[superkuh]

Not only will the antennas have to be huge (or really inefficient like electrically small mag loops which throw away ~20dB of signal versus a resonant size antenna) but the legal limits on channel bandwidth and baud rate kick in.

You cannot legally do high rate networks on HF NVIS.

[maister]

It's true, this will certainly not be a high speed network as 2.7 kHz is the max allowed bandwidth (compared 500 kHz for LoRa). But it should be fast enough for transmitting text messages.

Antenna size is problematic, but NVIS does not require the antenna to be high up in the air. Also the polarisation must not be vertical, so throwing a simple wire dipole on the ground, might actually do the job. But we will see, it's an experiment.