To test UKHASnet network in the air on a balloon, to be launched on a latex balloon and act as a repeater for ground stations. To test range and whether it is possible to uplink data to the airborne node.
Using latest LPC810 code reporting onboard radio temperature, RSSI of the last packet received and baseline RSSI. Packets transmitted every 30 seconds, in between device is listening for incoming packets.
BALL1 was kindly launched by Steve Randall from Elsworth in Cambridgeshire. Launched with a backup 434 RTTY tracker on a Pawan 2000g Latex balloon with an ascent rate of approximately 2m/s and ascending to a maximum altitude of 32986m before descending by parachute. At the launch site was a UKHASnet gateway SR0 repeating at 50mW (old code) with a 1/4 wave antenna positioned on a car roof. The balloon was tracked on 434Mhz throughout the flight and landed in some trees in Suffolk where it was recovered.
A selection of packets during the flight
Reviewing the data it appears that the node worked well on the ground and worked during the early flight, it also worked on the late descent and was fully functioning when recovered. It managed to get 2 packets through during the middle (high altitude) part of the flight suggesting that it was running throughout (confirmed by Ron(G8FJG) who was able to tune in with an SDR to the signal). It would have been expected that the node would have performed better as it climbed due to improving line of sight however we did not see this.
Looking at the data received it appears that temperature may have had a big influence on the radio modules performance - we were only able to get packets where the onboard temperature was greater then -10C. If the radio module got too cold its crystal would drift which would affect both the frequency and the data rate. There would be a degree of flexibility to allow for a certain amount of drift but its unlikely that these cheap modules would have been tested to such an extreme.
Reviewing the RSSI graph as the node did not repeat any packets after 558m altitude both RSSI1 and RSSI2 during the flight measured noise floor. There is an obvious jump in the noise floor which occured straight after launch - this is most likely the fact that the node can 'see' more. The noise floor didn't change much during the flight itself which should lend itself to hopefully receiving packets in the future.