track migratory birds with SDR and RASPi on VHF frequencies.
A new ICSSW.org project is just getting off the ground. The aim is to use the expertise of radio amateurs and interested parties to simplify and automate the observation of wild animals. In many areas of zoology and biology, wild animals are equipped with simple, small transmitters in order to better study their behavior. Migratory birds are particularly noteworthy here, as they cover long distances. However, similar tasks also arise with species that lead a very hidden life (wolves, bears, bats).
The transmitters
The transmitters come from specialist companies such as LOTEK and are sometimes only a few grams in weight, as they must not be a hindrance in relation to the animal's body weight. Therefore, there is not always room for GPS receivers or satellite uplinks. So-called "beeper tags", which only transmit carrier pulses, are used. They usually transmit around the 2 m band (specified frequency range for animal telemetry of 150.05-150.24 MHz), but there are also models on 70 cm.
The receiving station
An automatic receiving station consists of a Raspberry Pi with free software and one or more RTL sticks as SDR receivers and a directional antenna (Yagi). This allows several directions to be covered simultaneously.
The software scans the specified frequency range and detects the radio signals. These are entered into a table (database) and also located using the field strength on the individual antennas. Another option would be localization by evaluating the transit times if different locations are equipped with networked receivers. OM Werner Dreckmann DH4KAV and his team have already done a great deal of groundwork in this area and have successfully received bats (BAFF). The evaluation is carried out with the data analysis software "R".
What hardware is required:
- Raspberry Pi 3B, 3B+, 3A+ (or better)
- RTL USB dongle with chipset R820T, or R820T2 (E4000 works, but not recommended)
- 3-6 Element Yagi antenna https://www.aatis.de/content/praxisheft-27 Page 131
The software and detailed instructions are available for download at radio-tracking.eu.
- https://radio-tracking.eu/wp-content/uploads/2019/07/rteu_Tutorial_DH4KAV_V1.8.0.pdf
- https://radio-tracking.eu/software/download
You can find more information on how to get involved and other exciting projects at www.ICSSW.org, the platform for innovation and citizen science with wireless and space technologies.