 |
On January 22, 2022, an automated tracking system for weather balloons, also called radiosondes, was commissioned at the Coti-Chiavari site. The set consists of a Raspberry 3, a USB RTL SDR, a 403 MHz band filter and an omnidirectional antenna. Everything was installed in a rack drawer in the main bay of the site. The first tests are encouraging, the receiver decodes the frames emitted by the radiosondes as soon as they are launched and until the loss of the signal which varies according to the direction taken by the balloon |
The software installed on the Raspberry is that developed by Mark Jessop VK5QI and is available here. The receiver is an RTL SDR USB key in front of which a 403 MHz band filter has been inserted in order to avoid disturbances by the various signals present on the site, in particular the UHF TK5ZCG relay. Despite the small size of the filter, the results are more than correct.
The balloon launch site is located at Ajaccio airport (header photo) and is carried out automatically from a room located on the Météo France site. Two launches take place every day at 12:00 and 00:00 UTC. The main frequency of the transmitter is 401.000 MHz, the secondary frequency which is used if the first launch has a problem is 401.60 MHz.
Real-time data is uploaded to the Sondehub tracker and is visible to everyone. Private direct access to configure and monitor system operation is available. In particular, it makes it possible to visualize the radioelectric spectrum received on the antenna.
 |
Screen copy of a radiosonde tracking to a distance up to 97 km and a altitude of 70m before landing. |
First recovery
The release of March 9, 2022 gave a trajectory prediction with a landing near the village of Petreto-Bicchisano. The recovery was simple, the probe having fallen towards the top of the village and there was only 300 m to be done partly on a track and 100 m in a chestnut grove. Unfortunately, 99% of balloons end up at sea... :-(
 |
 |
 |
An M10 probe can recover some material. It is possible to modify the frequency of the transmitter in order to use everything in the 70 cm band. (see link below)
Reference :
Received datas display Web page.
Github for the autorx software.
Radiosonde path predictions.
Site de F0GYS pour la modification de la sonde M10