Live tracking
Update, Day 5, 21-Dec-2017
Photos of the launch
Transmitter photos

BB02 uses callsign ZL1RS and telemetry channel 02, and was launched on 17-Dec-2017 at 1745Z.

Further details, please see below!

Live tracking

Update, Day 5, 21-Dec-2017

BB02 is having a great flight! It sneaked through a gap in the weather and has clear skies ahead to South America! 

Photos of the launch

Transmitter photos

The tracker transmitter uses modified QRP-Labs U3S firmware running on an ATmega328 with a 16 MHz clock and a 3.3V supply (so working of spec). This time even more was cut off the QRP-Labs synthesizer kit to reduce weight! This synth board uses a very cheap TCXO from China. A BS-170 FET "power amp" has been added to provide 40mW output rather than the 10mW from the synth board alone, but the power level encoded into the WSPR transmissions is still 10dBm because the PA was added after the programming was done. The power supply is the same with four 52mm x 19mm solar cells producing around 2.4V in bright sun to supply the 3.3V boost regulator. The GPS is mounted upside down in 'dead bug style' where the Arduino's voltage regulator components were. The antenna is a 20m dipole made from 0.15mm copper wire going up to the balloon, and 0.1mm wire dangling below. The TX weighs 4.4 grams and the whole payload with solar cells and antenna weighs about 8.5 grams. A single 'party' balloon is inflated with just enough Hydrogen to give about 4 grams of 'free lift'.

The transmitter is sending WSPR and JT9 on the 20m band in a 10 minute cycle starting on the 4th minute (Frame Start = 10 04). The JT9 transmissions have been changed to provide more altitude information which is useful when the balloon starts dropping:

minute 04 & 05 - standard WSPR
minute 06 & 07 - encoded WSPR ('channel 0x2')
minute 08 - JT9 message #CS #M6
minute 09 - JT9 message #A0 #A3 #AT
minute 10 - JT9 message #GS #AT
minute 11 - JT9 message #A0 #A3 #AT
minute 12 - JT9 message #GS #AT
minute 13 - calibration (Cal Time = 10 10)
minute 14 - repeat ...

The JT9 message #A0 is the temperature A-D value and will probably be in the range 140 to 260 (approx. -5 to +34C)
The JT9 message #A3 is the solar cell A-D value and will probably be in the range 620 to 750 (approx 2.00 to 2.42V but displayed as 3.03 to 3.66V, see explanation below)
The JT9 message #GS is the ground speed value which will show as 3 characters
The JT9 message #AT is the altitude in meters above sea level.

Typical decodes as seen with WSJT-X and a receiver tuned to the 20m band WSPR 'dial frequency' of 14.0956 MHz (the JT9 signal can be found about 100 Hz above the WSPR signal) ...


0244   -3   0.5   14.097173    0   ZL1RS         RF64     10     74
0246   -3   1.5   14.097173    0   0V2SSW        QG79     47   2458


0248   -8  1.2  1669 @ ZL1RS RF64VS
0249 -10 1.5 1669 @ 247 762 370.6
0250 -9 1.3 1668 @ 0.00 370.6
0251 -10 1.5 1668 @ 247 760 370.6
0252 -10 1.4 1668 @ 0.00 370.6

As well as the map on this page, there is tracking at https://tracker.habhub.org/#!mt=roadmap&mz=3&qm=1_day&mc=-10,-130&f=BB02 and on APRS as ZL1RS-11 (thanks SM3ULC). The 'battery' voltage shown on Habhub is an indication of the solar array output, but needs scaling down by a factor of 1.51515 due to a 3.3V A-D reference used in my configuration instead of 5V. The 'temperature' reading seems a few degrees high, possibly for the same reason, or maybe that is the real temperature on the PCB next to the processor? The numbers for 'GPS lock' and 'satellite' should both read 1, meaning GPS lock = OK, and the number of satellites in the fix is 8 or more. If either reading is 0 this means the GPS is 'in trouble' and the balloon's position and altitude should not be relied on.