September - October 2024
September-October 2024
 WIA Member Digital Edition Download
Editorial
Anniversaries
A short note on the VK1WIA broadcast of 4th August reminded listeners that the amateur radio satellite AMSAT OSCAR 7 (AO-7) would, in November, celebrate 50 years since it was launched. Why is this a “big deal”?
AO-7 is the oldest existing man-made space object still working!
That statement has gone unchallenged, so far. Not even the foremost space science and engineering nations – the United States and Russia, have claimed that. And they were “there” at the dawn of “the space age.”
Designed and built by radio amateurs for use by radio amateurs, AO-7 is still able to receive operators’ signals on one amateur band and re-transmit them on another, its primary intended purpose.
That bird set some early, important records for amateur radio involvement in space science and engineering. And is continuing that sterling tradition. AO-5 wasn’t the only amateur radio satellite having Australian involvement. Australian amateurs were also involved in AO-7. That’s an even bigger deal. Don’t miss our next issue.
There’s another 50th anniversary to celebrate, or perhaps it’d be better to say, commemorate. On Christmas Eve 1974, Cyclone Tracy swept across Darwin, devastating the city.
In the immediate aftermath, a small band of radio amateurs resident there played an important role in re-establishing communications links alongside the efforts of other individuals and services. Other amateurs at the end of those links also played important roles. We’re preparing a feature covering this landmark event, also for publication in the next issue.
A salutary lesson
Throughout the suburbs in cities and towns nation-wide, National Broadband Network (NBN) services are distributed to homes and other premises by the old, now re-purposed, hybrid-fibre-coax (HFC) network, as well as by the now-repurposed twisted-pair telephone network.
The coax portion of the HFC network is a 70 Ohm, coaxial cable system, having bidirectional amplifiers at intervals to maintain the signal levels. To service connection to homes and other premises, an in-line junction box provides a tap point for a light coax cable “drop” to the house. There, the modem that enables PC and TV connection terminates that coax line to the premises.
When a home or other premises are disconnected from the HFC-provided services, the drop cable is sometimes just cut and taken back to the street pole, where it is wound up and left on the roadside nature strip. Apparently, this sometimes happens when homes are demolished for repurposing the land.
Unterminated coax is an antenna, as RF impinging on the coax cable outer conductor induces a current that then flows into the internal portion of the line, conveying the passing RF into the network. Proper practice is to remove the coax at the junction box and attach a terminating connector.
An NBN service technician learned a salutary lesson, or two, when he went to investigate interference to the HFC services in a Melbourne neighbourhood recently, as our correspondent tells the tale in later pages.
In addition, those dangling, unterminated coaxes will also radiate signals from the HFC network, adding to the RF fog that now bathes our urban habitat.
Table Of Contents
General
 Incident with RFI to the NBN resolved successfully - Ashley Geelan VK3HAG
On the bands, far out at Farina - Glenn Alford VK3CAM
Historic QSL Bureau - Fred Swainston VK3DAC, VK4FE
Technical
Antenna matching unit for balanced feedpoint antennas - Donald Howarth VK6JDM
Command your Icom rig with this simple Arduino-based keyboard interface - Peter Elekessy VK2AN
Comprehensive, innovative test sets for processing homebrew transmitters - Part 3 - Lou Destafano VK3AQZ
A practical transverter for 241 – 250 GHz - Andrew Anderson VK3CV / WQ1S
A good joint might be hard to find - Jim Tregellas VK5JST
Experiments using digital modes to identify VHF auroral propagation types - Rex Moncur VK7MO, Brodie Churchill VK3MAP and Dr Andrew Kelekociuk
Page Last Updated: Tuesday, 24 Sep 2024 at 22:15 hours by Webmaster
|
