Wireless Telegraphy in Australia is a history of early radio communications efforts between Australia and England. It makes me think of the opening of the movie Dr. No where the Bermuda agent is assassinated as his secretary opens the radio link to London. There were large installations involved in transcontinental communications, even up through the sixties.
The highest speed at which commercial telegraph traffic had been handled over the Australia-England circuit was 325 words per minute, and this limit was imposed by the mechanical restrictions of the automatic sending and recording instruments at each end. However, under normal conditions, the circuit operated at speeds between 150 and 200 words per minute, and increased capacity was usually handled by additional transmitters.
Communication with London and Montreal, which provide the outlets for the exchange of messages with Europe and the American Continent respectively, was conducted alternately over the long or short portion of the great circles connecting Melbourne with those points, according to which portion of the route was in darkness.
The short route over each of the great circles approximates 9,000 nautical miles, and the long route a little more than 12,000 nautical miles. The average number of hours per day suitable for high speed duplex communication between Melbourne and London was about 17, the period being longest in the winter, when on many days it was practically continuous.
World War I was an initial incentive to find ways to communicate that didn’t depend upon under sea cables. That was in the longwave era. Up to World War II, the use of short waves was developed and 25 meters was found to be a good choice for globe hopping communications. This was also when the ionosphere was discovered and its properties investigated.
At its peak, the station had three 25 Kw HF transmitters, with 94 antennas. There were three steel lattice masts, 75 metres high, and 195 metres apart, each weighing 50 tons. The guy wires were supported by concrete blocks, 33 metres from the base of each tower.
The entire antenna structure ran in an East-West direction, and supported crossarms of 27 metres in length. The azimuth was about 330 degrees, which was the short path to Europe. The same antennas were used at about 120 degrees, for longpath.
The operating frequency was in the 12 MHz region, using some interesting circuit designs! The generator actually produced the carrier, at around 12 MHz – there were no RF oscillators or crystal controlled devices. The system was essentially a huge AC generator!
The story is a personal one on the VK3JQ/VK3KCM website. That website is dedicated to “Amateur Radio, Care and feeding of Collins Amateur Radio equipment, The history of the Collins Radio Company in Australia and Amalgamated Wireless Australasia.”
– do I remember the days when the KWM2 was premium mobile equipment! Ian has a footnote that really rings a bell: “When working with receivers, transmitters and RF amplifiers, a thing to remember is that unlike DC, RF circuits some times defy logic. You may notice that an RF circuit may appear both physically and electrically perfect but refuses to function as expected. This is the nature of RF. The position of a wire, component or shield can make a lot of difference in the operation of an RF stage.”
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