High altitude balloon tracker research

[Ryan]

I ordered the APRS tracker I intend to send up with the balloon and it was delivered... to some else... in Saint Louis. So they'll have to send me another one. 

In the mean time I've been looking at what other people have done for their APRS trackers and have come across a few interesting writeups. The intention here is to get a little bit of knowledge here and there of what worked, what didn't work, and what we can afford to do. 

http://surlee.com/forum/topic/balloons-in-space-nearly/ These guys had a very interesting antenna design but I don't think we can afford that much weight for the balloon size we have. There is some good information here however about how they recovered it and last gps position vs actual position. 

http://wotzup.com/2013/09/uplift-1-aprs-tracking-archives/ These guys have an interesting tracker that appears to integrate the antenna into the tracker board. I'm not sure how wise it is to have the radiating elements that close to the microcontroller though. 

http://k3jle.com/ I like the antenna they designed here.  I found this lightweight dipole antenna for $40 (bottom of the page) but I think we could make something similar for much less.

From the looks of it our antenna for the previous launch was insufficient and oriented in the wrong direction. I did recently acquire an antenna analyzer so we can test any antenna we make and tune it precisely to the frequency we use for APRS in the us (144.390mhz FM)

As far as ground station tracking I plan on using the same kind of tracker that we'll be sending up with the balloon either tethered to my android phone running APRSdroid (which requires a ham radio license) or to my laptop running Xastir (which does not require a license unless you hook it up to a radio capable of transmitting.) David has a handheld radio that is capable of decoding the packets as well. 

For anyone without a ham radio license I found some linux software called GQRX that can decode the APRS data packets using a ~$20 USB SDR commonly referred to as RTLSDR. http://www.george-smart.co.uk/wiki/APRS_with_the_FUNcube_Dongle  The instructions are for the funcube dongle but they are essentially the same thing. 

I encourage anyone who would like to be part of the chase team at the next launch to find a way for them to decode the APRS telemetry data. We can not rely on the cellular data network for access to online tracking. The more people we have actively picking up the packets when we chase our balloon the better chance we have of at least one of us decoding the last position of the balloon directly. 

[Ryan Raney]

Someone linked me to this page from the UK high altitude balloon... club... or something. 

https://ukhas.org.uk/frontpage:guides

They use a different frequency over there, 433mhz instead of 144, so their antennas can be physically smaller. I think we could pull of this design in particular though if we made it the bottom-most payload on the line https://ukhas.org.uk/guides:payload_antenna