Receiving and tracking radiosondes
Weather services launch radiosondes on balloons every day. The sondes transmit position and readings in the 400.15 to 406 MHz range and can be received with a simple SDR. Signal-Pirat explains the tools and process and calculates how far a sonde at high altitude can be heard.
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What the page does
- Frequency range of meteorological aids: 400.15–406 MHz
- radiosonde_auto_rx scans the range with an RTL-SDR and decodes the sondes
- SondeHub shows reported sondes on a map; telemetry under CC BY-SA 2.0
- Radio horizon and level depending on sonde altitude
- Notes on landed sondes
Background
The radio horizon rather than the level usually limits reception: a sonde at 15 kilometres altitude is visible over several hundred kilometres from an antenna ten metres high. After landing reception stops once the sonde disappears behind terrain. According to SondeHub, readings received by amateurs are uncalibrated. A landed sonde usually carries a note from its operator; follow it and do not enter private land without permission.
In practice
How it works: enter frequency, transmit power and sonde altitude as well as height, gain and cable loss of your own antenna. The calculator shows radio horizon, level and margin at the horizon.
Frequently asked questions
Is receiving radiosondes allowed?
Reception is possible with standard receivers; the sonde transmits unencrypted. Transmitting on these frequencies is not allowed.
What hardware do I need?
An RTL-SDR receiver, an antenna for 400 MHz and a computer running radiosonde_auto_rx.