Foundations of Amateur Radio
In the middle of the night when insomnia rears its head, there are occasions when an idea sprouts that is still with me the next day. I imagined a spinning globe that shows ionospheric propagation and allows you to navigate around the world and experiment. Think the ionospheric equivalent of windy.com in 3D.
To get to that point, I started off with the Australian Space Weather Forecasting Centre. I was on a roll when I discovered that under "HF Systems" it has a "Global HF" section with "Ionospheric Map", which, curiously enough, shows exactly what you'd expect.
What surprised me was that below the map is an animation viewer that allows you to see the last three days in half hour increments. Excitedly playing with this I found myself locked out and on the phone to the Bureau of Meteorology. I suspect that someone didn't tell the people who configured their content delivery network that users might be loading a gross of images from their website in short order, or two gross, if you also look at the "T-Index Map", like I did.
With no immediate solution on the horizon, I went on the hunt for other sources of maps and discovered the NASA/JPL-Caltech GUARDIAN project, described as near-real-time ionospheric monitoring software for natural hazards warning.
Their website has a limited archive of daily videos showing how the ionosphere changes, which was exciting until I discovered that my computer wanted to download each one, rather than play them in the browser, so making lemonade, I downloaded all of last month, thank you "curl", used my favourite video editing tool, "ffmpeg", to combine them, then uploaded the result to my VK6FLAB YouTube channel for our enjoyment.
What's fascinating to me is being able to see, for the first time, just how the ionosphere changes throughout the month. You can see where there's regular solar activity and where exceptions occur. I'll note that there's a few gaps, I suspect that the software behind the scenes at JPL had some outages, but what's there is what was available.
Now for the interesting stuff.
This data is not created by something monitoring in space at L1, or in orbit around Earth, it's created by ground stations scattered around the planet. GUARDIAN is based around the Global Navigation Satellite System or GNSS. The project, to give its full name, the GNSS Upper Atmospheric Real-time Disaster Information and Alert Network, uses the radio signals from the four navigation constellations, GPS, Galileo, BDS and GLONASS.
Name aside, the project has some really interesting goals; objective one, the result of which you can see in the video or on the website, is to allow users to explore ionospheric perturbations, in other words, you can see how the ionosphere changes over time.
This is achieved by some cool radio phenomena, specifically, two different GNSS carrier frequencies will show phase change as well as alter what's known as "pseudorange", the apparent distance between a satellite and a receiver, affected by among other things, the "Total Electron Content" or TEC along the signal path. What that means is that the satellite signal is directly and proportionally affected by what's happening in the ionosphere. As an aside, this phenomenon can impact your mobile phone navigation, more on that in a moment.
In other words, if you can measure how the radio signals from a navigation satellite change, you can calculate what the ionosphere is doing along a direct line between the transmitter and receiver, in response to natural and man-made events on Earth.
If that's not enough, remember, this is just the first objective, the second one is to automatically detect those changes, the third objective is to characterise potential natural hazards.
Lots of words to say that the aim is to detect events like geomagnetic storms, tsunamis, earthquakes, volcanic eruptions, thunderstorms, not to mention explosions and rocket launches.
You can explore some historic examples on the GUARDIAN website at JPL. You can also compare the current planetary geomagnetic index with what comes out of the GUARDIAN project.
At this point you might wonder what the ionosphere has to do with tsunamis? As it turns out, a whole range of natural and man-made hazards impact the ionosphere due to significant displacements of air at the surface, and the project used historic hazards and ionospheric data to link the two, and in July 2025, the magnitude 8.8 Kamchatka earthquake and associated tsunami was automatically detected 30 minutes before it reached the coast of Hawai'i.
If that doesn't hit you in the Wow spot, during my research I came across several projects that explore the use of mobile phone GPS receivers as sensors. There's billions of those, so potentially, planetary coverage. For comparison, in 2022 there were 80 Global Differential GPS ground stations powering GUARDIAN, today the network has over 200 sites.
Google Research published an article in 2024 using the same methodologies to measure the ionosphere using millions of mobile phone GPS receivers, effectively doubling coverage. Their article in Nature goes into detail which devices were used and how, essentially, using anonymised and privatised Android location data.
From an amateur radio perspective, it's interesting to note just how variable and dynamic the ionosphere is and what types of phenomena affect it. I also wonder if my PlutoSDR might be used to have a go, since we're talking about radio frequencies around 1.1 and 1.5 GHz.
All the more reason to get on-air and make some noise and excite the ionosphere and a receiver somewhere on Earth.
I'm Onno VK6FLAB
