An Update: I've been hearing this intruder on 14002 over the past 8 hours or so, from 0528 (when the RTTY was strong, about S4 out of 5) to just now, 1210 UTC (5:10 a.m. local, Pacific time). The signal dipped into the static, just barely legible, around 0935 UTC.
It's been pretty consistent as RTTY though (or related FSK).
I've also heard a different RTTY signal at 14009 kHz, several times during the past several evenings. Earlier this a.m. (July 31) I heard the RTTY on 14009 at 0523, after which it put out a peep noise and then stopped. This also happened the a.m. of July 30th at 0530 UTC, and on July 26th UTC the 14009 RTTY was fairly strong, S4 out of 5, and it sped up its bit rate and then ended with a peep noise at 0525 UTC (10:25 p.m. local Pacific).
I'm not aware of all the amateur band plans world wide, but continuous RTTY doesn't seem to fit any amateur transmission procedures, and RTTY in the US is only slotted in above the CW band for the most part.
So I've got two mysteries, one on 14002 and the other one on 14009, which look like intruders. I'm still guessing Asia, due to the fadeout characteristics on 20M after 1 a.m. or so local time.
Receivers used have been DX-394, Tecsun PL-330, DX-398, all working off the same indoor, 25 ft second story wire. I'm in Western WA state.
Any ideas out there?