HAM Radio and Astronomy

My humble radio shack, including an Icom IC-R75 receiver.

I've been getting more curious about space weather lately, and it led me down a rabbit hole I wasn't expecting: amateur radio. Specifically, a digital mode called FT8.

Here's the gist. Ham radio operators use FT8 to send tiny digital messages, basically just call signs and signal reports, across huge distances using really weak signals. To get from, say, Texas to Australia, those signals don't travel in a straight line. They bounce off the ionosphere, a charged layer way up in our atmosphere, skipping across it kind of like a stone skipping across a pond. Whether that bounce works, and how far the signal makes it, depends entirely on how charged that layer happens to be at that moment.

I've always been into radio communications, but what got me hooked on this is what happens next. Every time one of these contacts gets made, it gets logged to a public database that anyone can look at. With thousands of operators making contacts around the clock, you end up with a constantly updating, crowdsourced map of how the ionosphere is behaving across the whole planet. Scientists used to need a network of expensive ground stations to measure that. Now there's a global hobby doing it for free, just by people trying to talk to each other.

And that's where the astronomy connection clicked for me. The ionosphere isn't some independent thing, it's shaped almost entirely by the Sun. So everything the Sun does shows up there fast. A solar flare blasts out X-rays that supercharge the ionosphere for a few minutes, and ham operators see it immediately as their signals fade out or go weird, all from something that happened on the Sun eight minutes earlier. The 11-year solar cycle shows up too, as long stretches where certain frequencies just work better or worse. There's even a research project called HamSCI that's used ham radio data from the 2017, 2023, and 2024 eclipses to literally watch the ionosphere weaken as the Moon's shadow passes overhead, then bounce back once the sunlight returns.

It's a neat loop when you think about it: the Sun shapes the ionosphere, the ionosphere shapes how far a radio signal can travel, and a global network of hobbyists chasing weak signals for fun ends up mapping the whole process.

I actually got curious enough that I've started monitoring FT8 directly with my own shortwave radios, using the FT8TW app alongside PSK Reporter to see what I'm picking up and where it's coming from. It's been fun watching which stations show up on a given night and thinking about what that says about conditions overhead.

The PSK Reporter website view of some of my recent FT8 catches.

I even got Claude to help me build a little app to log my own FT8 detections, so I've got a running record I can look back on. I may throw this app up on Github for others to use, as other shortwave radio listeners have been curious about it, it seems.

Screenshots from the FT8 logging app I vibe-coded in Claude.

It's kind of amazing that a hobby built around saying hello to strangers has turned into an accidental solar observatory, and now I've got a front-row seat to it.