending plate (by reason of its high voltage) were supposed to extend outward as far as the receiving plate and to produce currents of sufficient strength to give off signal tones from the telephone. A modification of this system, by which the receiving plate was mounted on the roof of a railway car and the telegraph wires beside the tracks were utilized to help out the transmission, was used on the Lehigh Valley Railroad in 1887. It operated satisfactorily, and this was probably the first instance on record of telegraphing to a moving train.
Signaling with electric waves: a new kind of wireless. So much for the several types of electrical signaling, without connecting wires, which preceded radio-telegraphy and radio-telephony. There were other suggestions, notably those of Mahlon Loomis (1872), Professor Amos Dolbear (1886), and Isidor Kitsee (1895); but so far as is known, none of them attained even the degree of practical success achieved by Morse in 1842. However that may be, all these plans dependent upon electrical conduction or induction were utterly eclipsed soon after Guglielmo Marconi's [see: biography; photo] experimental demonstrations of electric-wave telegraphy in 1896 and 1897. This new form of wireless signaling, depending upon radiated electromagnetic waves, showed so much promise and made such rapid development that interest in the earlier types soon vanished. The new wireless art quickly gained an importance so great that it required a characteristic name to distinguish it from the earlier conduction and induction systems. The name given to it is "radio communication". Radio, therefore, is only one part of the subject of wireless electrical signaling. It is, however, by so much the largest and most important part that "radio" has become practically synonymous with "wireless", and sight has largely been lost of the fact that, strictly speaking, radio includes electro-magnetic wave transmission and nothing else.
The work upon which radio is founded. Curiously enough, although radio did not reach practical success until about 1896, its underlying principles had been matters of scientific development for many years before. In 1842, the same year that Morse telegraphed through the canal at Washington, Professor Joseph Henry at Princeton University showed that the magnetic effects of an electric spark could be detected some thirty feet away. In 1867 Professor James Clerk Maxwell [see: biography; photo], of the University of Edinburgh, propounded a radically new conception of electricity and magnetism, outlined theoretically the exact type of electro-magnetic wave that is used in radio to-day, and predicted its behavior. Twelve years later Professor David E. Hughes discovered the sensitiveness of a loose electrical contact, both to sounds and to electrical spark effects which he suspected might be waves. He found it possible to indicate the passage of electric sparks nearly one third of a mile away. But it was not until 1886 that the existence of veritable electromagnetic waves was demonstrated beyond the possibility of misunderstanding or criticism. In that year, Heinrich Hertz, [see: biography; photo] working at Karlsruhe, Germany, confirmed Maxwell's theory by creating and detecting these electric waves. With the instruments he devised, it was possible to reflect and to focus the new waves. Their similarity to the waves of light and heat was clearly shown.
Hertz's electric-wave generator consisted of a spark gap to which was attached a pair of outwardly extending conductors, corresponding in a miniature way to the aerial and earth wires of a modern radio transmitter. His receiver was a wire ring having a minute opening across which, when electro-magnetic waves arrived, tiny sparks would pass. This wire ring was in some respects like the loop receiver of today; with it Hertz was able not only to indicate the receipt of waves, but also to determine their intensity and direction of travel. Heinrich Hertz, despite the fact that his work was limited to laboratory distances and that he did not suggest the use of his waves for telegraphy, is the pioneer whose experiments laid the foundation for radio as we now know it.
A few years after Hertz's first work with invisible electro-magnetic waves, Elihu Thomson, of Lynn, Massachusetts, proposed (1889) their use for signaling through fogs or even through solid bodies that would shut off light waves. Sir William Crookes in 1892 made a startling prophecy of electric-wave telegraphy and telephony. Meanwhile, Hertz's experiments had been taken up and extended by a number of scientists, chief among whom were Professor Edouard Branly, of Paris; Sir Oliver Lodge, of London; and Professor Augusto Righi, of Bologna, Italy. Branly and Lodge devised numerous forms of "radio conductors", or receivers utilizing some of the phenomena also discovered by Hughes, for the delicate reception of electric waves; Righi invented various types of wave producers and con-firmed and added to Hertz's observations.
The earliest experiments with radio. Guglielmo Marconi, who is justly called the inventor of radio-telegraphy, was a pupil of Righi's. To him came not merely the idea that invisible electric waves could be used for telegraphic signaling, but also the inspiration that led to practical solutions of the many problems involved in producing a set of sending and receiving instruments capable of reasonably reliable operation. As early as 1894 he recognized the defects in the indicators previously used to show the arrival of electric waves. He applied himself to the building of a sensitive and, for those days, dependable device that would receive and record a message in the dots and dashes of the Morse code. Such a receiver was made; and, having come to England, Marconi carried on the famous Salisbury Plain demonstration in 1896. There he telegraphed by radio a distance of nearly two miles. This spectacular performance resulted from the sensitiveness of Marconi's new receiver, but perhaps no less depended upon his idea of connecting one side of his spark gap to the ground and upon his use of comparatively large elevated or aerial conductors at both the sending and the receiving station.
Before the end of the next year (1897), Marconi had sent radio messages to and from ships at sea over distances as great as ten miles, and between land stations at Salisbury and at Bath, 24 miles apart, in England. This was sufficient to settle beyond cavil the economic importance of radio-telegraphy, and to bring to bear upon its puzzles the best scientific minds of Europe and America. The earlier systems of wireless, none of which utilized electric radiation, had never been capable of such results as these.
Later developments. In the quarter-century that has passed since Marconi sent the first messages by radio, the complexion of the art has changed in great measure; yet one has no difficulty in recognizing many of Marconi's fundamentals as they reappear in the instruments now used. The high aerial wires at the transmitter, the ground connection, either direct or through a wire network, as suggested by Lodge in 1898, and the invention of "tuning" (dating from 1900) all persist in the apparatus of to-day.
Marconi's original transmitter was simply an enlarged wave-producer of the sort used by Hertz. Very soon, however, Marconi found that greater distances could be covered by connecting one side of the generating spark gap to an earth wire and the other to a high vertical aerial wire or antenna. Even this form was limited in power; and the next important step seems to have been made by dividing the sending assembly into two parts — a driving circuit and a radiating circuit. Sir Oliver Lodge, in 1897, partially applied to radio the idea of electrical tuning, the principles of which had been stated by Professor M.I. Pupin, of Columbia University, in 1894; but his method was greatly improved upon in 1900 by carefully adjusting the two divisions of the transmitter to work harmoniously together. This advance in powerful and non-interfering transmission appears to have been made independently by Marconi and by Professor R.A. Fessenden, [see: biography] of the University of Pittsburgh.
Overcoming a serious defect. The spark transmitter of 1900, with, of course, practical improvements, is still in quite extensive use. The type has a number of defects, however, which will probably render it obsolete in the not distant future. As first built, it sent out signal energy for less than one one-thousandth of the time during which it was supplied with power. This source of inefficiency led Fessenden, in 1902, to invent the continuous-wave system, and to devise various ways of radiating signal energy continuously instead of in short groups. The principal generator of Fessenden's is the radio-frequency alternator. By 1906 he had built, with the assistance of E.F.W. Alexanderson, [see: biography] such generators in sizes capable of transmitting messages several hundreds of miles. Since then, Alexanderson has produced alternators large enough to work reliably in transoceanic radio service [see: photo].
Listen to the sound of the spark transmitter of 1900 (CW de BO)
The third general type of radio transmitter, in point of time, is the special arc light invented by Valdemar Poulsen of Denmark. This instrument also generates continuous streams of waves, and embodies principles used by Elihu Thomson in 1892 and by William Duddell about 1900 for the production of slower alternating currents. Poulsen, however, seems to have been the first to obtain practical radio waves from an arc generator. The Poulsen arc has been a strong competitor of the radio-frequency alternator, and is now much used for both long and short distance radio-telegraphy.
The latest and most interesting radio generator is the oscillating vacuum tube or incandescent lamp. This device may be traced back to experimental lamps made by Edison in 1884 and to the incandescent-lamp receiver of J.A. Fleming, which Fleming applied to radio reception in 1904; but it did not become a practical transmitting element until after Lee de Forest [see: biography; photo 1940] had added a third electrode, called the "grid", in 1906, and E.H. Armstrong [see: biography; photo] had applied to it a special relay circuit in 1912. Since then, the vacuum tube has made great progress as a transmitter, largely on account of technical improvements made by H.D. Arnold, Irving Langmuir, W.D. Coolidge, and others. In 1912 vacuum tubes could be used to transmit for only a few miles, whereas now they are produced in units rivaling the huge alternators of the trans-Atlantic radio stations.
The improvement of receiving apparatus. Turning to the development of receivers, we find that the delicate instrument used by Marconi in 1896 was the subject of much investigation and that many other forms of "loose contacts" were invented up to 1900 or thereabout. The erratic action of these devices, however, forced the investigators into other channels. By 1902 Marconi had produced a magnetic detector that was entirely dependable but not exceptionally sensitive. In the same year Fessenden patented a uniformly operating thermal receiver of about the same sensitiveness. In 1903 Fessenden brought forward his liquid receiver, which had such great responsiveness and stability that it was generally adopted in practical radio and became the U.S. Navy's standard of sensitiveness. Fleming's incandescent-lamp receiver came out in 1904, but in its original form could not compete with the simple liquid detector. Of the "crystal" detectors, now so common, one of the first to attain practical use was the electric-furnace product, carborundum, which General Henry H.C. Dunwoody, of the U.S. Army, applied to radio in 1906. Contemporaneously, G.W. Pickard found that silicon and other substances might be utilized in the same way, and lead ore (galena) and iron pyrites were also much used. The best of these so-called crystal receivers were nearly equivalent in sensitiveness to the earlier liquid type, and because of their ease of manipulation they almost entirely superseded the older devices.
In 1906 and 1907 de Forest introduced the grid audion, which proved to be a substantially improved form of Fleming's incandescent-lamp receiver. This vacuum-tube detector showed surprisingly great sensitiveness from the very first; its earlier forms were unstable, however, and it was not accepted practically until about 1912. With the structural improvements that followed — the addition of the Armstrong feed-back circuit, and the discovery (about 1913) that the same three-electrode bulb could be used as a delicate but powerful magnifier of signal strength — the vacuum tube has now replaced all other receivers at stations where extreme sensitiveness is desired. The modern forms do not closely resemble the designs of 1906; and in special types of tube, such as those named the "magnetron" and the "dynatron", there is also a departure from the earlier operating principles. All of these tubes are, however, incandescent-lamp detectors or amplifiers.
Improvements at the receiving end of radio were by no means confined to the sensitive wave-detecting elements. The Pupin-Lodge-Fessenden-Marconi tuning improvements were applied to receiving systems as well as to transmitters. There was also an effort to replace the ink recorder used in Marconi's first work. Lodge in 1897 adopted the siphon recorder, which Lord Kelvin had devised for cable working; while other investigators (and notably those in the United States) put the Bell telephone into use as a signal indicator as early as 1899. In 1902 Fessenden showed how the ordinary detector could be replaced by a special telephone receiver operated by two simultaneously transmitted streams of continuous waves. Not long thereafter he invented the strikingly novel and ingenious "heterodyne" receiver which, with later improvements, is well-nigh universally used in modern radio-telegraphy.
Fessenden's 430' Tower at Brant Rock
Sending speech by radio. The technical developments of radio outlined in the preceding pages have been discussed mainly from the viewpoint of Morse signaling, or "dot-and-dash" telegraphy, although in connection with induction and conduction wireless the possibility of telephony has been indicated. In the growth of radio it appears that voice transmission was not proposed until Professor Fessenden in 1902 suggested that his continuous-wave method of transmission was suitable for radio-telephony. There seems to be some evidence that Fessenden made practical trials of speaking radio even before this date. John Stone Stone, of Boston, has stated that, using a species of arc-lamp generator, he transmitted speech by electro-magnetic waves early in the decade dating from 1900. It is well known, however, that in 1906 Fessenden gave numerous practical demonstrations of radio-telephony between his experimental stations at Brant Pock and Plymouth, Massachusetts, and that in 1907 he increased his range from this distance of about twelve miles to such an extent that Brant Rock was able to communicate with New York, nearly two hundred miles away, and Washington, about five hundred miles. In these tests it was shown that speech carried to the radio station over a wire line could automatically be relayed to the radio and sent broadcast on the wings of the electro-magnetic waves. At the receiving end, Fessenden demonstrated the feasibility of transferring speech, arriving by radio, to telephone wires and thus carrying it to a home or office remote from the wireless installation.
Look at the photo below for Fessenden's Brant Rock radio-telephone installation as used in the first practical experiments in 1906. Note the alternator, the transmitters, the glass-covered relay, and the phonograph. This pioneer radio-frequency alternator was built by Fessenden and Alexanderson in 1906, and generated about one kilowatt of power at 50,000 cycles per second. (Click on the picture for a closer look at Fessenden's speaker, relay, and detector.)
From 1907 to 1912 or thereabout, radio-telephony developed slowly. The Poulsen arc lamp was used to some extent as a power source, but proved an unsatisfactory substitute for the generators used by Fessenden. On the other hand, the radio alternators were expensive and bulky, and had definite practical limitations of power and wave length. Further, and regardless of whether arc or generator were used, the voice-controlling instruments were not highly refined. Thus it was that when the modified incandescent lamp was found to be a reliable wave-producer and power-magnifier, progress in radio-telephony came with rapid strides.
By 1915, the engineers of the American Telephone and Telegraph Company had succeeded in talking by radio from the huge naval station at Arlington, Virginia, to Paris, and in the opposite direction, to Honolulu. This great experimental feat was accomplished by using vacuum tubes as oscillators and voice-magnifiers. The power of the transmitter was utterly inadequate to signal over so huge a distance except under the most favorable conditions, but the work indicated possibilities which nothing but the demonstration would have made credible. Since 1915, the trend in radio-telephony has been toward dependable operation over shorter distances. The greatest single advances are probably the control systems devised by R.A. Heising and E.F.W. Alexanderson.
The radio-telephone transmitters used at Arlington Virginia for the long-distance experiments of 1915
The field of practical operation. To conclude this necessarily rather sketchy historical review, a glance at progress in the application of radio to operations, rather than its scientific growth, may be interesting. After Marconi's demonstrations in 1897, a number of commercial installations were made on both ship and shore. The first instance of reporting a marine accident by radio was in Mach, 1899, when the S.S. R.F. Matthews collided with the East Goodwin light vessel. In the same year British naval vessels communicated over distances as great as 85 miles, and the international yacht races between the Shamrock and the Columbia in America, were reported to the press by wireless. In 1901 radio stations on the Isle of Wight and the Lizard, 196 miles apart, intercommunicated successfully; and construction of the Poldhu (England) and Newfoundland stations for trans-Atlantic signaling was well under way. December, 1901, marked the first transoceanic radio signaling, for then Marconi succeeded in intercepting repetitions of the single letter "S", in the Morse code, sent from Poldhu to an experimental receiver at St. John's, Newfoundland The next year, 1902, Poldhu's signals were heard aboard the S.S. Philadelphia over more than 2,000 miles, complete messages having been received up to more than 1,500 miles.
In January, 1903, a trans-Atlantic radio message was sent from President Roosevelt to King Edward VII by way of the stations at Cape Cod, Massachusetts, and Poldhu, England; but it is not generally known whether this message was relayed by ships on the Atlantic or whether it was received directly from Cape Cod in complete form. A station even larger than that at Poldhu was begun in 1905, at Clifden, Ireland, and in 1907 this plant and a twin station at Glace Bay, Nova Scotia, were opened for a limited commercial trans-Atlantic radio service. January 23, 1909, was the date of the collision between the steamships Florida and Republic, which was reported to neighboring ships by radio in time to save all the passengers and crew of the Republic before she sank. In 1910 messages from the powerful Clifden station were heard aboard the S.S. Principessa Mafalda over more than 6,500 miles.
On the morning of April 15, 1912, over seven hundred passengers of the S.S. Titanic were rescued through the aid of radio when the vessel was sunk by striking an iceberg. During the next year, radio messages were successfully sent from and received on moving trains of the De!aware, Lackawanna and Western Railroad. In 1914 commercial trans-Pacific radio-telegraphy was inaugurated between San Francisco and Honolulu, and direct radio communication between the United States and Germany was made available over the Tuckerton-Hannover and Sayville-Nauen channels. In 1915 the United States Government took over the operation of the Sayville and Tuckerton stations to prevent their unneutral use. Commercial service between the United States and Japan was begun in 1916, but development of American-European commercial communication was prevented by the World War until after the armistice was signed on November 11, 1918. Wartime applications of radio on aircraft, in long-distance service, for location of ships' positions, etc., were rapidly adapted to peaceful public uses in 1919 and 1920; the trans-Atlantic fliers in the "NC-4" succeeded (1919) in sending messages 1,800 miles from the plane while in the air. During 1920 and 1921 radio services with Europe were recommenced from the newly equipped, powerful stations along the Atlantic coast of the United States, and 1922 saw the opening and commercial use of the largest plant in the world, located at Port Jefferson, Long Island. In the past few years the ship-and-shore services of radio have reached a new degree of perfection. It is now uncommon for a well-equipped vessel to be out of communication with land at any point of the trans-Atlantic voyage.
Broadcast transmitter at "Old WJZ", Newark, NJ. The first short-wave radio-telephone transmitter to be heard across the Atlantic
Radio broadcasting. Last, but by no means least, the years 1921-1923 brought the commencement and organization of broadcast radiotelephone services, which send out, for whoever desires to listen, scheduled programs of music, lectures, news bulletins, and other recreational and informative material. More than five hundred of these broadcasting stations are in regular operation throughout the United States. The number of listeners is estimated at well over two million. This broadcasting of spoken words and of music is by far the most popular application of radio. It began in November, 1920, by the transmission of election returns from the Westinghouse station [KDKA] [see: Frank Conrad, biography] at Pittsburgh, Pennsylvania, and has spread not merely over the United States but to other nations in a way which proves that the service meets a true human need. Broadcast radio-telephony may not yet have the economic value of the transoceanic or marine radio-telegraph; nevertheless, it has aroused a great general interest in radio, and, as its character and scope improve, it is becoming more and more strongly knit into our ways of living [see: KDKA's original broadcast transmitter, 1922].
A historical introduction is certainly no place for prophecy or speculation. Radio is here and is doing valuable work. We now have glanced at a somewhat broad outline of what radio is and the way in which it has reached its present estate. Let us next find out how radio operates and what the principles are upon which it depends.
"For telephony Fessenden's first attempts to transmit voice employed a spark transmitter operating at something like 10,000 sparks/second. To 'modulate' his transmitter he inserted a carbon microphone in series with the antenna lead ... He experienced great difficulty in achieving intelligible sound. ... let us hear how this telephony transmission employing spark might have sounded like.
On the 23 December 1900, Fessenden, after many unsuccessful tries, transmitted words without wires. The speech you hear is the voice of the author, using the transmitter as described above (the best transmission out of several recorded), but the words are those used by Fessenden the inventor. Listen to Fessenden saying [simulated]:
"Hello test, one, two, three, four. If it's snowing where you are, Mr. Thiessen. If it is, telegraph back and let me know."
Mr Thiessen telegraphed back immediately. It was indeed snowing where he was. After all Mr Thiessen and Professor Fessenden were only one mile apart. But not withstanding, the short distance, and the poor quality of the transmission, this date heralded the beginning of radio telephony."
Quoted from The sounds of a spark transmitter. Telegraphy and telephony by John S. Belrose, Radio Sciences Communications Research Centre Ottawa, ON K2H, 8S2 Canada.
Edited for hypertext by John H. Dilks at firstname.lastname@example.org [see also the New Jersey Antique Radio Club HomePage]. Hogan's book is exactly as written, but has been enhanced with links to additional information such as: links to another web site with a written biography (bio); links to a photo located at another web site (photo); and underlined text: links to additional information about the underlined text and the long footnote above. If you've read the first chapter of The outline of radio on this web page, you might want to find out more about the author: John V.L. Hogan. Hogan was deeply involved with radio when he wrote his book in 1922-23. I encourage you to read his biography.