the dawn of amateur radio in the u[1].k.(收音机雏形的诞生)-第24节
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Balkans and the countries of the Middle East； there are two rotatable log
periodic antennas with a high angle of vertical radiation （45 degrees） and a
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wide angle of 32 degrees in the horizontal plane。
The remotely controlled switching centre allows each of the two
transmitters to be connected to any one of the 23 antennas。
Electromechanical protection circuits ensure that a transmitter can only be
connected to an antenna that is tuned to the same frequency。 The change of
antennas and transmitting frequencies is made during the ten…minute
interval between programmes； which always begin on the hour； preceded
by the now familiar signature tune of a shepherd playing his flute with the
tinkling of sheep…bells in the background； recorded in 1936； followed by
the Greek National Anthem。
The special programmes of news and features originate in the
broadcasting headquarters in Athens and go on the air throughout the 24
hours of the day in Greek； English and many foreign languages。 Reports of
reception are welcome and should be addressed to K。E。B。A。； Avlis； Greece。
（The Greek initials stand for short wave transmitting centre。）
But Avlis was ‘in the news' long before the Greek broadcasting
service decided to install its short wave transmitters there。 In ancient times
a great fleet of ships had been assembled in the harbour there； ready to set
sail for Troy； following the abduction of the beautiful Helen of Sparta by
Paris； the young Prince of Troy。 But there had been no wind for many
weeks； and the sea was dead calm。
Agamemnon； the King of Mycenae； who had himself contributed
over 100 ships to the fleet； decided to consult his Seer。 As was the custom；
the Seer slaughtered a young lamb and scrutinised its entrails。 He then
announced that the wind would come up if Agamemnon sacrificed his
daughter Iphigenia on the Altar of Sacrifice。 King Agamemnon despatched
a messenger to Mycenae （no VHF repeater being available in those days）
to tell his wife Queen Klitemnestra to send their daughter Iphigenia to
Avlis （Aulis）。 The King said he was planning to marry her off to Achilles；
the most eligible bachelor of the day。 When poor Iphigenia arrived she was
quickly placed on the Sacrificial Altar … and had her pretty throat slit。
However； there seems to be another version to the end of the story。
Just before the human sacrifice was due to be made Artemis （Diana； the
famous Goddess of Hunting） sent a small deer which was placed on the
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altar instead of the girl。 Iphigenia was secretly spirited away to Taurida； in
northern Greece； and put in charge of Diana's temple there。
（This story is the subject of a well…known classical Greek play。）
Historical note on the Marconi…Stille steel tape recording machine。
At the beginning of the century Professor Poulsen； one of radio's
earliest pioneers； discovered that a magnetic impression could be made on
a moving length of wire which remained on the wire even after it had been
rolled up。 He used his machine to record the Morse code only； that is
magnetism ‘on' and ‘off'。 In 1924 Dr。 Stille in Germany made a machine
which could record sounds。 The B。B。C。 sent two engineers to Berlin； and
after a demonstration they offered to buy the machine； but in the end they
returned to England empty…handed。
In 1931 Mr Louis Blattner managed to buy a machine and bring it to
England。 He called it the Blattnerphone。 By this time Dr。 Stille had
replaced Poulsen's wire with a flat steel tape 6 mm wide。 Each reel of tape
could only accommodate 20 minutes of recording。 There was a constant
and heavy background hiss； due to the inherent quality of the steel tape
itself。
Stille Inventions Ltd。 joined forces with Marconi's Wireless
Telegraph Co。 Ltd。 to produce； with the close co…operation of the B。B。C。
Research Department； the Marconi…Stille machine which was put into use
in 1934。 The tape width was reduced to 3 mm and the thickness to only
0。08 of a millimetre。 In order to secure the reproduction of the higher
audio frequencies； it was found necessary to run the tape at a rate of 90
metres per minute past the recording and reproducing heads。 This meant
that the length of tape required for a half…hour's programme was nearly 3
kilometres！
4。 Brief description of the ribbon or velocity microphone。
George Papandreou； Greek Prime Minister of the war…time
government of National Unity in exile； is seen with the famous ribbon
microphone developed by the B。B。C。 in 1934。 This microphone （R。C。A。
designation 44BX） consists of a ribbon of corrugated aluminium foil only
0。0002 of an inch thick suspended vertically in a very intense but narrow
magnetic field。 When sounds vibrate the ribbon extremely low alternating
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voltages are developed at the ends of the ribbon； which has a very low
impedance of only 0。15 ohm； necessitating the use of a step…up
transformer of 1：45 turns ratio very close to it。 The frequency response is
20 to 16；000 Hz。 A drawback is that the ribbon can be blown out of the
magnetic gap by sudden puffs of air when a speaker gets too close to the
microphone； so the casing is lined with several layers of chiffon which let
in the sounds but not the air。 Without its base the ribbon microphone
weighs 4 kilograms； nearly 9 lbs。
5。 An outstanding antenna system designed by Rex G4JUJ for Phase
III amateur satellite communication。
The up…link section comprises four 88…element Jaybeam multi… beams
which provide a power gain of 225。
The two down…link 8 element yagis are each fitted with a small D。C。
motor directly coupled to a 9 inch length of M5 brass studding rotating
inside a block of PTFE linked to a push rod which can move the antennas
75 degrees both sides of the vertical position； either in unison or in
opposite directions。 This system provides infinitely variable polarisation
which optimises the down…link signal at any instant。
6。 The saga of H。H。M。S。ADRIAS
While fighting in the area of the Dodecanese Islands on the night of
the 22nd October 1943 the destroyer ADRIAS （L67） was seriously
damaged by a mine but refused to sink。
Under the command of Commander John Toumbas the ship covered a
distance of approximately 700 nautical miles； reaching the port of
Alexandria in Egypt on the eve of the feast of Saint Nicholas； the patron
saint of all seamen。
The Greek Minister of the Navy Sofoclis Venizelos； and the British
Admiral in command of the Royal Navy in the Eastern Mediterranean；
provided an honorary escort for the brave little ship that had refused to die。
A few months later the snub…nosed L67 joined the fleet of 100 vessels of
all sorts which sailed to Greece for the Liberation。
The photographs were taken by the author （with the exception of the
damaged L67） who travelled back to Greece on H。H。M。S。 AVEROF in the
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same convoy。 The photograph of L84； a similar type destroyer to ADRIAS
shows how much of her bows was blown off by the collision with the
mine。
（H。H。M。S。 stands for His Hellenic Majesty's Ship。）
7。 German sabotage at the Cable & Wireless station at Pallini； Greece；
in World War II。
As the German army was pulling out of Greece in October 1944 its
engineers carried out extensive sabotage to installations of a strategic
value。 At Pallini； not far from Athens； an attempt was made to destroy the
transmitter hall by dropping one of the antenna towers onto it； but the
equipment was not damaged。
They w
