A History of the Marconi Company 1874-1965

W. J. Baker

• Publisher: Routledge
• Year: 2013
• ISBN:
  9781134526147
• Edition: 1
• Topic: Betriebswirtschaft
• Subtopic: Business allgemein

This accessible work provides a detailed picture of the history of one of the most important companies in the electronic industry.

PART ONE

1

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The Stage is Set

The employment of electromagnetic waves for purposes of communication is no modern invention; on the contrary, its origins are lost in time. A boy winks; a girl smiles. Communication via the optical electromagnetic frequencies has taken place, although the participants are unlikely to be thinking of the process in those terms. The discovery of means of making fire, the greatest single forward step in human history, put the power of the artificial generation of electromagnetic waves into the hands of primitive man, giving him means to warm himself and cook his food by the use of infra-red frequencies and the facility of communication at night (camp-fires and beacons).

We are not, however, primarily concerned here with the optical and near-optical frequencies – although modern researches have extended the domain of electronics into those regions – but rather with the bands of radiation which lie roughly between the frequencies of 10 kHz and 300 GHz¹ and for which the human body has no direct means of detection.

The history of scientific progress is closely analogous to the history of an individual. We celebrate the birth of a baby, not the miracle of conception, and tend to take the incredibly complex chemistry of the gestation period rather for granted. Similarly, in science; it is the birth of an invention which is remembered, not its conception or the patient development which made the device practicable.

The discovery of a practical means of wireless communication is a typical instance of this. Every schoolboy – in the Western hemisphere at least – associates the name of Marconi with it, whereas the names of those concerned with the gestation period are much less known outside of scientific circles, although without them there could have been no birth.

In tracing the evolution of any given discovery, the problem is to know where to start, and the history of wireless communication provides no exception. Pursuing the human analogy, we can conveniently attribute its conception to Clerk Maxwell, the first quickening to Hertz and the actual birth to Marconi. This is all very well as far as it goes, but it takes no account of the fact that all these owed a great deal to the efforts of others; Maxwell, for instance, took over from Faraday, and Faraday, in turn, inherited much from his predecessors, who likewise had built upon the findings of even earlier workers – and so on (or rather, back) until we find ourselves with the ancient Greeks and Chinese. As with biological evolution, there is a spark of life which has been present from the very beginning, having been transmitted from generation to generation.

This is an oblique way of reminding ourselves that electronics is not a science in its own right, but an off-shoot of electrical engineering. In order, therefore, to put the advent of wireless telegraphy into perspective it is necessary to consider, in the briefest outline, the history of electricity and magnetism. For purposes of a summary it is reasonable to start at the first Elizabethan period, for although both phenomena were known to the ancients, no sensible growth of information about them had occurred until the sixteenth century. By comparison, optics had made much more headway.

It was Dr Gilbert (or Gilberd), physician to Queen Elizabeth I, who gave the initial impetus to scientific interest in electricity and magnetism by publishing his findings. Over the subsequent three centuries the original trickle of experimental work grew into something approaching a stream, with many important discoveries emerging. Devices for generating electric charges were invented and this circumstance originated a need for a means of storing such charges, thereby bringing the Leyden jar into being. The discovery of chemical means whereby electricity could be made available in a steady flow was another great step forward.

The physics of light was also being investigated, with such giants as Newton and, later, Huygens, dominating scientific thought. Physics in general made great strides between the sixteenth and nineteenth centuries and by the beginning of the nineteenth century a great deal had been found out about electricity and to a lesser extent, magnetism, although the interchangeable nature of these had not been discovered. In 1822 Georg Simon Ohm tore another veil from the mystery of electricity by establishing the mathematical relationship between voltage, current and resistance.

Another genius now arose in the person of Michael Faraday, who, building upon previous work, notably by Ampere and Oersted, announced his discovery of the principle of electromagnetic induction. This great step forward, which was made in 1831, opened the door to a host of possibilities, including those of the large-scale generation of alternating and direct currents.

At that time the nature of the force which Faraday had discovered was not understood, and although it was patent that when a loop of wire was rotated between the poles of a magnet a transfer of energy took place across the gap, opinion was divided as to how this was effected. The majority school of thought held that this ‘action at a distance’ could only be accounted for by the presence of some medium of contiguous matter. Faraday himself had other ideas, suggesting that the ‘lines of force’ he had discovered spread themselves out in all directions from a point of electric charge or magnetic pole and that any alteration in the state of these must have its consequences throughout the space they permeated.

But Faraday was no mathematician, and unfortunately his concept needed the backing of mathematical proof before it could be accepted. In 1855, James Clerk Maxwell, already at twenty-three a mathematician of some note, read his first paper on Faraday’s Lines of Force, but while this succeeded in expressing Faraday’s findings mathematically it did not carry matters to the point where the ‘action at a distance’ hypothesis could be positively rejected.

Maxwell was by now deeply engrossed in the problem. He devised a mechanical model to illustrate Faraday’s Law of electromagnetic induction, whereby changes in a magnetic field were stated to produce an electric force; this it did successfully and Maxwell discovered on using it that it suggested that the process was reversible – that is, that changes in the electric force would produce a magnetic field. The realization of this concept of interchangeability led directly to the thought that all changes in electric and magnetic fields cause electromagnetic waves in space.

This model was used in conjunction with Maxwell’s paper of 1862 Physical Lines of Force, in which the forerunners of the Maxwell Equations appear. These were fully developed in his classic treatise of 1865 A Dynamical Theory of the Electromagnetic Field in which the electromagnetic wave theory was mathematically expounded. Experiments conducted by Maxwell gave a rate of propagation of these waves which tallied closely with that of light as determined by Fizeau (it is a curious fact that although Fizeau’s and Maxwell’s calculations agreed to within thirty miles per second the figure they arrived at was subsequently found to be more than 6,000 miles per second in error). But the almost perfect agreement had led Maxwell to state:

... we have strong reason to believe that light itself – including radiant heat and other radiations if any – is an electromagnetic disturbance in the form of waves propagated through their electromagnetic field according to electromagnetic laws.

The seed of Maxwell’s theory fell on rather stony ground because it upset too many preconceived ideas all at once, and because his mathematical presentation was obscure. It took many years to establish a significant following for the Maxwellian theory and in the interim the invisible waves which the master had postulated were discovered by accident. This circumstance took place in 1875 when Professor Elihu Thomson was demonstrating an induction coil at a lecture at the Central High School, Philadelphia, and had connected one terminal of the apparatus to a water-pipe and the other to a piece of metal insulated from earth. Thomson made the fortuitous discovery that tiny sparks were produced when the point of a pencil was brought near to a metal door knob in the lecture hall; it is stated that he pursued this phenomenon to various floors in the building and found the effect present in a room a hundred feet away from the induction coil.

The discovery was not widely publicized and Professor Thomson seems not to have carried out further investigation; neither did he connect it with Maxwell’s work. The field of practical discovery thereafter lay dormant until 1883 when Fitzgerald, a new convert to the Maxwell school of thought, suggested that it might be possible to generate invisible waves by employing the discharge of a Leyden jar, which was already known to be oscillatory in character.

What would today be known as the breakthrough came in 1888 when Heinrich Hertz announced in Weidemann’s Annalen der Physik that he had succeeded in producing what he described as an ‘outspreading of electric force’ (it was Lord Kelvin, in a translation of Hertz’ work, who coined the expression ‘aether waves’). It is significant that Hertz had been a pupil of Von Helmholtz who was one of the first in Europe to accept Maxwell’s theory; without doubt Von Helmholtz’ influence was responsible for Hertz’ pursuance of the matter.

The Hertzian apparatus used was beautifully simple. The transmitter consisted of a pair of flat metal plates, each of which was joined to a short metal rod terminating at the far end in a metal ball. These two units were supported end-on, with the metal knobs innermost and nearly touching each other; each unit was connected to one output terminal of an induction coil which formed a high voltage supply. This assembly formed, in essence, a capacitor or Leyden jar around which a strong electric displacement was created as the induction coil charged it.

Figure 1.1 Hertz Transmitter

At a critical potential the capacitor broke down, discharging itself in the form of a spark across the air dielectric between the two metal balls; this resulted in a sudden disruption of the electric field, which in turn created a magnetic flux in space. The persistence of this flux produced an electric displacement in the reverse direction and so an oscillatory process was initiated. Assuming that this oscillation was started sufficiently suddenly, some of the energy was radiated by the Hertzian dipole in the form of a damped wave. With the induction coil permanently switched on, a series or train of damped waves was radiated.

The receiver, or resonator, consisted of a metal circlet broken at one point, with the two ends terminating in small metal balls just out of contact with one another. The radiation was detected visually by the presence of tiny sparks jumping the gap.

At this point the question may be raised as to why Hertz and not Thomson is regarded as the discoverer of aether waves. The answer to this must surely be that, whereas Professor Thomson’s discovery was accidental, and incidental to his immediate purpose, the work of Professor Hertz was a deliberate series of experiments designed to test Maxwell’s theory. Just how completely Hertz achieved this is shown by the fact that he not only succeeded in generating the waves, but also showed that they obeyed the optical laws governing reflection, refraction and interference, and furthermore that they travelled at the same velocity as light.

Figure 1.2 Hertz Resonator or Receiver

In view of the intense interest which the discovery aroused in scientific circles it is curious that no mention of the possibility of using these waves as conveyors of intelligence seems to have been made until 1892, when Sir William Crookes suggested that they might conceivably be employed for this purpose; at the same time he foreshadowed the use of some form of tuning in order to avoid interference between two transmissions.

The years which intervened between Hertz’ discovery and the practical utilization of his waves were nevertheless not wasted, for valuable – indeed essential – pieces of apparatus were evolved during this time. Before discussing these, however, it might be appropriate first to mention various other means of communicating through space which were already in existence, and which from time to time (usually in the daily Press) still give rise to a statement that this inventor or that was the ‘Father of Wireless’.

The methods which were being investigated fall into one or other of the following categories:

1. The conduction of electric currents through water or moist earth. Many names are associated with this approach, notably Morse, Lindsay, Trowbridge, Preece, Rathenau, Stecker, Wilkins and Melhuish.
2. Electromagnetic induction between parallel conductors, either in the form of complete circuits or by using the earth return method. Trowbridge, Preece and Lodge were among the investigators. Preece, by combining methods (1) and (2), evolved a practical system for the British Post Office, although this was limited in its range and scope.
3. Electrostatic induction between separated conductors. This method was pioneered with some success by Edison, Gilliland, Phelps, W. Smith and others, chiefly as a means of communicating with railway trains in motion.

In the assessment of claims made on behalf of individual workers in these fields we have to consider carefully the meaning of words. If the word ‘wireless’ is taken to mean ‘signalling through space’ then it must be conceded that those experimenters in fields (2) and (3) above undoubtedly achieved communication between two points and therefore would have prior claims. But the term ‘wireless’ means more than this. It relates to a method of signalling through space by a particular means – that of causing electromagnetic waves to radiate from an antenna system: broadly speaking, one of the fundamental differences between the conduction and induction methods and ‘wireless’ lies in the frequencies employed, the former using speech frequencies of only a few kHz and the latter much higher frequencies, with about 16 kHz as the minimum.

From the practical point of view the conduction or induction methods are limited in usefulness by their very short range. The G.P.O. system mentioned above, which was easily the most successful within the ‘induction’ category, needed the installation of two parallel conductors roughly equal in length to the distance to be bridged; as a consequence, on an overland circuit it would be cheaper to string one conductor between the two points to be bridged, using an earth return. The only place where the induction system might be used with advantage would be for communication with an off-shore island; indeed, the G.P.O. used it in this capacity.

Not all the alleged inventions of signalling without wires which were devised in the nineteenth century will bear critical scrutiny. Marconi himself, in an unpublished document in the Company’s archives, mentions, in passing, two of these. One was a belief of the Rosicrucians, that if little pieces of flesh were transplanted from one person to another, each piece being tattooed with a letter of the alphabet, it was only necessary to prick the graft corresponding to a particular letter and its original owner would feel the pain in the very spot from which the skin had been taken.

Even more bizarre, about 1850 a Monsieur Benoit of Paris was alleged to have talked to a compatriot, M. Bial Cretien, in America, by means of snails. It seems that two snails, once placed in contact, are ever after in sympathetic communion; the basis of the invention was similar metal bowls in Paris and New York, in which snails were placed in contact with letters of the alphabet. When a snail was touched in Paris its sympathetic counterpart in New York would put out its horns and in this way messages could be exchanged. The medium of transmission was stated to be ‘escargotic fluid’ which was described as ‘galvano-terrestrial-magnetic-animal and adamic force’.

Far more feasible was the claim made in 1872 by Mahlon Loomis, an American dentist, who took out a patent for ‘establishing an electrical current for telegraphic or other purposes without the aid of wires, batteries or cables’. Loomis elevated two kites, using wires in place of string, on two adjacent mountain tops and is stated to have signalled from one to the other by discharging the static electricity collected by the ‘transmitter’ cable. Although this scheme is clearly impractical from the commercial point of view, it would, at least, seem to make use of a sudden discharge to create electromagnetic waves and to indicate that Loomis was the first to use elevated antennas for signalling purposes.

Another candidate with a claim to have generated electromagnet...