Skyfarer Cloud

Tracking high altitude balloons with WSPR

I’ve always been fascinated with amateur high altitude balloons. I’ve always wanted to launch a balloon with a radio payload and see where it goes and what data it collects. But, never have I ever, launched a balloon or helped out with a launch.

Recently I checked on the current state of the art, and I was blown away! Amateur radio operators are flying solar powered WSPR transmitters on balloons that stay aloft for weeks at a time. They circumnavigate the globe multiple times. Several are out there now floating around the earth at about 12000m (40000ft)!

I was already operating a WSPR station from time to time, I’m fascinated that I can put 1 watt into a piece of wire in my attic, and see stations all over the world hear my signal. More on WSPR here at WSPRNet. So naturally, the challenge of picking up one of these balloons was too much to pass up.

WSPR balloons are transmitting a standard WSPR packet, which contains a 4 digit maidenhead grid location. This defines about a 11000 sq km (7000 sq mi) box where the balloon is located. But some balloons are transmitting a second WSPR packet that’s non-standard. It encodes an additonal 2 digits for the grid square, plus temperature and altitude in a single WSPR packet.

There’s a tracking site called habhub that’s a neat site where you can see these WSPR balloons, plus APRS and LORA balloons as well. But I was a bit disappointed in the frequency of updates on the WSPR balloons. I wanted to try querying the WSPR spots data and decode the packets myself. I found that Dave, SM3ULC, has written a python script doing this and put it up on Github: sm3ulc/hab-wspr. I cloned it and tinkered around with it, and decided to write a Ruby version based on his ideas. Thanks to him, the math formulas were already worked out for extracting the telemetry from the WSPR packets.

My version is up on Github and there’s more details there if you find this interesting: jeremyfsu/hab-wspr-telemetry-decoder

Right now, my Ruby script runs every few minutes, queries for WSPR spots that are balloons, decodes them, then formats APRS packets from the data. I don’t send the APRS packets into the APRS network, there are people who do this already for the balloons. I don’t see the need to feed the already engorged APRS network. Instead, I’m sending the APRS packets to a local APRSC server, then mapping them with Xastir. Xastir is taking screenshots every few minutes and dropping them here: home.jeremywalworth.com/aprs “That maps looks like it’s from 2003!” you say. Yes, I run Xastir with a basic setup. But yes, I would like to make an embedded Google Map on a page and plot the positions. Habhub and aprs.fi already do an outstanding job at this. However, I think it would be cool to see my data plotted on my own embedded Google Map without sending to the APRS network or Habhub. Stay tuned, maybe I’ll get around to doing this. ;-)

It’s my hope that a future balloon operator might find my Ruby script useful for transmitting their balloon packets into the APRS network.