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This is still a work in progress, but is functional in it's current state. I owe credit to David SM3ULC who wrote a python version of this here. I used some of the math that he worked out for decoding the telemetry. Also this spreadsheet was indispensible for checking the accuracy of my decoding logic. I'm not sure who gets credit for the spreadsheet, but I suspect it's the most prolific balloon guy, Dave, VE3KCL. This dude launches balloons that circle the earth multiple times, one is on it's 16th or 17th trip as I write this (Sept 24, 2021).

Here's the basic process:

  • First this queries a live WSPR spot database here.
  • Then looks for telemetry using the "Special WSPR Telemetry Protocol described here
  • Attempts to decode the telemetry. If a telemetry packet isn't found, it uses the coarse 4 digit maidenhead grid from the first spot for the next step, otherwise, uses the decoded 6 digit maidenhead for a finer position.
  • Constructs an APRS packet and sends it to an APRS port.

At home, I have Xastir and a local APRSC instance running, this feeds my local APRSC which Xastir is listening on, and plots the balloons on my Xastir map. I'm not sending anything to APRS-IS currently. As far as I understand, only designated people are actually sending WSPR HAB spots to APRS-IS so they're seen on APRS.FI.

Update: now uses REDIS

I've added support for REDIS. Now it will keep track of APRS packets sent and not send duplicates.

Things I still would like to do:

  • Build an embedded Google Map page that maps the balloons, and uses the above Redis to get periodic updates
  • Keep the last Grid value in REDIS. If, on the most recent update we only received a 4 digit grid, and it matched a previously received 6 digit grid, then send a new APRS packet but use the 6 digit grid position as long as it's still within the larger 4 digit grid.


High Altitude Balloon WSPR telemetry decoder







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