Sunday, 28 September 2014

The New Tracking Solution

The idea to track the balloon with the help of an antenna throughout the flight was there, but the knowledge and the experience with this field were not. Thus once more, I turned my attention to Google search looking for existing transmitter solutions and to physics textbook for the theoretical background. Not knowing what terms to look for, my search took a detour to tracking wildlife only to return back to finally finding a couple of websites describing tracking devices right for high altitude balloons.
The specific parts often differ, but the overall concept usually looks like this. A microcontroller (often some model of Arduino), a GPS module (one of the Ublox modules for example) and a transmitter (like Radiometrix's NTX2). All of this put together and programmed properly is capable of transmitting its GPS position (plus whatever you want it to transmit) that you receive via an antenna connected to a radio. For the powering purposes, a few AA batteries are used with the capacity of about 10 hours (this figure relates to my specific solution).

This is how it may look all put together. Arduino Nano, Ublox NEO-6M, Radiometrix NTX2, 6 AA batteries.

But transmitting the balloon's position is only a half of the story. On the other side of the transmission, you need to be able to receive it somehow. For this, I had to build an antenna (in my case I chose a 9 element Yagi for 434MHz) and find a way to process the signal. Since I didn't want to invest too much in a regular radio, I returned to Google. Luckily, I stumbled upon something called SDR (more on that later).

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