We’ve reported on “space” balloons before. Heck, some of us have even launched a few. Usually they go way up in the air, take some cool pictures, and land within driving (and retrieving) distance the same afternoon. You get often amazing photos and bragging rights that you took them for the low, low price of a really big helium balloon and a fill.
But what if you shrunk everything down? Over the last few years, [Andy, VK3YT] has been launching ever smaller and lighter balloons with very low power ham radio payloads. So no camera and no photos, but the payback is that he’s launching payloads that weigh around thirteen grams complete with GPS, radio, solar cell, and batteries. They can stay up for weeks and go really far. We’d love to see some construction details beyond the minimalistic “Solar powered party balloon, 25mW TX”. But that about sums it up.
Did we mention that this “party balloon” started off in Australia, visited Africa, crossed over Australia again, visited Africa a second time, did a heart-shaped loop just outside Jakarta, and landed in Australia?
The payloads send very slow (QRSS), very low power (QRP) radio signals on a couple channels and using two different encoding schemes (WSPR and JT9) to maximize the chances of someone on the ground picking them up. The choice of the relatively low-frequency 20m and 30m bands helps a lot with long-distance signal propagation at low wattage levels.
To conserve power, the beacon only broadcasts a few times per hour unless the battery is fully charged. Receiving stations use software-defined-radio techniques to tease the low, slow signal out from the noise. And when anyone receives the signal, they can upload the telemetry data to habhub, a high-altitude balloon tracking network, to figure out where it’s from and where it’s going.
Twice around the world is incredible. But note that it’s [Andy]’s 46th such balloon. His first pico-balloon (PS-2, ironically) only stayed up for fifteen hours and made it under 800km away. Practice makes perfect?
We’ve written up WSPR on a Raspberry Pi (code and hardware) if you’re interested in getting started on WSPR on the cheap.
Thanks to [Bill Meara] of Soldersmoke for the tip.