Our high altitude weather balloon flights can be openly tracked and monitored in real time by anyone anywhere in the world using multiple methods. Our onboard balloon tracker system contains a high altitude GPS system which relays positioning back to ground stations via an onboard radio transmitter. Primarily, we use APRS (Automatic Packet Reporting System) as our balloon tracker which can be followed online at http://aprs.fi by searching for call sign KD2KPZ-11 or monitored by any amateur radio enthusiast on 144.390 MHz using standard APRS AX.25 protocol. In addition to APRS, our onboard tracking systems also broadcasts a secondary radio signal using RTTY (Radioteletype) as a backup HAB tracker. To decode the RTTY signal, we recommend using the software dl-fldigi. You can see additional details, below for details on how radio tracking high altitude balloons works for us.
Primarily, our ground team utilizes the online APRS website while tracking our flights via the onboard APRS transmitter, just because it’s the easiest to share and access on our mobile devices. However, we also receive and track the onboard radio transmissions ourselves too via the onboard RTTY transmitter, particularly when the flight is landing. Once our flight descends below approximately 2000 ft. (600m), the APRS signal reception can become unreliable so our chase car also monitors both the APRS and the RTTY radio transmissions so we can locate the final landing zone of the payload while the transmitter is broadcasting. Here’s our chase car setup for radio tracking our high altitude weather balloons.
Our primary chase vehicle is equipped with a 39-inch Nagoya antenna with a 5″ magnetic NMO mount. This antenna is routed into the vehicle and connected to a short MCX adapter cable which is then routed to a USB Radio Dongle connected to our field laptop. The laptop runs our Software Defined Radio (SDR) software, which is conveniently called SDR#, which receives the transmission from the antenna. This is enough to hear the raw audio from the transmission, but we need to take it a step further to “decode” the transmission so we use a Virtual Audio Cable to pipe the audio to another piece of software. For decoding APRS, we use direwolf to decode the transmission and set the direwolf “input” to the Virtual Audio Cable’s “output” audio. For decoding RTTY, we use dl-fldigi to decode the transmission.