Life After OTC

Robert Brand Part 2

The Wireless Institute of Australia Magazine Article WMBD

Below is some of the article on the Echoes of Apollo World Moon Bounce Day (WMBD). Much of it was written by the University of Tasmania (UTAS) staff members Rex Moncur VK7MO and Justin Giles-Clark VK7TW for the Wireless Institute of Australia (WIA):

27 June 2009 was designated World Moon Bounce Day as an amateur radio contribution to the celebrations of the 40th anniversary of man’s first landing on the moon. The event was organized by Echoes of Apollo – a joint project between Pat Bathelow (US) and Robert Brand (Australia). Key to the success of the event was the contribution of the Overseas Telecommunications Veterans Association. (OTVA) A key objective was to involve and interest school children in science and amateur radio by allowing children to hear voices from the moon. The event was supplemented by amateur Earth Moon Earth (EME) stations all around the world and particularly those with SSB capability on 23 cm.

Within Australia the University of Tasmania agreed to take part using their 26 metre dish which was originally used by NASA in the Orroral Valley near Canberra between 1964-1985 after which it was gifted to the University and transported to Mt Pleasant, near Richmond in southern Tasmania. Our involvement was to provide amateur EME equipment, help set up and test the system and operate the station on the day. As it eventuated the availability of large dishes provided the opportunity to explore QRP EME at as low a level as possible and we are pleased to report completion of a JT65 EME contact between the University of Tasmania’s 26 metre dish and a Dutch 25 metre dish, PI9CAM, with the Tasmanian end running only three milliwatts.

Mount Pleasant Radio Telescope UTAS

Setting up the University of Tasmania dish

While Dr Jim Lovell of the University of Tasmania willingly offered their dish and the support of the site technician Eric Baynes (VK7BB) it was first necessary to consider what was practical. At our first meeting it became clear that transmitting any sort of high power as required for SSB would be out of the question as the dish is fitted with five extremely sensitive liquid helium cooled receivers working from 4 to 22 GHz. There is no protection for RF and we could not risk damage to these receivers which are involved in ongoing international research programs. Accordingly, the Echoes of Apollo team where advised that we would contribute to the event but as a receive station only.

40 Year Anniversary Apollo 11The feeds and receivers for the 26 metre dish are mounted in a small feed cabin (a cube approximately two metres per side) behind a Teflon window approximately one metre in diameter. Within the cabin there is a remotely controlled three axis focus frame that allows the feeds and receivers to be moved into the correct focal position depending on which feed is in use. There is space for a two GHz non-cooled feed and receiver which fortunately was not required around the time of the Echoes of Apollo event and the University agreed that this could be removed and replaced with a 23 cm antenna. Because of space limitations it was decided to use a small three turn helical. There is over 100 metres of LDF-4-50 coax between the dish and the control building where we could operate and for this reason we decided to down-convert at the feed and receive on 144 MHz. Eric constructed a down-converter and the VK7MO EME station provided pre-amplifiers, 144 MHz receiver, GPS frequency reference, computer running WSJT and bandpass filters at 1296 MHz and 144 MHz to limit interference from microwave systems at the nearby Hobart airport.

A few weeks prior to the event tests were conducted with Dave VK2JDS, with JT65c signal levels much worse than expected at -9 dB and no prospect of copying SSB. A sun noise test gave around 18 dB compared to 27 to 28 dB determined with the VK3UM EME calculator. The time for testing was limited as this is an operational radio astronomy research facility but the system was gradually refined with additional pre-amps and filters and through adjusting levels at all stages – as well as resolving the occasional “Murphy” problem. Finally we decided that the helical feed must be the remaining limitation and did some estimates to see if a Septum feed and choke ring could be physically mounted. Initially it fouled other equipment but after a redesign of the mount is was successfully installed. In the end we achieved a sun noise of 25 dB which was within a few dB of what could be expected. Every time the system needed adjustment Eric had to don a safety harness and go up in a cherry picker .

The story above is part of the article in the Amateur Radio magazine, a publication of the Wireless Institute of Australia.

OTVA LogoMuch of the credit for the 2009 World Moon Bounce Day success can be directly attributed to the efforts of the OTVA and other exOTC staff. This has been a fantastic experience and we are looking to grow the 2010 World Moon Bounce Day to even great success. Yes, a world first for OTC staff involvement and a world record! Plenty of Australian amateur radio people got involved and were active bouncing their signals off the moon. I am Now organising the 2010 World Moon Bounce Day for early April. If you wish to help, feel free to raise your hand. This year we will have massive radio and TV coverage in Australia.

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