Michael, ZS1MJT, Regional Director for HAMNET Western Cape, reports that HAMNET Western Cape was requested to assist with communications on and around Table Mountain on 19 September 2026, by the Cape Province Mountain Club and the Kirstenbosch Rotary Group.
The aim of the event was to introduce scholars to hiking and the outdoors. HAMNET’s task was to provide radio communications from various control points back to a Joint Operations Centre (JOC).
While marshals could communicate with each other over specific, short-range areas, their communications were geographically limited by line-of-sight. This was where HAMNET was able to fill the gaps and provide communications between the various control points and the JOC.
HAMNET members and other marshals met at 05h00 on Saturday morning at the JOC, near the Kloofnek parking area. The HAMNET trailer was set up and, once parked and levelled, we were ready to operate.
A briefing was held to ensure that everyone understood what was expected of them. From 07h00, everyone deployed to their respective positions. Once all stations were in position, contact was established with the JOC and we waited for the participants to start and eventually arrive at our various positions.
The route started at the Kloofnek parking area, heading up Kloof Corner and then along the contour path on the Cape Town side of Table Mountain.
At the Platteklip intersection, the participants ascended Platteklip Gorge and proceeded to the dams on the back of the mountain. They then continued to the Cape Province Mountain Club hut, where they were provided with drinks and food before heading towards and down Kasteelpoort.
At the Pipe Track on the Camps Bay side, they proceeded back towards Kloofnek and the finish.
The scholars were in good spirits and showed a high level of enthusiasm, except during the couple of uphill sections! Temperatures on top of the mountain were around 22.5°C, with a very gentle breeze, making it ideal weather for outdoor activities.
A fun day was had by all, and HAMNET would like to thank the organisers for involving us. We also extend our congratulations to all the participants for completing the challenge.
Thank you also to all the marshals, officials, medical staff and Volunteer Wildfire Services for their contribution towards making this a successful day.
Finally, I would like to thank the HAMNET crew for giving up their time and sharing their expertise. They were Andre ZS1ATX, Torsten ZS1ABT, Ian ZS1BR, Andrew ZS1BAT, Shawn ZS1LED, Rassie ZS1YT and of course Michael ZS1MJT.
Thank you for the report, Michael.
In the ARRL newsletter of 24th September, it is noted that it’s been a half century since single sideband (SSB) supplanted amplitude modulation (AM) as the most popular voice mode on HF, due largely to its spectrum efficiency, occupying roughly half the bandwidth of an AM signal. Now, there’s a new digital voice mode from FreeDV called Radio Autoencoder, or RADE, that occupies half the bandwidth of an SSB signal and reportedly provides more natural-sounding speech.
According to Amateur Radio Digital Communications (ARDC), which funded research that advanced RADE’s development, “FreeDV RADE combines machine learning with classical digital signal processing (DSP) and can operate at signal-to-noise ratios (SNRs) as low as -2 dB. Its design also addresses spectrum use, speech quality, and power efficiency, all important considerations for voice communications over HF.”
Most significantly, ARDC reports that manufacturers are beginning to integrate the mode directly into their radios, starting with a module that can be downloaded and installed on certain FlexRadio models. Users of other transceivers may run the mode through computers connected to their radios. More details are available from FreeDV and on the ARDC website.
Thanks to the ARRL for these paragraphs.
Phys.org is reporting this week on research done to plan the layout of the antennas to be used at the SKA-Low radio-telescope in Australia.
Gaby Clark reports that the telescope being built in Western Australia will operate across a wide frequency range, from 50 to 350 MHz, and will be the most sensitive telescope of its kind ever built. The completed instrument will link 512 stations spread across an area roughly 75 km wide. All the station’s antennas work together like a single large dish, so their arrangement directly shapes what the telescope can detect.
An earlier prototype station, AAVS2, arranged its antennas in a scattered, pseudo-random pattern to avoid unwanted signal artifacts. But antennas placed too close together can interfere with one another, a problem known as mutual coupling. This interference grows stronger below about 150 MHz, squarely within SKA-Low’s operating range.
To address this, researchers at the observatory proposed a new arrangement inspired by the spiral pattern seen in sunflower heads, known as the Vogel layout. Spacing the antennas this way reduces interference between neighbors while preserving the station’s collecting power. The SKA Observatory built a new prototype station, AAVS3, using this layout to test it under real-sky conditions.
Simulations run while AAVS3 was being built predicted a loss of sensitivity directly overhead at around 125 MHz. The team traced this to repeated antenna spacings, about 2.4 meters apart, throughout the sunflower pattern. Those spacings create interference patterns that reduce sensitivity. The older prototype, AAVS2, showed no such problem with its scattered layout.
Observations confirmed the prediction. When the galactic plane passed directly overhead, images clearly showed the same dip in sensitivity at 125 MHz. This confirmed that the problem was a built-in consequence of the antenna geometry, not a flaw in the equipment or method.
Because of the sensitivity loss at 125 MHz, engineers ruled out the original sunflower layout for the finished telescope. Further simulations led them to a modified version, called “Perturbed Vogel,” which keeps antennas spaced to avoid interference while removing the repeating pattern that caused the problem.
The AAVS3 results give SKA-Low’s teams practical guidance for building and calibrating the stations during construction. Combined with lessons from AAVS2, this work has directly shaped the observatory’s testing process and supported a key construction milestone, known as AA0.5, marking the first stations to come online.
South Africa’s SKA antenna system will apparently not have this problem, because we will rely on incoming focused beams striking dishes, being undisturbed by neighbouring dishes and of course operating in much higher frequency ranges, where mutual coupling will not occur.
This is Dave Reece ZS1DFR reporting for HAMNET in South Africa.