开云体育

Hi Paul

In 2015 Dave VE3KCL contacted me with the idea of flying a streamlined U3S transmitter on a Pico balloon. Unlike conventional HAB flights which use Latex material that expands as it goes higher and higher, eventually bursting - picoballoons use inextensbible plastic (mylar film) balloons which reach an equilibrium altitude and can stay there for weeks or months or more, achieving very long distance round-the-world flights. Long distance communication is required.?

Within a few months I developed a telemetry-over-WSPR system and began development of what eventually became the U4B tracker . It sends a standard first WSPR transmission which conveys the 4-character Maidenhead grid. And a second WSPR transmission in which the bits are repurposes to carry 5th and 5th Maidenhead grid subsquare characters, altitude, ground speed, battery voltage, temperature and GPS status. To differentiate the telemetry WSPR transmission from other "normal" WSPR users, I use the callsign prefix 0, 1 or Q since there are never allocated by the ICU. The third character is a number 0-9 permitting 30 telemetry channels for various balloon users. Later the system was extended by x5 based on transmission times in a 10-minute slot, and transmission frequency (one of four 40Hz wide sub-subbands) - making a total of 600 channels.?

This WSPR balloon tracking telemetry system has been very successful and is implemented not just on U4B but on other (3rd party) tracker designs too, sometimes with some variations. WSPR is ideal for this due to the very high SNR, long communications range on HF, and global monitoring station coverage. You can read some details here? - some of this was modified slightly but the main concepts are illustrated well.

73 Hans G0UPL