Using Meshtastic devices the past two days at work. Communicating down a 120' vertical shaft and then down a corridor at the bottom. Solid concrete everywhere.

Using T-Beam Supremes and a Heltec v3 (it has no issues on the shaft either).

Radio comms don't work unless we're standing at the top and bottom of the shaft. The mesh allows us to even slightly communicate around corners since Bluetooth will go ~50'.

Very awesome! Now just need a intrinsically safe (explosive atmospheres) version of something like the T-Echo for when working around gas.