NOTE: This firmware works with the all variants of RS41 radiosondes, with the new RSM414 too. More below.
Vaisala some time ago began launching new RS41 sondes, with new internal design. They can be recognized by a last digit of 4 of the PCB model (eg. RSM414, RSM424). This firmware is an approach for reusing them as amateur devices for many different purposes. It also brings support for older models.
These small electronic devices are used by weather instututes to perform atmospheric sounding and high altitude measurements, up to the stratosphere (HAB - high altitude balooning). After the flight, usually they are meaningless for the launch company, so they can be collected by people (verify this according to the certain launch site). This acvitivty is called radiosonde hunting
The most simple and costless way of collecting radiosondes is to track them on sites like radiosondy.info or SondeHub (previously HabHub).
Another, more advanced way is to hunt them with radio receivers. Most of them transmit on the EU 400-406 MHz radiosonde band, near an amateur 70cm band. You can do that by a simple direction finding with a directional (for example Yagi) antenna and a handheld receiver.
But, currently the best way is to utilize a Software-Defined Radio (SDR, for example an RTL-SDR v3 / v4, Nooelec SDR, RSP1 or HackRF) together with a 70cm band antenna (dipole should work for sondes in air as far as 100km, the best is a high gain Yagi, with this setup you could easily hear a radiosonde hundreds kilometers away) and a specialized software for a computer, laptop or a Raspberry Pi. On the internet you will find lots of tutorials for receiver setup, tracking and hunting of them.
Kind note: After each hunt, either successful or not, please change the radiosonde status on the previously mentioned trakcing sites. This will not only let many people save on fuel and patience, but also allow everyone to take a look on sounding statistics and other things. On the most simple site for tracking (SondeHub) you don't even need to create an account to change the sonde status, which only takes a minute.
It's an unpleasant feeling, when after driving dozens of kilometers in search for radiosonde you come across an empty field without any ballon traces.
For more details about HAB and sonde hunting, please look on google and social media, there is a ton of valuable content.
RSM421, RSM414, RSM424), including the new ones with the '4' at the end of the PCB model.A thorough, detailed project guide is available at the links below.
If you want to fully utilize all capabilities of this firmware, please, read the documentation in the following header order:
See: fw/FLASHING.md
See: fw/COMPILE.md
See: hw/README.md
v25 - powerSave mode, featuring automaticaly-adjustable TX power and transmission intervals, based on the altitude. Changed default values of the firmware.v24 - some improvements in the GPS Dynamic Model setting, support for both old and new sondes, simple VALSET & VALGET validation mechanism for the new sondes. The Airborne 1G mode is still experimental!v231 - fix issues of the previous release v2.3, thanks to (still) this issue #3. Changed OIF411 data interpretation according to the operation manual (raw data division).v23 - added experimental uBlox GPS Airborne 1G Dynamic Model selection via UART of the module, thanks to this issue #3v22 - support for OIF411 ozone sounding system (including decoding the ozone info and transmision to ground), XDATA port mode selection (disabled, debug UART, XDATA UART), easy method of changing the payload-ID in Horus v2 mode, height activated oscillator heaterv21 - added support for old RS41 models (RSM412)v20 - initial public release, releases before this were never publishedIncoming features:
v22 version, but due to some develpoment site issues this will probably be added ater on)The creator of this project isn't at all responsible for any kind of harm made by devices operated with these instructions. Follow your local law about radio transmissions and ballon flights. This device isn't a certified airplane. This firmware wasn't tested in HAB scenarios, yet. Cheers.