The tracker devices are rougly the size of a handheld radio and can operate on a battery for one day. Their main parts are a GPS receiver, a VHF data transceiver with a microcontroller, a flash memory to store location data and a battery charging circuit.
So far there have been 3 revisions of the tracker design including a very early prototype with a slightly different design. The very first tracker was crafted as a course exercise in Aalto University, School of Electrical Engineering, course Electronics Workshop (Elektroniikkapaja). The first prototype was a success with good-enough performance, based on which the second revision was designed.
The second revision (PB, as we call it) was based on a 32-bit ARM µC compared to the AVR in the PA revision. The radio part was integrated in the µC (EFR32FG1P131F256GM) and therefore the BOM actually decreased from the first revision. However, the PB came with some limitations, such as no power switchs for peripherals, and was surpassed by the production model PC.
The PC revision was designed in great hurry, since the competition was close. The ultimate design was sent for manufacturing in the end of July, only 1,5 months before the competition. The revision was success, however, and we managed to prepare 50 trackers for operations just in time. Literally - the last changes were made only days before the competition.
A fun detail: the tracker is protected by an ammunition pouch with PALS straps intended for military operations. However, the cartridges are now replaced by GPS tracking. The pouches were readily available at reasonable prices and were surplus.