UBSEDS8 was our second launch with a 36” Qualatex Balloon. After breifly appearing to enter a float at 9.3km, this flight continued to slowly ascend, eventually reaching 11.2km. This is possibly a record for the highest flight with a Qualatex balloon.


This envelope was pre-stretched slightly more than UBSEDS6, eventually reaching an internal pressure of 4.9kPa as measured on the Omron M2.


This flight enabled APRS tracking outside of countires that disallow airbourne APRS operation. However no packets were heard, possibly due to the output power being too low. More investiagion required.

The output voltage swing from the TCXO on this board seemed particularly low, and it would not drive the MCU input. The TCXO is normally used by the MCU for symbol timing and to measure the TCXO drift against GPS, but for this flight the MCU used its internal oscillator. The frequency of the internal oscillator is only specified to ±2.5% and this error in the symbol timing prevented Contestia from decoding except at high SNRs. RTTY appeared to be unaffected.

The tracker failed about 4 hours into the flight. This didn’t appear to be related to low temperatures.




  • Total distance traveled: 404.2km
  • Great circle distance: 401.7km
  • Maximum altitude: 11.2km
  • Countries passed through: gb fr



Thank you to all listeners who tracked this flight!

Callsign Telemetry Lines Received Longest Path
G8DHE gb 331 241.7km
G6GZH gb 201 384.5km
F5APQ fr 187 263.1km
0x17 gb 184 290.1km
G8FJG_v gb 167 285.4km
G1DYQ gb 157 234.1km
G8IMN gb 148 304.6km
G8KNN gb 143 355.7km
ON5LT be 108 261.9km
M1ARI gb 69 88.8km
ASTRA gb 68 273.8km
M0SBU gb 65 102.7km
G8ZBJ gb 23 267.8km
ULC_websdr gb 21 120.1km
DutchMillbt nl 19 349.8km
G8FJG_V gb 15 282.7km
swl fr 14 85.0km
G0WXI gb 12 278.6km
G8FJG_H gb 5 125.2km
chimpusmaximus gb 2 205.7km