HM01 stands for Hybrid Mode number 1. It's the first "numbers" broadcast known that uses both AM voice and digital file transfer modes close together in the same transmission. Like most strange things nowadays, it comes from Cuba.
The Spanish language "female" voice uses the same digital samples as the existing voice schedule (V02a), which is still on air. The digital uses the same differential phase shift keying mode (called RDFT) as the earlier SK01, which was so called because an early version used a type of binary phase shift keying called PSK31.
RDFT (Redundant Digital File Transfer) is a very old mode by digital radio standards, having been developed by hams sometime around 2001. It's no longer used much, if at all, except by HM01 and SK01. The other noteworthy feature of these transmissions is that the RDFT is indeed sent in plain amplitude modulation (AM) mode, with two sidebands. These, of course, are identical, except in polarization.
ENIGMA 2000, the people who maintain the Control List of these designators, already has a preliminary schedule for HM01. This editor has been checking its times and frequencies, and the schedule presented here is only what has been heard at this QTH in California. Times are UTC, frequencies are kHz.
0500: 5855 has been heard Sunday and Monday, and may be a daily sked. 6165 was heard one Sunday.
0600: 10345 weekdays except (maybe) Thursday. 5800 Saturday, 6165 or 10345 Sunday.
0700: 9330 MWF and Sun. An unknown frequency in the 13 MHz range Saturday.
(Other skeds have been logged by others at 0800, 0900, and 1000 UTC. These have not been verified here.)
2100: 11635 MW and Sun. 16180 TThSat. Friday still not found.
2200: 10715 (MWFSun) alternates with 17480 (TThSat).
2300: 11530 (MWFSun) alternates with 17540 (TTHSat).
A lot more details about this weird new mode appear in the Monitoring Times Utility World column.
