Today, after an announcement on his blog , SV1NJX activated briefly a balloon tracker on 433.708 kHz using CW and FSK (ASCII 7N1, 50 baud, 450 Hz) at about 08:45 UTC.
The tracker signals were of good strength but with very poor stability, with pronounced chirp in CW and gradual frequency shift on FSK. I managed to decode a few packets using my Icom IC-7100 with DL-FLDIGI 3.21.5 and with an RTL-SDR receiver with SDR# and FLDIGI 4.1.06. AFC was absolutely necessary in order to keep decoding.
The actual balloon launch will take plane in mid-July 2021.