If you noticed an unusual white balloon floating overhead on Sunday, not only did you witness ham radio history, you also have superhuman eyesight.
To celebrate its 20th anniversary, the Adelaide-based Amateur Radio Experimenters Group released a balloon carrying a transmitter capable of broadcasting FM radio signals and static images as far away as Melbourne.
The balloon was launched from Mount Barker High School at 10am and quickly floated high enough to take in views of Adelaide, the Fleurieu and Yorke peninsulas, and the curve of the Earth's atmosphere giving way to the blackness of space.
It reached a height of 36 kilometres and zig-zagged across the sky, carried by stratospheric winds, before bursting somewhere above Monteith and falling to earth in a paddock south of Wynarka.
Recovery teams followed signals from an APRS beacon to find the exact landing site of the transmitter, a white object about the size of a shoebox.
Group member Mark Jessop said his team was able to follow its descent closely enough to watch it land from a kilometre away and, after obtaining permission from the property owner, go and pick it up.
He said the flight, the 50th conducted by the radio group under the name Project Horus, was just one kind of experiment amateur radio operators were interested in.
"Amateur radio is all about self-learning and experimentation," he said.
"It covers people who want to chat with people around the world, people launching balloons like myself, people who bounce signals off the moon ... there's all sorts of sub-groups."
As an electrical engineer, creating a device capable of the feats described above was his preferred challenge.
"You can go and buy a balloon off the internet, fill it with helium and let it go, but if you can't track it you're really just letting go of a big party balloon," he said.
"Some people launch GoPros and see pictures of the curvature of the Earth; that's well and good, but we want to see it live.
"That's where amateur radio comes in: anyone can capture these pictures, look at what's going on through the flight and track the flight as well."
The group achieved its aim with this flight, he said: its transmissions were picked up by an operator about 50 kilometres east of Melbourne.
- More information: Visit www.areg.org.au or search for #horus50 on social media.