Memories of Wilkes 1968.

By Winston Nickols,  Radio Technician.

Note the highlighted text in the paragraph beginning 'On the final run'.  It is a must read (site manager) 

 Diary entry,  March 6th, 1968. The Autumn Traverse from Wilkes Station, location Pfitzner Junction.

......"I was busy with the Echo Sounder until we stopped for the night. It was not working correctly although I had been assured that the new antenna, built by others while I was working at Repstat was OK. But it had not been tested. By nightfall and tea around 10pm  I was rather worried because without this equipment in operation there was no need for Group B to go any further. I worked until I was too tired to do any more and went to bed.

In the morning I checked each unit with the oscilloscope but everything seemed in order. By Tuesday evening I was convinced it could only be the antenna at fault so  made up some leads for the SWR bridge and prepared to work on the antenna next morning.

After being asleep for several hours I woke and read through the service data. I made a note to check several other waveforms and the transmit frequency, somehow, before looking at the antenna.

Awoke and had breakfast at 8.00am, dressed in windproofs and started checking the antenna. There was a strong wind with drift, the other sleds were barely visible.

I installed the SWR meter at the antenna, a three element yagi. The SWR was 3.5:1, the elements had been  cut for a frequency of 37Mhz. without  knowing  the actual transmitting frequency. Also the gamma matching rod seemed to be unusually long, almost a metre  when I would have expected it to be less than half that.

I cut two lengths of aluminium tubing, slit them lengthwise and slid them over the driven element.  The SWR reading for the lengthened element was worse, then tapped them in to shorten the overall length. There was a notable improvement in SWR.  So I  cut 150mm off each end of the driven element,   shortened the gamma matching bar and with the sliding pieces, was able to arrive at the optimum length and best SWR reading. I went inside and found a strong echo from the bedrock showing on the display, quite bright and clear enough to record on film.  Mike and Clive were pleased with the results but progress was impossible today as a blizzard had set in."

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 The Scott Polar Research Institute Radio Echo Sounder used a QQEO6/40 push-pull oscillator gated by a 3D12B from a 1200 volt supply and had a peak output of 100 watts.  The receiver was a solid state wideband TRF type.

Both units were controlled by a solid state keyer. For monitoring, two Tektronix oscilloscopes were used,  one provided for continual visual monitoring while the other  was set up for intensity modulation of the beam and scanning in one plane only, the resulting display showed the transmit pulse, a constant dot while an echo from the bedrock would appear as another spot, shifted to the right, varying in brightness and position in relation to the transmit pulse. A 35mm camera with a stepper motor film feed was mounted on this CRO and driven by an AC waveform from a trailing bicycle wheel with a hub dynamo. The antenna was  supported on a boom across the roof of the van, and beamed into the ground. Along with frequent micro-barometric surface measurements, an image of the bed-rock and ice thickness could be determined.      

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Later in the trip, one of the CROs failed and  kneeling on the floor of the R.M.I.T. fibreglass van, with my bunk as a workbench I had to trace and repair a brightness fluctuation fault.

As the traverse proceeded and temperatures fell, ( just south of Law Dome, our lowest temperature was -40C.)  a  solid state transmit HT delay circuit would fail to switch because of the cold, and had to be operated manually.

The most challenging job I faced ‘in the field’ came one day after most technical problems had finally been solved, or so I thought, when a major flash occurred in the transmitter cabinet. It turned out that a solid state -48 volt bias supply had failed. This in turn caused the large modulation valve to overheat, crack the glass and flash-over, destroying  the driver stage. Never did I imagine I would face such a fault in such a location, over 100Km from Wilkes.  But we had suitable parts with us and after many hours of work, the system was back in operation.

Life was rather rugged now. The caravan heater could not be used because   we could not clear the iced up chimney  and there was about three inches of ice covering the floor due to condensation. But on a lighter note, the meals (and chocolate cake)  cooked while lurching along in the van south of Law Dome were great. We lived well.

There was an annoying problem with the old faithful 'Angry 9' transceivers used for our twice daily skeds with VNJ on 2720Khz.  Non technical operators could never remember that there was a 2 second delay, after the transmit button was pressed, before they could be heard. (The transmit valve heaters had to warm up.) It was such a problem that I opened our two units up and modified them.

We spent part of Easter at the summit of Law Dome and it was here that Col asked me to check out the electrical side of the petrol fired cabin heater in the D4 tractor. I found the wiring Ok, but there was a fuel flow problem. After fixing this he left it running in an attempt to rid the cabin of ice. Some time later, in the main caravan, we heard a tremendous explosion. On rushing outside we saw clouds of black smoke billowing up from the D4. Grabbing extinguishers we rushed over to find .....no fire at all really. The cabin had become so hot that a pressure pack can of paint had burst, blowing paint over the windows, tool boxes etc and the fumes were being sucked into the turbine heater and burnt along with the petrol. The heater worked quite well!

On the final run back to Wilkes, along the coast from Cape Poinsett, I was alone and quietly reading in the large Freighters van being towed  by the D4 when the door burst open and in came Col, the driver. “Gee I’m hungry”  he said, and promptly made himself a sandwich. Then he leapt out the door and ran to catch up to the tractor and climbed back on.

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Back at the station there were always plenty of maintenance jobs to be done. Notable jobs were with the CTH7 transmitter. The remote tuning mechanical arrangement often gave trouble. It also had a habit of destroying an expensive Johnson vacuum tuning capacitor, when the 5kw. final stage would burst into oscillation. I investigated and found the neutralisation was a long way out of adjustment. To correct this I had to make up some test equipment, bridge the door interlock circuits and virtually climb inside the cabinet, with the high tension applied, to adjust the appropriate circuits.

The transmitter building, some distance from the main station was fed with three phase power via under-ice pyro. cables. Often, late in the year, an 70 amp fuse would blow in one of the generator rooms, on one of the feeders for the transmitter building. Replace the fuse and it would be OK for days. Finally a shortcircuit stayed on the cable  but where was the fault?

I built up a cable tracer and located the fault, a metre down in the ice, where a join had been made in the cable when it was laid. Water had found its way into a brass screw coupling device and brought on a short circuit.

One day OTC Sydney asked why we were transmitting such a broad signal. After some investigation, I found a retro fitted  two-tone oscillator in the ISB generator was rich in harmonics. I changed the design by building a new low distortion sine wave type. 

Whilst on a dog trip south of the station, I still remember the pain of hand cranking an ‘Angry 9’ transceiver when using the AM phone mode.

Our biggest ‘blow’ for the year came on Boxing Day. Winds of around 100 knots shook the station. Then a gust of 118 knots broke the anenometer. During the night heaps of snow entered the radio office through a fan vent. Late the following day I ventured out into the continuing gale.  Twelve antennas were down including all four transmitting rhombics, the NDB ‘flat-top’ as well as the ‘KOLD’ long-wire. All main receive antennas over the radio office were damaged.  The following afternoon a brief lull allowed repairs to be made to the most important antennas and Wilkes was back on the air. But the storm continued. All the snow had been blown away from around the station exposing jagged ice and we used cramp-ons to get around.

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And then in February, the USCGC ‘Southwind’ cut a path in for Thala Dan. It was my duty to lower the flag over Wilkes Station, Casey Station was officially opened and I was on my way home.......