Development of a tracker for Amateur Radio balloon flights. This has been going on for some time primarily with AVR based chips, and we are now launching RP2040 based hardware with functional 20 meter WSPR capability. APRS transmission in the VHF band are in development and coming soon.

Our current test flight AG6NS-11 was launched Saturday morning from Hayward California. Live tracking (updates when it's in full sunlight):

https://aprs.fi/#!mt=roadmap&z=11&call=a%2FAG6NS-11&timerange=604800&tail=604800

Vital Details:

Detailed Details:

The RP2040 is a dual ARM Cortex-M0+ running at 133MHz but can slow down to save power. The two cores are partitioned so one core is devoted to operating the tracker while the other is free for other purposes, like student experiments.

The tracker core firmware is written in C and assembler. It will send GPS position report and other data over VHF/APRS and HF/WSPR. The other core runs MicroPython. An API will provide the MicroPython environment with balloon information: GPS status, location, etc. Only a small set of the RP2040 user GPIO is needed for the tracker and the remainder is available for MicroPython programs. That allows for communications with a wide variety of sensors and actuators.

The tracker is small and lightweight, and is aimed at pico/high altitude ballooning. They would well for other platforms like the San Diego Mount Carmel High School Amateur Radio Club's (MCHSARC) amateur radio amateur radio marine buoy marine buoy.

The tracker generates a signal by modulating the Si5351 rapidly. It can produce VHF APRS AFSK 1200 BPS RF directly as well as HF WSPR < 0.5 BPS RF. Other modes have been demonstrated with this technique, like SSTV, but the tracker will only support APRS and WSPR for initial release. Other modes like FT8, more, RTTY and voice are of interest for reporting data. Other modes are being explored for sending more detailed telemetry.