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Wireless telegraphic communication
Nobel Lecture, December 11,
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Foundation transcript in a PDF version
The discoveries connected with the propagation of electric
waves over long distances and the practical applications of telegraphy through
space, which have gained for me the high honour of sharing the Nobel Prize for
Physics, have been to a great extent the results of one another.
The application of electric waves to the purposes of wireless telegraphic
communication between distant parts of the earth, and the experiments which I
have been fortunate enough to be able to carry out on a larger scale than is
attainable in ordinary laboratories, have made it possible to investigate
phenomena and note results often novel and unexpected. In my opinion many facts connected with the transmission of electric
waves over great distances still await a satisfactory explanation, and I hope
to be able in this lecture to refer to some observations, which appear to
require the attention of physicists.
In sketching the history of my association with radiotelegraphy, I might
mention that I never studied physics or electrotechnics in the regular manner,
although as a boy I was deeply interested in those subjects.
I did, however, attend one course of lectures on physics under the late
Professor Rosa at Livorno, and I was, I think I might say, fairly well
acquainted with the publications of that time dealing with scientific subjects
including the works of Hertz, Branly, and Righi.
At my home near Bologna, in Italy, I commenced early in 1895 to carry out tests
and experiments with the object of determining whether it would be possible by
means of Hertzian waves to transmit to a distance telegraphic signs and symbols
without the aid of connecting wires.
After a few preliminary experiments with Hertzian waves I became very soon
convinced, that if these waves or similar waves could be reliably transmitted
and received over considerable distances a new system of communication would
become available possessing enormous advantages over flashlights and optical
methods, which are so much dependent for their success on the clearness of the
My first tests were carried out with an ordinary Hertz oscillator and a Branly
coherer as detector, but I soon found out that the Branly coherer was far too
erratic and unreliable for practical work.
After some experiments I found that a coherer constructed as shown in Fig. 1,
and consisting of nickel and silver filings placed in a small gap between two
silver plugs in a tube, was remarkably sensitive and reliable. This improvement
together with the inclusion of the coherer in a circuit tuned to the wavelength
of the transmitted radiation, allowed me to gradually extend up to about a mile
the distance at which I could affect the receiver.
Another, now well-known, arrangement which I adopted was to
place the coherer in a circuit containing a voltaic cell and a sensitive
telegraph relay actuating another circuit, which worked a tapper or trembler
and a recording instrument. By means of a Morse telegraphic key placed in one
of the circuits of the oscillator or transmitter it was possible to emit long
or short successions of electric waves, which would affect the receiver at a
distance and accurately reproduce the telegraphic signs transmitted through
space by the oscillator.
With such apparatus I was able to telegraph up to a distance of about half a
Some further improvements were obtained by using reflectors with both the
transmitters and receivers, the transmitter being in this case a Righi
This arrangement made it possible to send signals in one definite direction,
but was inoperative if hills or any large obstacle happened to intervene
between the transmitter and receiver.
In August 1895 I discovered a new arrangement which not only greatly increased
the distance over which I could communicate, but also seemed to make the
transmission independent from the effects of intervening obstacles.
This arrangement (Figs. 2 and 3) consisted in connecting one terminal of the
Hertzian oscillator, or spark producer, to earth and the other terminal to a
wire or capacity area placed at a height above the ground, and in also
connecting at the receiving end one terminal of the coherer to earth and the
other to an elevated conductor.
I then began to examine the relation between the distance at
which the transmitter could affect the receiver and the elevation of the
capacity areas above the earth, and I very soon definitely ascertained that the
higher the wires or capacity areas, the greater the distance over which it was
possible to telegraph.
Thus I found that when using cubes of tin of about 30 cm side as elevated
conductors or capacities, placed at the top of poles 2 meters high, I could
receive signals at 30 meters distance, and when placed on poles 4 meters high,
at 100 meters, and at 8 meters high at 400 meters. With larger cubes 100 cm
side, fixed at a height of 8 meters, signals could be transmitted 2,400 meters
These experiments were continued in England, where in September 1896 a distance
of 1 3/4 miles was obtained in tests carried out for the British Government at
Salisbury. The distance of communication was extended to 4 miles in March 1897,
and in May of the same year to 9 miles. Tape messages obtained during these
tests, signed by the British Government Officers who were present, are
In all these experiments a very small amount of electrical power was used, the
high tension current being produced by an ordinary Rhumkorff coil.
The results obtained attracted a good deal of public attention at the time,
such distances of communication being considered remarkable.
As I have explained, the main feature in my system consisted in the use of
elevated capacity areas or antennae attached to one pole of the high frequency
oscillators and receivers, the other pole of which was earthed.
The practical value of this innovation was not understood by many
physicists3 for quite a considerable period, and the results which I
obtained were by many erroneously considered simply due to efficiency in
details of construction of the receiver, and to the employment of a large
amount of energy.
Others did not overlook the fact that a radical change had been introduced by
making these elevated capacities and the earth form part of the high frequency
oscillators and receivers.
Prof. Ascoli of Rome gave a very interesting theory of the mode of operation of
my transmitters and receivers in the Elettricista (Rome) issue of
August 1897, in which he correctly attributed the results obtained to the use
of elevated wires or antennae.
Prof. A. Slaby of Charlottenburg, after witnessing my tests in England in 1897,
came to somewhat similar conclusions.4
Many technical writers have stated that an elevated capacity at the top of the
vertical wire is unnecessary.
This is true if the length or height of the wire is made sufficiently great,
but as this height may be much smaller for a given distance if a capacity area
is used, it is more economical to use such capacities, which now usually
consist of a number of wires spreading out from the top of the vertical
The necessity or utility of the earth connection has been
sometimes questioned, but in my opinion no practical system of wireless
telegraphy exists where the instruments are not connected to earth.
By "connected to earth" I do not necessarily mean an ordinary metallic
connection as used for ordinary wire telegraphs. The earth wire may have a condenser in series
with it (Fig. 4C) , (Although,
Guglielmo Marconi had understood the importance of the earth grounding
in the radioelectric systems and the possibility to have a capacitive coupling
to the earth through a capacitive reactance, he had not realized the importance
of a direct capacitive coupling to the earth as a means for tapping
into the Earth for grounding. See: Errante's capacitive earth grounding
system ) or it may be connected to what is
really equivalent, a capacity area placed close to the surface of the ground
It is now perfectly well known that a condenser, if large enough, does not
prevent the passage of high frequency oscillations, and therefore in these
cases the earth is for all practical purposes connected to the antennae.
After numerous tests and demonstrations in Italy and England
over distances varying up to 40 miles, communication was established for the
first time across the English Channel between England and France5 in
March 1899 (Fig. 5).
From the beginning of 1898 I had practically abandoned the
system of connection shown in Fig. 2, and instead of joining the coherer or
detector directly to the aerial and earth, I connected it between the ends of
the secondary of a suitable oscillation transformer containing a condenser and
tuned to the period of the electrical waves received. The primary of this
oscillation transformer was connected to the elevated wire and to earth (See
This arrangement allowed of a certain degree of syntony, as
by varying the period of oscillation of the transmitting antennae, it was
possible to send messages to a tuned receiver without interfering with others
As is now well known, a transmitter consisting of a vertical
wire discharging through a spark gap is not a very persistent oscillator, the
radiation it produces being considerably damped. Its electrical capacity is
comparatively so small and its capability of radiating energy so large, that
the oscillations decrease or die off with rapidity. In this case receivers or
resonators of a considerably different period or pitch are likely to be
affected by it.
Early in 1899 I was able to improve the resonance effects obtainable by
increasing the capacity of the elevated wires by placing adjacently to them
earthed conductors, and inserting in series with the aerials suitable
By these means the energy-storing capacity of the aerial was increased, whilst
its capability to radiate was decreased, with the result that the energy set in
motion by the discharge formed a train or succession of feebly damped
A modification of this arrangement, by which excellent results were obtained,
is shown in Fig. 7.
In 1900 I constructed and patented a complete system of
transmitters and receivers8 which consisted of the usual kind of
elevated capacity area and earth connection, but these were inductively coupled
to an oscillation circuit containing a condenser, an inductance, and a spark
gap or detector, the conditions which I found essential for efficiency being
that the periods of electrical oscillation of the elevated wire or conductor
should be in tune or resonance with that of the condenser circuit, and that the
two circuits of the receiver should be in electrical resonance with those of
the transmitter (Fig. 8).
The circuits consisting of the oscillating circuit and the
radiating circuit were more or less closely "coupled" by varying the distance
By the adjustment of the inductance inserted in the elevated
conductor and by the variation of capacity of the condenser circuit, the two
circuits were brought into resonance, a condition which, as I have said, I
found essential in order to obtain efficient radiation.
Part of my work regarding the utilization of condenser circuits in association
with the radiating antennae was carried out simultaneously to that of Prof.
Braun, without, however, either of us knowing at the time anything of the
contemporary work of the other.
A syntonic receiver has already been shown in Fig. 6, and consists of a
vertical conductor or aerial connected to earth through the primary of an
oscillation transformer, the secondary circuit of which included a condenser
and a detector, it being necessary that the circuit containing the aerial and
the circuit containing the detector should be in electrical resonance with each
other, and also in tune with the periodicity of the electric waves transmitted
from the sending station.
In this manner it was possible to utilize electric waves of low decrement and
cause the receiver to integrate the effect of comparatively feeble but properly
timed electrical oscillations in the same way as in acoustics two tuning forks
can be made to affect each other at short distances if tuned to the same period
It is also possible to couple to one sending conductor several differently
tuned transmitters and to a receiving wire a number of corresponding receivers,
as is shown in Figs. 9 and 10, each individual receiver responding only to the
radiations of the transmitter with which it is in resonance.9
At the time (twelve years ago) when communication was first
established by means of radiotelegraphy between England and France, much
discussion and speculation took place as to whether or not wireless telegraphy
would be practicable for much longer distances than those then covered, and a
somewhat general opinion prevailed that the curvature of the Earth would be an
insurmountable obstacle to long distance transmission, in the same way as it
was, and is, an obstacle to signalling over considerable distances by means of
Difficulties were also anticipated as to the possibility of being able to
control the large amount of energy which it appeared would be necessary to
cover long distances.
What often happens in pioneer work repeated itself in the case of
radiotelegraphy, the anticipated obstacles or difficulties were either purely
imaginary or else easily surmountable, but in their place unexpected barriers
manifested themselves, and recent work has been mainly directed to the solution
of problems presented by difficulties which were certainly neither expected nor
anticipated when long distances were first attempted.
With regard to the presumed obstacle of the curvature of the Earth, I am of
opinion that those who anticipated difficulties in consequence of the shape of
our planet had not taken sufficient account of the particular effect of the
earth connection to both transmitter and receiver, which earth connection
introduced effects of conduction which were generally at that time
Physicists seemed to consider for a long time that wireless telegraphy was
solely dependent on the effects of free Hertzian radiation through space, and
it was years before the probable effect of the conductivity of the Earth
between the stations was satisfactorily considered or discussed.
Lord Rayleigh, in referring to transatlantic telegraphy, stated in May 1903 :
"The remarkable success of Marconi in signalling across the Atlantic suggests a
more decided bending or diffraction of the waves round the perturberant Earth
than had been expected, and it imparts a great interest to the theoretical
Prof. J. A. Fleming, in his book on The Principles of
Electric Wave Telegraphy11,gives diagrams showing what is now
believed to be the diagrammatic representation of the detachment of semi-loops
of electric strain from a simple vertical wire (Fig. 11). As will be seen,
these waves do not propagate in the same manner as free radiation from a
classical Hertzian oscillator, but glide along the surface of the Earth.
Prof. Fleming further states in the above quoted work:
"The view we here take is that the ends of the semi-loops of electric
force, which terminate perpendicularly on the Earth, cannot move along unless
there are movements of electrons in the Earth corresponding to the wave-motions
above it. From the point of view of the electronic theory of electricity, every
line of electric force in the ether must be either a closed line or its ends
must terminate on electrons of opposite sign. If the end of a line of strain
abuts on the Earth and moves, there must be atom-to-atom exchange of electrons,
or movements of electrons in it. We have many reasons for concluding that the
substances we call conductors are those in which free movements of electrons
can take place. Hence the movements of the semi-loops of electric force
outwards from an earthed oscillator or Marconi aerial is hindered by bad
conductivity on the surface of the Earth and facilitated over the surface of a
fairly good electrolyte, such as sea-water."
Prof. Zenneck12 has carefully examined the effect of earthed
transmitting and receiving aerials, and has endeavoured to show mathematically
that when the lines of electrical force, constituting a wave front, pass along
a surface of low specific inductive capacity, such as the Earth, they become
inclined forward, their lower ends being retarded by the resistance of the
conductor to which they are attached.
It therefore seems well established that wireless telegraphy, as practised at
the present day, is dependent for its operation over long distances on the
conductivity of the Earth, and that the difference in conductivity between the
surface of the sea and land is sufficient to explain the increased distance
obtainable with the same amount of energy in communicating over sea as compared
to over land.
I carried out some tests between a shore station and a ship at Poole, in
England, in 1902, for the purpose of obtaining some data on this point, and I
noticed that at equal distances a perceptible diminution in the energy of the
received waves always occurred when the ship was in such a position as to allow
a low spit of sand about 1 kilometer broad to intervene between it and the land
I therefore believe that there was some foundation for the statement so often
criticized which I made in my first English Patent of June 2, 1896 to the
effect that when transmitting through the earth or water I connected one end of
the transmitter and one end of the receiver to earth.
In January 1901 some successful experiments13 were carried out
between two points on the South Coast of England 186 miles apart, i.e. St.
Catherines' Point (Isle of Wight) and The Lizard in Cornwall (Fig. 12).
The total height of these stations above sea level did not
exceed 100 meters, whereas to clear the curvature of the Earth a height of more
than 1,600 meters at each end would have been necessary.
The results obtained from these tests, which at the time constituted a record
distance, seemed to indicate that electric waves produced in the manner I had
adopted would most probably be able to make their way round the curvature of
the Earth, and that therefore even at great distances, such as those dividing
America from Europe, the factor of the Earths curvature would not constitute an
insurmountable barrier to the extension of telegraphy through space.
The belief that the curvature of the Earth would not stop the propagation of
the waves, and the success obtained by syntonic methods in preventing mutual
interference, led me in 1900 to decide to attempt the experiment of testing
whether or not it would be possible to detect electric waves over a distance of
4,000 kilometers, which, if successful, would immediately prove the possibility
of telegraphing without wires between Europe and America.
The experiment was in my opinion of great importance from a
scientific point of view, and I was convinced that the discovery of the
possibility to transmit electric waves across the Atlantic Ocean, and the exact
knowledge of the real conditions under which telegraphy over such distances
could be carried out, would do much to improve our understanding of the
phenomena connected with wireless transmission.
The transmitter erected at Poldhu, on the coast of Cornwall, was similar in
principle to the one I have already referred to, but on a very much larger
scale than anything previously attempted.14
The power of the generating plant was about 25 kilowatts.
Numerous difficulties were encountered in producing and controlling for the
first time electrical oscillations of such power. In much of the work I
obtained valuable assistance from Prof. J. A. Fleming, Mr. R. N. Vyvyan, and
Mr. W. S. Entwistle.
My previous tests had convinced me that when endeavouring to extend the
distance of communication, it was not merely sufficient to augment the power of
the electrical energy of the sender, but that it was also necessary to increase
the area or height of the transmitting and receiving elevated conductors.
As it would have been too expensive to employ vertical wires of great height, I
decided to increase their number and capacity, which seemed likely to make
possible the efficient utilization of large amounts of energy.
The arrangement of transmitting antennae which was used at
Poldhu is shown in Fig. 13, and consisted of a fan-like arrangement of wires
supported by an insulated stay between masts only 48 meters high and 60 meters
apart. These wires converged together at the lower end and were connected to
the transmitting apparatus contained in a building.
For the purpose of the test a powerful station had been erected at Cape Cod,
near New York, but the completion of the arrangements at that station were
delayed in consequence of a storm which destroyed the masts and antennae.
I therefore decided to try the experiments by means of a temporary receiving
station erected in Newfoundland, to which country I proceeded with two
assistants about the end of November 1901.
The tests were commenced early in December 1901 and on the 12th of that month
the signals transmitted from England were clearly and distinctly received at
the temporary station at St. Johns in Newfoundland.
Confirmatory tests were carried out in February 1902 between Poldhu and a
receiving station on the S.S. "Philadelphia" of the American Line. On board
this ship readable messages were received by means of a recording instrument up
to a distance of 1,551 miles and test letters as far as 2,099 miles from Poldhu
The tape records obtained on the "Philadelphia" at the various distances were
exceedingly clear and distinct, as can be seen by the specimens exhibited.
These results, although achieved with imperfect apparatus, were sufficient to
convince me and my co-workers that by means of permanent stations and the
employment of sufficient power it would be possible to transmit messages across
the Atlantic Ocean in the same way as they were sent over much shorter
The tests could not be continued in Newfoundland owing to the hostility of a
cable company, which claimed all rights for telegraphy, whether wireless or
otherwise, in that colony.
A result of scientific interest which I first noticed during the tests on S.S.
"Philadelphia" and which is a most important factor in long distance
radiotelegraphy, was the very marked and detrimental effect of daylight on the
propagation of electric waves at great distances, the range by night being
usually more than double that attainable during daytime.15
I do not think that this effect has yet been satisfactorily investigated or
explained. At the time I carried out the tests I was of opinion that it might
be due to the loss of energy at the transmitter, caused by the
dis-electrification of the highly charged transmitting elevated conductor under
the influence of sunlight.
I am now inclined to believe that the absorption of electric
waves during the daytime is due to the electrons propagated into space by the
sun, and that if these are continually falling like a shower upon the earth, in
accordance with the hypothesis of Prof. Arrhenius, then that portion of the
Earths atmosphere which is facing the sun will have in it more electrons than
the part which is not facing the sun, and therefore it may be less transparent
to electric waves.
Sir J. J. Thomson has shown in an interesting paper in the Philosophical
Magazine that if electrons are distributed in a space traversed by
electric waves, these will tend to move the electrons in the direction of the
wave, and will therefore absorb some of the energy of the wave. Hence, as Prof.
Fleming has pointed out in his Cantor Lectures delivered at the Society of
Arts, a medium through which electrons or ions are distributed acts as a
slightly turbid medium to long electric waves.16
Apparently the length of wave and amplitude of the electrical oscillations have
much to do with this interesting phenomenon, long waves and small amplitudes
being subject to the effect of daylight to a much lesser degree than short
waves and large amplitudes.
According to Prof. Fleming17 the daylight effect should be more
marked on long waves, but this has not been my experience. Indeed, in some very
recent experiments in which waves of about 8,000 meters long were used, the
energy received by day was usually greater than at night.
The fact remains, however, that for comparatively short waves, such as are used
for ship communication, clear sunlight and blue skies, though transparent to
light, act as a kind of fog to these waves. Hence the weather conditions
prevailing in England, and perhaps in this country, are usually suitable for
During the year 1902 I carried out some further tests between the station at
Poldhu and a receiving installation erected on the Italian Cruiser "Carlo
Alberto", kindly placed at my disposal by H.M. The King of Italy. (See Fig.
During these experiments the interesting fact was observed
that, even when using waves as short as 1,000 feet, intervening ranges of
mountains, such as the Alps or Pyrenees, did not, during the night time, bring
about any considerable reduction in the distance over which it was possible to
communicate. During daytime, unless much longer waves and more power were used,
intervening mountains greatly reduced the apparent range of the
Messages and press despatches of considerable length were received from Poldhu
at the positions marked on the map, which map is a copy, on a reduced scale, of
the one accompanying the official report of the experiments (Fig. 16).
With the active encouragement and financial assistance of the Canadian
Government, a high power station was constructed at Glace Bay, Nova Scotia, in
order that I should be able to continue my long-distance tests with a view to
establishing radiotelegraphic communication on a commercial basis between
England and America.19
On December 16, 1902 the first official messages were exchanged at night across
the Atlantic, between the stations at Poldhu and Glace Bay (Figs. 17 and 18).
Further tests were shortly afterwards carried out with another long-distance
station at Cape Cod in the United States of America, and under favourable
circumstances it was found possible to transmit messages to Poldhu 3,000 miles
away with an expenditure of electrical energy of only about 10 kilowatts. In
the spring of 1903 the transmission of press messages by radiotelegraphy from
America to Europe was attempted, and for a time the London Times
published, during the latter part of March and the early part of April of that
year, news messages from its New York correspondent sent across the Atlantic
without the aid of cables.
A breakdown in the insulation of the apparatus at Glace Bay made it necessary,
however, to suspend the service and unfortunately further accidents made the
transmission of messages uncertain and unreliable.
As a result of the data and experience gained by these and other tests which I
carried out for the British Government, between England and Gibraltar, I was
able to erect a new station at Clifden in Ireland, and enlarge the one at Glace
Bay in Canada, so as to enable me to initiate, in October 1907, communication
for commercial purposes across the Atlantic between England and Canada.
Although the stations at Clifden and Glace Bay had to be put into operation
before they were altogether complete, nevertheless communication across the
Atlantic by radiotelegraphy never suffered any serious interruption during
nearly two years, until, in consequence of a fire at Glace Bay this autumn, it
has had to be suspended for three or four months.
This suspension has not, however, been altogether an
unmitigated evil, as it has given me the opportunity of installing more
efficient and up-to-date machinery. The arrangements of elevated conductors or
aerials which I have tried20 during my long-distance tests, are shown
in Figs. 19, 20 and 21.
The aerial shown in Fig. 21 consisted of a nearly vertical portion in the
middle, 220 feet high, supported by four towers, and attached at the top to
nearly horizontal wires, 200 in number and each 1,000 feet long, extending
radially all round and supported at a height of 180 feet from the ground by an
inner circle of 8, and an outer circle of 16 masts.
The natural period of oscillation of this aerial system gave a wavelength of
12,000 feet. Experiments were made with this arrangement in 1905 and with a
wavelength of 12,000 feet, signals, although very weak, could be received
across the Atlantic by day as well as by night.
The system of aerial I finally adopted for the long-distance stations in
England and Canada is shown in Fig. 22. This arrangement not only makes it
possible to efficiently radiate and receive waves of any desired length, but it
also tends to confine the main portion of the radiation to a given direction.
The limitation of transmission to one direction is not very sharply defined,
but the results obtained with this type of aerial are nevertheless exceedingly
Many suggestions respecting methods for limiting the direction of radiating
have been made by various workers, notable by Prof. F. Braun, Prof. Artom, and
Messrs. Belhni and Tosi.
In a paper read before the Royal Society of London21 in March 1906 I
showed how it was possible by means of horizontal aerials to confine the
emitted radiations mainly to the direction of their vertical plane, pointing
away from their earthed end. In a similar manner it is possible to locate the bearing or
direction of a sending station.
The transmitting circuits at the long-distance
stations are arranged in accordance with a comparatively recent system for
producing continuous or slightly damped oscillations, which I referred to in a
lecture before the Royal Institution of Great Britain on March 13, 1908.
An insulated metal disc A (see Fig. 23) is caused to rotate at a high rate of
speed by means of an electric motor or steam turbine. Adjacent to this disc,
which I will call the middle disc, are placed two other discs C' and C'' which
may be called polar discs, and which are also revolved. These polar discs have
their peripheries very close to the surface or edges of the middle disc. The
two polar discs are connected by rubbing contacts to the outer ends of two
condensers K, joined in series, and these condensers are also connected through
suitable brushes to the terminals of a generator which should be a high-tension
On the middle disc a suitable brush or rubbing contact is provided and between
this contact and the middle point of the two condensers an oscillating circuit
is inserted, consisting of a condenser E in series with an inductance, which
last is inductively connected with the radiating antennae.
The apparatus works probably in the following manner: The generator charges the
double condenser, making the potential of the discs, say C' positive and C''
negative. The potential, if high enough will cause a discharge to pass across
one of the gaps, say between C' and A. This charges the condenser E through the
inductance F, and starts oscillations in the circuit. The charge of F in
swinging back will jump from A to C'', the potential of which is of opposite
sign to A, the dielectric strength between C' and A having meanwhile been
restored by the rapid motion of the disc, driving away the ionized air.
The condenser E therefore discharges and recharges
alternatively in reverse directions, the same process going on so long as
energy is supplied to the condensers K by the generator H.
It is clear that the discharges between C' and C'' and A are never simultaneous
as otherwise the centre electrode would not be alternatively positive and
The best results have, however, been obtained by an arrangement as shown in
Fig. 24, in which the active surface of the middle disc is not smooth, but
consists of a number of regularly spaced copper knobs or pegs, at the ends of
which the discharges take place at regular intervals. I have found that with
this arrangement each tram of oscillations may have a decrement as low as
In this way it is also possible to cause the groups of
oscillations radiated to reproduce a high and clear musical note in a receiver,
thereby making it easy to differentiate between the signals emanating from the
sending station and noises caused by atmospheric electrical discharges. By this
method very efficient resonance can be also obtained in appropriately designed
With regard to the receivers employed, important changes have taken place. By
far the larger portion of electric wave telegraphy was, until a few years ago,
conducted by means of some form or other of coherer, or variable contact either
requiring tapping or else self-restoring.
At the present day, however, I may say that at all the stations controlled by
my Company my magnetic receiver (Fig. 25) is almost exclusively
employed.22 This receiver is based on the decrease of magnetic
hysteresis which occurs in iron when under certain conditions this metal is
subjected to the effects of electrical waves of high frequency.
It has recently been found possible to increase the
sensitiveness of these receivers, and to employ them in connection with a
high-speed relay, so as to record messages at great speed.
A remarkable fact, not generally known, in regard to transmitters is, that none
of the arrangements employing condensers exceed in efficiency the plain
elevated aerial or vertical wire discharging to Earth through a spark gap, as
used in my first experiments (see Figs. 2 and 3).
I have also recently been able to confirm the statement made by Prof. Fleming
in his book The Principles of Electric Wave Telegraphy, 1906, page
555, that with a power of 8 watts in the aerial it is possible to communicate
to distances of over 100 miles.
I have also found that by this method, when using large aerials, it is possible
to send signals 2,000 miles across the Atlantic, with a smaller expenditure of
energy than by any other method known to myself.
The only drawback to this arrangement is, that unless very large aerials are
used, the amount of energy which can be efficiently employed is limited by the
potential beyond which brush discharges and the resistance of the spark gap
begin to dissipate a large proportion of the energy.
By means of spark gaps in compressed air and the addition of inductance coils
placed between the aerial and earth, the system can be made to radiate very
pure and slightly damped waves, eminently suitable for sharp tuning.
In regard to the general working of wireless telegraphy, the widespread
application of the system and the multiplicity of the stations have greatly
facilitated the observation of facts not easily explainable.
Thus it has been observed that an ordinary ship station, utilizing about 1/2
kilowatt of electrical energy, the normal range of which is not greater than
200 miles, will occasionally transmit messages across a distance of over 1,200
miles. It often occurs that a ship fails to communicate with a nearby station,
but can correspond with perfect ease with a distant one.
On many occasions last winter, the S.S. "Caronia" of the Cunard Line, carrying
a station utilizing about 1/2 kilowatt, when in the Mediterranean, off the
coast of Sicily, failed to obtain communication with the Italian stations, but
had no difficulty whatsoever in transmitting and receiving messages to and from
the coasts of England and Holland, although these latter stations were
considerably more than 1,000 miles away, and a large part of the continent of
Europe and the Alps lay between them and the ship.
Although high power stations are now used for communicating across the
Atlantic, and messages can be sent by day as well as by night, there still
exist short periods of daily occurrence, during which transmission from England
to America, or vice versa, is difficult. Thus in the morning and evening, when
in consequence of the difference in longitude, daylight or darkness extends
only part of the way across the ocean, the received signals are weak and
sometimes cease altogether. It would almost appear as if electric waves in
passing from dark space to illuminated space, and vice versa, were reflected in
such a manner as to be deviated from their normal path.
It is probable that these difficulties would not be experienced in telegraphing
over equal distances north and south, on about the same meridian, as in this
case the passage from daylight to darkness would occur almost simultaneously
over the whole distance between the two points.
Another curious result, on which hundreds of observations continued for years
leave no further doubt, is that regularly, for short periods, at sunrise and
sunset, and occasionally at other times, a shorter wave can be detected across
the Atlantic in preference to the longer wave normally employed.
Thus at Clifden and Glace Bay when sending on an ordinary coupled circuit
arranged so as to simultaneously radiate two waves, one 12,500 feet and the
other 14,700 feet, although the longer wave is the one usually received at the
other side of the ocean, regularly, about three hours after sunset at Clifden,
and three hours before sunrise at Glace Bay, the shorter wave alone was
received with remarkable strength, for a period of about one hour.
This effect occurred so regularly that the operators tuned their receivers to
the shorter wave at the times mentioned, as a matter of ordinary routine.
With regard to the utility of wireless telegraphy there is no doubt that its
use has become a necessity for the safety of shipping, all the principal liners
and warships being already equipped, its extension to less important ships
being only a matter of time, in view of the assistance it has provided in cases
Its application is also increasing as a means of communicating between outlying
islands, and also for the ordinary purposes of telegraphic communication
between villages and towns, especially in the colonies and in newly developed
However great may be the importance of wireless telegraphy to ships and
shipping, I believe it is destined to an equal position of importance in
furnishing efficient and economical communication between distant parts of the
world and in connecting European countries with their colonies and with
America. As a matter of fact, I am at the present time erecting a very large
power station for the Italian Government at Coltano, for the purpose of
communicating with the Italian colonies in East Africa, and with South
Whatever may be its present shortcomings and defects, there can be no doubt
that wireless telegraphy - even over great distances - has come to stay, and
will not only stay, but continue to advance.
If it should become possible to transmit waves right round the world, it may be
found that the electrical energy travelling round all parts of the globe may be
made to concentrate at the antipodes of the sending station. In this way it may
some day be possible for messages to be sent to such distant lands by means of
a very small amount of electrical energy, and therefore at a correspondingly
But I am leaving the regions of fact, and entering the regions of speculation,
which, however, with the knowledge we have gradually gained on the subject,
promise results both useful and instructive.
Not having the fortune of being conversant with the Swedish language, I have
thought it best, although an Italian, to use the medium of the English language
in delivering this address, as I know that English is more generally understood
here than Italian.
1. G. Marconi, Brit. Patent No. 12,039, June 2,
2. J. Inst. Elec. Engrs. (London), 28 (1899)
3.See letter of Dr. Lodge in The Times (London),
June 22, 1897.
4. A. Slaby, Die Funkentelegraphie, Verlag von
Leonhardt Simion, Berlin, 1897; see also A. Slaby, "The New Telegraphy",
The Century Magazine, 55 (1898) 867.
5. J. Inst. Elec. Engrs. (London), 28 (1899)
6. Brit. Patent No. 12,326, June 1, 1898; Brit.
Patent No. 6,982, April 1, 1899.
7. A. Blondel and G. Ferrie, "ètat actuel et Progrès de la
Tèlègraphie sans Fil", read at the Congrès International d'èlectricitè,
Paris, 1900; see also J. Soc. Arts, 49 (1901) 509.
8. Brit. Patent No. 7,777, April 26, 1900; see also
J. Soc. Arts, 49 (1901) 510-11.
9. See Letter of Prof. J. A. Fleming in The Times
(London), October 4, 1900.
10. PrOC. Roy. Soc. (London), 72 (May 28,
11. J.A. Fleming, The Principles of Electric Wave
Telegraphy, Longmans, Green & CO., London, 1906, p. 348.
12. J. Zenneck, Ann. Physik, , 23 (Sept. 1908)
846; Physik. Z., 9 (1908) 50, 553.
13. J. Soc. Arts, 49 (1901) 512.
14. G. Marconi, lecture before the Royal Institution of
Great Britain, June 13, 1902.
15. G. Marconi, "A Note on the Effect of Daylight upon the
Propagation of Electromagnetic Impulses", Proc. Roy. Soc. (London), 70
(June 12, 1902).
16. See also J. J. Thomson, "On Some Consequences, etc.",
Phil. Mag.,  4 (1902)
17. See Ref. 11, p. 618.
18. Riv. Marittima (Rome), October 1902.
19. G. Marconi, Paper read before the Royal Institution of
Great Britain, March 3, 1905.
20. See also G. Marconi, Lecture before the Royal
Institution of Great Britain, March 13, 1908.
21. G. Marconi, "On Methods whereby the Radiation of
Electric Waves may be mainly confined, etc.", Proc. Roy. Soc.
(London), A 77 (1906).
22. G. Marconi, "Note on a Magnetic Detector of Electric
Waves", Proc. Roy. Soc. (London), 70 (1902) 341.
Reginald Fessenden's amplitude modulation breaktrough.
From wireless telegraphy to wireless telephony.
More on Reginald Fessenden and Guglielmo Marconihere
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