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 only0.08 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 alternatingvoltages 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 ******* 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 antennas75 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 thesame 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 were more successful at the Royal Navy transmitting site at Votanikos.Here they tried to destroy six 300 foot tubular masts.One remained standing and also the lower part of another.All the test gear in the lab was thrown out of a second floor window and burnt.I was acting as official photographer for my unit at the time.When I walked into a small store room I saw all the equipment had been thrown off the shelves on to the floor, but appeared to be intact.I spotted a box of brand new packed German navy morse keys and decided the time had come for me to acquire a small war trophy of my own.As I bent down to pick up a key, I was horrified to see two large sticks of gelignite perched perilously on the edge of a shelf.The explosive was tied with white ribbon, with a weight attached to the other end.I froze to the spot.Gingerly I lifted my trophy out of the box and began to walk slowly backwards, being very careful not to knock anything over.I breathed a sigh of relief when I was out of the room and immediately alerted the engineers who came and defused the booby trap.So this book might never have been written thanks to the German army.
