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U3S

Live tracking
Photos of the launch
Transmitter

BB03 uses callsign ZL1RS and telemetry channel 02.

Further details, please see below!


Live tracking


Photos of the launch

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Transmitter

BB05 was launched at 21:15 UTC on 24 April 2018.

The tracker transmitter uses modified QRP-Labs U3S firmware running on an ATmega328 with a 16 MHz clock and a nominal 3.3V supply (so working out of spec). The board is a custom made PCB (thanks Mikael). This board uses a very cheap TCXO ($1) as the synth reference oscillator and a very cheap GPS module ($3), both from China. The Si5351a synthesiser is followed by a 2N7002 FET PA and LPF, the power output is 50mW. There are four 52 x 39mm solar cells powering the electronics via a 3V3 boost regulator. The antenna is a 20m dipole made from 5.26m of 0.15mm copper wire supported on 4 pound breaking strain "Dyneema" fishing line going up to the balloon, and 5.26m of 0.15mm wire dangling below the payload. The TX and solar cells weigh 14 grams, and the whole payload with antenna weighs about 16 grams. This flight uses a larger custom made balloon inflated with about 10 grams of 'free lift'. The expected float altitude is around 13,000m ASL.

The transmitter is sending WSPR and JT9 on the 20m band in a 10 minute cycle starting on the 4th minute (QRP-Labs U3S "Frame Start" parameter = 10 04).

minute 04 & 05 - standard WSPR frame and first part of the telemetry transmission
minute 06 & 07 - encoded WSPR frame and second part of the telemetry transmission ('channel 2')
minute 08 - JT9 identification message with QRP-Labs message hash tags #CS #M6
minute 09 - JT9 telemetry message #A0 #A3 #AT
minute 10 - JT9 telemetry message #GS #AT
minute 11 - JT9 telemetry message #A0 #A3 #AT
minute 12 - JT9 telemetry message #GS #AT
minute 13 - calibration (QRP-Labs Cal Time parameter = 10 10)
minute 14 - repeat ...

The JT9 message #CS is the callsign (ZL1RS)
The JT9 message #M6 is the 6 character Maidenhead locator as derived from the GPS module on the transmitter
The JT9 message #A0 is the temperature A-D value and will probably be in the range 090 to 220 (approx. -21 to +21C). A value of 155 = zero degrees C.
The JT9 message #A3 is supposed to be the solar voltage, but something broke and it sends "A17" every time ...
The JT9 message #GS is the ground speed value from the GPS
The JT9 message #AT is the altitude in meters above sea level from the GPS.Typical decodes of the balloon telemetry 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) ...

WSPR:
2334 6 0.0 14.097180 2 ZL1RS RF75 10 141
2336 6 0.1 14.097181 2 0R2DPN IE58 30 11506

JT9:
2338 3 -0.9 1667 @ ZL1RS RF75SO
2339 1 -0.9 1667 @ 173 A17 13133
2340 2 -0.9 1668 @ 119.32 13135.
2341 1 -0.9 1667 @ 175 A17 13129
2342 1 -0.9 1667 @ 118.78 13127.

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