[NoiseBert69]

> GPS is also unreliable in Ukraine, especially near the front line.

There are GPS antennas that physically can block out signals that are not coming from the sky with a huge amount of decibels. Maybe Aliexpress has some of them in stock? This was heavily ITAR-ed but this ban was lifted recently.

Other option: try to sync against the DCF77 signal from Germany. Not only the beep-beep-beep time signal but also the integrated phase modulation. Jamming VLF is difficult. 77KHz is in the range of ADCs.

Then make a voter: if GPS/GLONASS/Galileo/Beidou is available prefer them, if not fall-back to DCF77. If this fails: free-running.

[aftbit]

Cell phones are kinda nice because they're hard to ITAR. Anyone can buy them. Old and crappy ones are generally still good enough for this kind of micro model. They come with their own batteries to hold-over between power loss or overnight. They also come with their own sensors, radios, and compute already integrated. Basically, you can just write software and ignore the hardware side entirely.

Remember, this isn't planned to be a long term solution, or to provide the highest quality available, or to be the cheapest or most efficient solution. It's intended to allow Ukraine to quickly plug sensor gaps in the lines and to scale easily.