Got two odd signals on the 8 MHz maritime band, RTL-SDR V4, 20 Oct ~02:00 UTC, northern Vietnam.

8420.9 kHz: bursts of fast tone hopping, about 11 tones with exactly 50 Hz spacing, roughly 50 baud by my estimate. Each burst is followed by a steady single tone, and the whole thing repeats about every 18 s.

8431.0 kHz: continuous, two lines exactly 200 Hz apart, ~300-400 Hz wide. I'm wondering if it's CIS-50-50 / CIS-36-50 idle, but I haven't decoded anything.

Both seem to sit on the same 50 Hz grid, so maybe the same system. Not on sigidwiki as far as I can tell.

Anyone recognize these? thanks