Have picked up this one on two or three occasions in the past month on 8.221MHz CW, transmission its continuous with a set format:
NRVVU NRVFS NRVAN NRVHA NRVVF etc
Maybe it's a recorded "loop" that just repeats itself. Maybe the "NRV" is the key? Not 24 hours but usually around 1700z to 1800z I come across it up to 539 report.
Frequency could vary 1KHz either side of 8.221MHz as the Tecsun is not reliable via the BFO on CW frequency reception...
Any help on this one?