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beater’s rolling machine, until it was about 2.5 mm thick. It was then annealed to make it soft enough to be wound into a tight spiral. Initially I made the temporary coil formers out of medium density fibre- board (MDF), but they were not solid enough when grooves were routed into them, to hold the copper pipe in the spi- ral shape. However this proved that the idea would work. Brian Harvey had some more paper bakelite sheet that I was able to shape into six-arm formers for this coil, and the coils for the vari- ometer, part of the antennae matching unit. Jig to rout the grooves in the coil formers. I made a jig to hold the former shapes on a sliding platform with the router fixed above it. A long screw advanced the platform holding the for- mer 2 mm for one turn, as the former was rotated 60 degrees, making grooves 12 mm apart, in each arm of the face of the former. The formers were bolted to another sheet of wood and the copper strip wound from the tight inside diameter to the larger outside. Each turn was held in place by a lot of bolts and washers until the other face of the former was placed on top, and the copper strip Flattened copper strip held temporarily in spiral coil shape. manipulated into all the matching grooves. When the former sides were fixed together, all the temporary holding bolts were removed. From the circuits I had found in the German Telefunken catalogues, I was Transmitter unit. able to figure out how the transmitter section was connected. The spark gap was operated by a large voltage (8,000 volts) applied to the unit, from a trans- former that had 220 volts at 500 cycles per second (c.p.s.) applied to the pri- mary winding of the transformer, when the morse key was operated. This gener- ated a spark with a tone of 500 c.p.s. which could be distinguished by the receiving station from the normal atmospheric electrical static and light- ning-generated noise received on Macquarie Island. The transformer in the replica was made to this shape by soldering a piece of tinplate around two oval-shaped empty herrings tins. The top was rein- forced with a heavier piece of steel and the insulators fitted on top. These parts were then mounted on a wooden block, with wires passing underneath, for the morse key to operate a relay under the bench. The variometer unit was made using three spiral coils, made in the same way as those for the tuning coil for the trans- mitter. This unit is used to ‘impedance match’ the transmitter to the aerial sys- tem, so that the maximum power is transmitted towards the receiving sta- tion. It works by making the magnetic fields of the coils interact, making the total inductance appear larger or small- er, depending on their connection and position of the coils. Once they are posi- tioned for the maximum power transfer, they are locked in position by a large nut on the axis of the coils. Three coils of the variometer unit. Mawson’s Telefunken receiver unit The Telefunken receiver unit was a tuned primary, crystal set. The photo- graph, taken by Hurley, of Walter Hannam in front of the wireless set at Commonwealth Bay, just shows the top front of the receiver unit, with the cou- pling coils visible. There is a panel propped in front of and hiding the tun- ing capacitor, which is shown in the fol- lowing Telefunken catalogue picture of a 1911 model receiver. I was puzzled for a long time as to what this panel was, but recently found some pictures on the internet of a mul- tiple detector panel. This was a unit with a number of different types of crystal Telefunken catalogue picture of 1911 model crystal set. Walter Hannam at the wireless in 1912. — Photo by Frank Hurley. Aurora - June 2012 - Page 15