Amateur Radio September 2008
Delivery expected from 2 September
Editorial
Spring is almost here
As you read this, spring has officially arrived. It is hard to believe here in Churchill, after more than a week of very cold and wet weather blowing up from the Southern Ocean. I am really not complaining: we can certainly do with lots more rain, provided it arrives in only moderate quantities on each occasion.
With September comes the equinox and the chance of extended propagation on the VHF bands via various ionospheric modes. “Magic Band” aficionados will be listening as much as possible, intent on catching any opportunity that may arise.
Contests and activations
The Remembrance Day Contest is happening as I write, as is the International Lighthouse/Lightship Weekend. Coming up is the ALARA Contest. Yes it is fun to just participate in a Contest (or an event such as the ILLW). But do send in your log, especially for the RD Contest – every point counts for your home state.
The Shack in Winter
Many have been tackling various projects on the cold winter days. The weather has not been good here in Victoria for antenna projects or outdoor tasks. Many will have taken the opportunity to tackle indoor construction projects, as evidenced by at least a couple of VHF amateurs in this issue.
Well known microwave operator Alan Devlin VK3XPD shows us what can be done in repurposing ex-commercial equipment – just look at the cover and inside back cover! Having previously operated 10 and 5.7 GHz EME (Earth-Moon-Earth) from his house in Burwood, Alan has recently commissioned a 10 GHz transverter system for terrestrial operations. With the local oscillator chain referenced to a GPS locked 10 MHz oscillator, Alan will have overcome one of the key potential stumbling blocks for microwave operations – am I on frequency? It is common for errors of several to tens of kilohertz to be observed in transverter systems. And that is just with your equipment. Add the same uncertainty to the contact station, together with antenna pointing requirements, and sometimes you may not make contact, even with care by both operators. Having solved this, at least at his location, Alan has mounted the transverter system almost at the feedpoint of the dish antenna (just behind the dish). But he has also mounted the dish on a fully steerable azimuth-elevation mount. How long will it be until we see some long distance rainscatter or troposcatter contacts?
The VHF/UHF column shows some brief reports of experiments between Rex VK7MO in Hobart and Rhett VK3VHF at Bairnsdale. Both now run their IC-910 transceivers with the master oscillators locked to a GPS reference. The increased accuracy of the operating frequencies means that these operators can begin to explore new limits of station performance and propagation, as evidenced by the recording displayed in this month’s column. I am sure that many more weak-signal VHF and UHF operators will be moving toward similar schemes, especially following the discussion of this topic at GippsTech back in July.
As more operators explore the possibilities of digital modulation and demodulation schemes, one can only wonder how long it will be before the major equipment manufacturers include a 10 MHz reference input/output port on all their transceivers? Icom has provided such a port on the IC-7700, reviewed last month. How about the IC-910H, the IC-7000, and equivalent radios from the other manufacturers? Not every amateur will demand such performance for everyday operation, but many are already exploring how to modify their equipment so that it meets their needs.
More spring
September: football finals, soccer season starting, the end of the VK snow season. Your last opportunity to work the special Olympic stations in China. Time to prepare for coming contests. Then it is not too far until Christmas – where did those last few months go?
Get ready for the improving weather and hopefully improving propagation on HF – surely it must come soon?
73, Peter VK3KAI
Cover
The cover photo this month shows the 10 GHz transverter system mounted at the antenna at the home of Alan Devlin VK3XPD. Located in Burwood in Melbourne’s eastern suburbs, Alan is ready to explore just what may be possible using the 10 GHz band. Also look at the inside back cover for more views of Alan’s gear: you can see part of the three metre diameter dish that Alan uses for EME operation, and part of the internal workings of the transverter mounted in the radome behind the small dish that features on the cover. Photograph by Alan Devlin VK3XPD.
Table Of Contents
GENERAL
2008 Victorian ARDF Championships Report Jack Bramham VK3WWW
Working Mildura on 2.4 GHz Chas Gnaccarini VK3PY
Crystal Clear - Communications technology in WW II by Richard J Thompson Reviewed by Peter Holtham VK4COZ
Disaster communications Sichuan earthquake and GAREC-08 Jim Linton VK3PC
The ham trip of a lifetime J.A. (Tony) Hutchison VK5ZAI
WICEN Tasmania (South) goes Horseback Roger Nichols VK7ARN
TECHNICAL
A 50 W CW transmitter for 137 kHz Drew Diamond VK3XU
Simple wideband Yagis for 2 m and 70 cm Paul McMahon VK3DIP
A Power Distribution Box Using Anderson Powerpoles Henrik Stenstrom VK2HHS
Disaster communications Sichuan earthquake and GAREC-08
Author: Jim Linton VK3PC
The author, Jim Linton VK3PC is Chairman of the IARU Region 3, Disaster Communications Committee, and this article details the work done by radio amateurs directly after this earthquake wreaked so much destruction throughout Sichuan Province and surrounding areas of China in May, 2008.
In particular, it is a story of some ‘success’ amidst so much sorrow, in that the relatively new Chinese amateur radio presence, ably directed by the CRSA (Chinese Radio Sports Association) was able to provide so much positive, appropriate assistance when much, if not all, of the commercial communications and rescue infrastructure had been rendered inoperable.
The moral of the story, from an amateur radio standpoint, is that we should be forever vigilant in our disaster preparations – we never, ever, really know when next our resources will be called upon.
The ham trip of a lifetime
Author: J.A. (Tony) Hutchison VK5ZAI
Many VK amateurs harbour Walter Mitty type dreams of a trip overseas, and encompassing as many of the chosen sites, amateur or otherwise, as can be fitted into the available time, or to the affordable budget.
The author, with five friends, was able to plan and undertake such a trip, and with the contacts made over many years by the author, some wonderful, indeed fantastic, days were experienced. Both amateur, amateur related and mainstream sightseeing activities were part of the trip, which lasted for about a month.
The read will make you quite envious, and it is a read that I recommend you not miss.
A 50 W transmitter for 137 kHz
Author: Drew Diamond VK3XU
When Drew first developed this article, there was a likelihood that Australian amateurs would shortly gain access to this LF band, and so this offering describes, in Drew’s normal meticulous detail, how to gain a presence on the band by building your own 50 watt transmitter, that would also give excellent all round performance. (Note that Australian amateurs did, in fact, gain this band access).
Experience in building similar equipment, and some general knowledge of electronic theory, is necessary to build this transmitter. Additionally, a deal of common sense, significant patience and some self discipline, and a suitable work bench, will certainly make the task of achieving a suitable outcome very much easier – but if you do bring those skills to the exercise, and follow Drew’s recommendations and/or observations closely you will almost certainly end up with a piece of equipment that will allow you to operate on the band that is at the forefront of amateur experimentation in the coming period.
As always, a well written, concise article on a subject currently at the cutting edge of amateur experimentation around the world.
Simple wideband Yagis for 2 m and 70 cm
Author: Paul McMahon VK3DIP
If you are thinking of building your own 5-element Yagi antenna for the 2-metre or 70 cm band, turn to the very thorough article by Paul McMahon VK3DIP on page 10. Paul takes you through the design, construction and testing stages, based on a well-proven software package of his own. It is not easy to get a Yagi with constant gain across the whole amateur band, let alone constant feed-point impedance. But it can be done with know-how, persistence and a little compromise – just follow the procedures set out here and see the confirmation plots. Construction details are also well considered and documented, with plenty of practical advice from someone who has been there and done that.
The text in Figure 10 of the article did not reproduce adequately, so that figure is available below for download.
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Page Last Updated: Thursday 4 September 2008 at 12:9 hours
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