the dawn of amateur radio in the u[1].k.(收音机雏形的诞生)-第4章
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Tesla had moved to Colorado Springs where he built his largest ever
coil which was 52 feet in diameter。 He studied all the different forms of
lightning in his unsuccessful quest for the transmission of power without
wires。
In Yugoslavia； Tesla is a national hero and a well…equipped museum
in Belgrade contains abundant proof of the genius of this extraordinary
man。
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The dawn of amateur radio in the U。K。 and Greece ： a personal view
CHAPTER TWO
THE BIRTH OF RADIO COMMUNICATIONS
By 1850 most of the basic electrical phenomena had been
investigated。 However； James Clerk Maxwell （1831…1879）； Professor of
Experimental Physics at Cambridge then came up with something entirely
new。 By some elegant mathematics he had shown the probable existence
of electromagnetic waves of radiation。 But it was twenty four years later
（eight years after Maxwell's death） that Heinrich Hertz （1857…1894） in
Germany gave a practical demonstration of the accuracy of this theory。 He
generated and detected electromagnetic waves across the length of his
laboratory on a wavelength of approximately one metre。 His own
photograph of the equipment he had set up can be seen in the Deutsches
Museum in Munich。
To detect the electromagnetic waves Hertz employed a simple form
of oscillator； which he termed a resonator。 But it was not sensitive enough
to detect waves at any great distance。 Before wireless telegraphy could
become practicable； a more delicate detector was necessary。
Credit is due to Edouard Branly （1844…1940） of France for producing
the first practical instrument for detecting Hertzian waves； the coherer。 It
consisted of two metal cylinders with leads attached； fitted tightly into the
interior of a glass tube containing iron or steel filings。 The instant an
electric discharge of any sort occurred the coherer became conductive； and
if it was tapped lightly its conducting property was immediately destroyed。
In practice the tapping was done automatically by a tapper which came
into action the moment the coherer became conductive。
In Russia the physicist Aleksandr Popov （1859…1905） had used a
coherer while engaged in the investigation of the effects of lightning
discharges。 He suggested that such discharges could possibly be used for
signaling over long distances。 Old timers may remember that about 50
years ago Russian amateurs used to send out a QSL card with a drawing of
Popov and a caption which claimed that he was 'the inventor of radio'。
In Italy； a young 22…year…old electrician became interested in
electromagnetic radiation after reading papers by Professor Augusto Righi
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The dawn of amateur radio in the U。K。 and Greece ： a personal view
（1850…1921）。 It was Guglielmo Marconi （1874…1937）； the son of a well…to…
do landowner who lived in Bologna； and who was married to Annie
Jameson of the well known Irish Whiskey family。 Guglielmo； their second
son； had his early education at a private school in Bedford； England； and
later at Livorno and Florence in Italy。 When he read about the experiments
of Heinrich Hertz and about Popov's suggestion； he saw the possibility of
using these waves as a means of signaling。 His first transmitter； shown in
the accompanying photograph； did not radiate very far。 When he folded
the metal plate into a cylinder and placed it on a pole 30 feet above the
induction coil and connected to it by a vertical wire； he was able to detect
the radiation nearly two kilometres away。 Marconi realised that his
signaling system would be most useful to shipping； and in those days
England possessed the world's greatest navy and the world's biggest
merchant fleet。
The Italian government was not interested in young Marconi's work；
so after a family conference he was brought to London by his mother； who
had influential relatives there。 Not only did they finance his early
experiments but they also put him in touch with the right sort of people。
One of these was Alan A。 Campbell Swinton who became the first
President of the Radio Society of London （now the R。S。G。B。） many years
later； in 1913。 Campbell Swinton introduced the young Italian to William
Preece； then Engineer…in…Chief of the British Post Office。 Preece had
already been investigating various methods of 'induction' telegraphy。
In a book entitled Wireless Telegraphy published in 1908； William
J。White of the Engineer…in…Chief's department at the G。P。O。 wrote；
〃The work of Sir （then Mr） William Preece； important though it was；
did not attract the attention of the public to the extent that might have been
expected。 This was due to the fact that no sooner had he demonstrated a
method of wireless telegraphy which was a commercial possibility than
his system was superseded by another； and a better one； brought to
England by Mr Guglielmo Marconi in 1896。 The possibilities of Mr
Marconi's system were at once recognised by Mr William Preece。 The
experience of the elder and the genius of the younger man； who must be
given the credit of having devised the first practical system for wireless
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The dawn of amateur radio in the U。K。 and Greece ： a personal view
telegraphy； combined to turn apparently disastrous failures into success；
and now （in 1908）； wireless telegraphy has become； in less than a decade；
part and parcel of commercial and national life。〃
The world's first patent for wireless telegraphy was awarded to
Marconi on the 2nd June 1896。 In it he stated that 〃electrical action can be
transmitted through the earth； air or water； by means of oscillations of high
frequency。〃 In the first public demonstration of his equipment Marconi
spanned the 365 metres between the G。P。O。 and Victoria street。 Later； on
Salisbury Plain； in March 1897； his signals were detected over 7
kilometres away。 On the 11th & 18th May 1897 messages were first
exchanged over water。 On the 27th of March 1899； during naval
manoeuvres； Marconi bridged the English Channel for the first time； a
distance of about 140 kilometres。 His transatlantic triumph came on the
12th December 1901 when the morse letter 'S' was transmitted from
Poldhu； in Cornwall and received by Marconi himself at St。 John's；
Newfoundland； who recorded the historic event in his pocket book simply
〃Sigs at 12。20； 1。10 & 2。20〃。
The operation of Marconi's transmitter was itself quite spectacular。 To
produce the oscillations he employed the oscillator designed by Augusto
Righi。 Depressing the key closed the circuit and brought the inductor coil
into action。 Vivid sparks occurred between the balls of the oscillator； to the
accompaniment of a succession of sharp cracks； like the reports of a pistol；
and some energy was sent off the square metal plate in the form of t
