A Brief Historical Review
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 (bio) (photo) and his associates devised a different sort of wireless telegraph, which bore a closer resemblance to the radio of to-day. 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 (bio) (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, (bio) (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, (bio) (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, (bio) (bio#2 w/photo) of the University of Pittsburgh.
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-requency 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 (bio) (photo-1940) had added a third electrode, called the “grid”, in 1906, and E. H. Armstrong (bio) (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 l9l2 vacuum tubes could be used to transmit for only a few miles, whereas now they are produced in units rivalling 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 I902 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 l902 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.
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, l899, 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 Co1umbia 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, 19O2, 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.
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.
Edited for Hypertext by John Dilks Link back to the NJ Antique Radio Club HomePage