Although the distance these balloons have travelled is quite remarkable, the interesting part is how [David] is tracking the balloons. Cell phones obviously won’t work over the Atlantic, and satellite transmitters are expensive, so he used a low-cost transmitter that was programmed to broadcast using a variety of Ham radio signals. The most effective seems to be WSPRnet (the Weak Signal Propagation Network), a system used by Hams to see how far low strength signals will go. This system relies on Hams leaving their receivers on and running software that uploads the received signals to a central server.
By cleverly encoding information such as height and position into this signal, he was able to turn this worldwide network into a tracking network that would report the balloon’s position pretty much anywhere on the globe. [David] is continuing to launch balloons: his latest went up on the 24th of September and travelled over 4300km (2600 miles) before the signal was lost over the Atlantic.
Don’t get us wrong, we love our Raspberry Pi. But if you’re merely running a Linux image without adding a hardware hack into the mix you’re missing out on part of the power for which the platform was developed. This project is a great example of how to embrace the Raspberry Pi’s ability to deliver both low-level hardware access, and solid embedded Linux performance. [Dan Ankers] and [Threeme3] have developed a program which turns the RPi in to a WSPR transmitter. The GitHub readme shares many of the details on how it was done. But you’ll also want to dig through the .c file to see how they’re making use of the GPIO header pins.
[William Meara] sent in the tip for this. He’s been featured on Hackaday previously for his work with WSPR (Weak Signal Propagation Report). It’s an amateur radio protocol which lets you communicate over very long distances using relatively weak transmitters. The trick is to use computing power to find the signal hidden in all the noise. Be warned that you do need a HAM license to try this out, but otherwise all you need to connect to the board is a low-pass filter and an antennae.
Host of the Soldersmoke podcast, [Bill Meara], contributed this guest post.
WSPR is a new communications protocol written by radio amateur and Nobel Prize winner [Joe Taylor]. Like the very slow QRSS system described in a previous post, WSPR (Weak Signal Propagation Reporter) trades speed for bandwidth and allows for the reception of signals that are far below the level of radio noise. WSPR takes “low and slow” communications several important steps ahead, featuring strong error correction, high reliability, and (and this is really fun part) the automatic uploading (via the net) of reception reports — [Taylor]’s WSPR web page constantly gathers reports and produces near real-time Google maps of showing who is hearing who. The WSPR mode is very hack-able: [Bill Meara] is running a 20 milliwatt homebrew transmitter from Rome, Italy that features an audio amplifier from a defunct computer speaker pictured below. This contraption recently crossed the Atlantic and was picked up by the Princeton, New Jersey receiving station of WSPR’s esteemed creator, [Joe Taylor]. Continue reading “WSPRing across the Atlantic”→