the dawn of amateur radio in the u[1].k.(收音机雏形的诞生)-第3章
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which he took out in the U。S。A。 in 1890 ultimately led to the design of the
humble ignition coil which energises billions and billions of spark plugs in
all the motor cars of the world。 His American patents fill a book two
inches thick。 His name was Nicola Tesla （1856…1943）。
Nicola Tesla was born in a small village in Croatia which at that time
formed part of the great Austro…Hungarian Empire。 Today it is a northern
province of Yugoslavia； a state created after the 1914…1918 war。 Tesla
studied at the Graz Technical University and later in Budapest。 Early in his
studies he had the idea that a way had to be found to run electric motors
directly from A。C。 generators。 His professor in Graz had assured him
categorically that this was not possible。 But young Tesla was not
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convinced。 When he went to Budapest he got a job in the Central
Telegraph Office； and one evening in 1882； as he was sitting on a bench in
the City Park he had an inspiration which ultimately led to the solution of
the problem。
Tesla remembered a poem by the German poet Goethe about the sun
which supports life on the earth and when the day is over moves on to give
life to the other side of the globe。 He picked up a twig and began to
scratch a drawing on the soil in front of him。 He drew four coils arranged
symmetrically round the circumference of a circle。 In the centre he drew a
rotor or armature。 As each coil in turn was energised it attracted the rotor
towards it and the rotary motion was established。 When he constructed the
first practical models he used eight； sixteen and even more coils。 The
simple drawing on the ground led to the design of the first induction motor
driven directly by A。C。electricity。
Tesla emigrated to the U。S。A。 in 1884。 During the first year he filed
no less than 30 patents mostly in relation to the generation and distribution
of A。C。 mains electricity。 He designed and built his ‘A。C。 Polyphase
System' which generated three…phase alternating current at 25 Hz。 One
particular unit delivered 422 amperes at 12；000 volts。 The beauty of this
system was that the voltage could be stepped down using transformers for
local use； or stepped up to many thousands of volts for transmission over
long distances through relatively thin conductors。 Edison's generating
stations were incapable of any such thing。
Tesla signed a lucrative contract with the famous railway engineer
George Westinghouse； the inventor of the Westinghouse Air Brake which
is used by most railways all over the world to the present day。 Their
generating station was put into service in 1895 and was called the Niagara
Falls Electricity Generating Company。 It supplied power for the
Westinghouse network of trains and also for an industrial complex in
Buffalo； New York。
After ten years Tesla began to experiment with high frequencies。 The
Tesla Coil which he had patented in 1890 was capable of raising voltages
to unheard of levels such as 300；000 volts。 Edison； who was still
generating D。C。； claimed A。C。 was dangerous and to prove it contracted
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with the government to produce the first electric chair using A。C。 for the
execution of murderers condemned to death。 When it was first used it was
a ghastly flop。 The condemned man moaned and groaned and foamed at
the mouth。 After four minutes of repeated application of the A。C。voltage
smoke began to come out of his back。 It was obvious that the victim had
suffered a horribly drawn…out death。
Tesla said he could prove that A。C。 was not dangerous。 He gave a
demonstration of high voltage electricity flowing harmlessly over his body。
But in reality； he cheated； because he had used a frequency of 10；000
cycles （10 kHz） at extremely low current and because of the skin effect
suffered no harm。
One of Tesla's patents related to a system of lighting using glass tubes
filled with fluorine （not neon） excited by H。F。voltages。 His workshop was
lit by this method。 Several years before Wilhelm Roentgen demonstrated
his system of X…rays Tesla had been taking photographs of the bones in his
hand and his foot from up to 40 feet away using H。F。currents。
More astonishing still is the fact that in 1893； two years before
Marconi demonstrated his system of wireless signaling； Tesla had built a
model boat in which he combined power to drive it with radio control and
robotics。 He put the small boat in a lake in Madison Square Gardens in
New York。 Standing on the shore with a control box； he invited onlookers
to suggest movements。 He was able to make the boat go forwards and
backwards and round in circles。 We all know how model cars and aircraft
are controlled by radio today； but when Tesla did it a century ago the
motor car had not been invented； and the only method by which man could
cover long distances was on horseback！
Many people believe that a modification of Tesla's ‘Magnifying
Transmitter' was used by the Soviet Union when suddenly one day in
October 1976 they produced an amazing noise which blotted out all radio
transmissions between 6 and 20 MHz。 （The Woodpecker） The B。B。C。； the
N。B。C。 and most broadcasting and telecommunication organisations of the
world complained to Moscow （the noise had persisted continuously for 10
hours on the first day）； but all the Russians would say in reply was that
they were carrying out an experiment。 At first nobody seemed to know
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what they were doing because it was obviously not intended as another
form of jamming of foreign broadcasts； an old Russian custom as we all
know。
It is believed that in the pursuit of his life's ambition to send power
through the earth without the use of wires； Tesla had achieved a small
measure of success at E。L。F。 （extremely low frequencies） of the order of 7
to 12 Hz。 These frequencies are at present used by the military for
communicating with submarines submerged in the oceans of the world。
Tesla's career and private life have remained something of a mystery。
He lived alone and shunned public life。 He never read any of his papers
before academic institutions； though he was friendly with some journalists
who wrote sensational stories about him。 They said he was terrified of
microbes and that when he ate out at a restaurant he would ask for a
number of clean napkins to wipe the cutlery and the glasses he drank out
of。 For the last 20 years of his life until he died during World War II in
1943 he lived the life of a semi…recluse； with a pigeon as his only
companion。 A disastrous fire had destroyed his workshops and many of his
experimental models and all his papers were lost for ever。
Tesla had moved to Colorado Springs where he built his l
