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Doug McArthur

History of the VK3UM Dish

The parabolic reflector (dish) was manufactured by D.S.Kennedy & Co Cohasset, Massachusetts in 1963 and was purchased by the then Australian Postmasters Generals Department (PMG), through the Australian agents Electronic Industries Ltd, Sturt Street South Melbourne about that time.

Mine, was one of ten such antennae purchased, and these were installed at Dunn’s Hill, Melbourne (2),  Flinders Island in Bass Straight (4), and near Launceston  (2), Tasmania. The other two was held as a spares in Melbourne.

The installation of the antennae and the equipment was completed late in 1963 for the purpose of conducting propagation studies across Bass Straight. (Melbourne to Tasmania via Flinders Island). The equipment operated between 2-3 GHz and provided for analysis of space, frequency and polarity transmissions. The research study was conducted by the Telecom Research Division located at Clayton Victoria.

It is unknown just how long the experiments ran for but the dishes remained un used for many years and the surrounding foliage grew and partly obscured those on One Tree Hill. The dishes on Flinders Island and Tasmania were believed to have been sold for scrap aluminium during this period.

The two spares were sold to an amateur in Adelaide. One of them was damaged and was on sold to a person unknown in Melbourne.

After many months negotiation I finally was able to purchase the remaining intact dish at One Tree Hill (the other had had its petals removed) on the 28th January 1997

Just after it was purchased a major bush fire went through the very location. Many homes were lost around the perimeter and miraculously the fire did not turn my purchase into an aluminium ingot!

Assisted by Brian Dodgson (VK3BD), Trevor Pitman (VK3VG), John Verges, Rob (Son in Law) and my son Peter, we dissembled the dish and transported it back to “Tikaluna” a few weeks later.

I am most fortunate to have as a neighbour, Geoff Osborn, an accomplished welder (and everything else) who had a large workshop. It was here that the support structure was built and finally transported up the hill.

There were a few aberrations along the way to its final commissioning! Firstly I had a severe stroke on 25 October 1999 and it took almost 2 years to become mobile again but, with great assistance from Trevor and Brian, who spurred me on, it provided an incentive towards my recovery.

Along the way we had a huge storm, with winds exceeding 160 kph, and it picked the dish up (it was awaiting final attachment to the bottom structure) and moved it some 30 metres to the leeward side of the hill. It was a very near thing as the ridge line is narrow and a few more metres and I would have lost the lot.

The first QSO took place on 432.018 MHz at 1300z on 26 July 2001 with SM2CEW.

Installed Specifications

Concrete footings .. 18 cubic metres vibrated and compacted.

Dish Mount .. Centurion Tank Ring Gear (1200 kg)

Rated to withstand for winds up to 180 kph in the ‘bird bath’ position. It does not move more than 0.1 degree at winds of 80 kph in either Azimuth or Elevation and auto tracking is possible down to 0.1 degrees absolute.

View Dish Details from the Handbook

View Original Advertising brochure .. it was designed to be a ‘portable tow able installation.

The welding and construction accuracy of the dish is simply amazing given the time when it was made. A brilliant piece of engineering for its day .. or even today! It is fully compliant to 7.5 GHz and ‘usable’ at 10 Ghz.