HM01 is a Cuban number station operated by the DGI.

Transmission format:

The messages transmitted by HM01 are computer files with 8-digit names and either .TXT, .F1C, or .F1G as the file extension. The files consist of unidentified binary data. The 5-digit headers consist of the last 4 digits of the file name, followed by a single digit age counter.

OFDM portions consist of a HamDRM data transmission. HamDRM is a DRM-based protocol used mainly in amateur radio for files and voice transfer. HM01 only uses the data transmission mode to send the files above, which can be retrieved using programs such as Easypal or WinDRM.

Scheduling

HM01 broadcasts the same set of six messages on all schedules, starting at 16:00 UTC, and concluding at 10:00 UTC the following day. Each one hour schedule of HM01 consists of two airings, on the hour and at the half hour, with a period of silence in between.

HM01 rotates its messages on a daily basis. When a message is new on the given slot, its counter (the last digit of the header) is set to 1. On the second day, the counter is still set to 1. From the third day onwards, the counter is incremented by one with each day. The day after the counter reaches 8, the message is replaced.

Operation quirks

HM01 shares transmission centers with the Cuban international broadcaster Radio Havana Cuba. It is not uncommon for RHC to be unintentionally broadcast on HM01's frequencies, and vice versa.

The audio for HM01 is provided by a computer running Windows XP, the sound effects of which are occasionally heard before transmissions.

History

HM01 was first heard on November 17, 2012, initially on some of the V02a and M08a schedules that had existed at the time. The current HM01 schedule was developed starting in December 2012, and has not been changed since early 2015.

From November 1, 2018 until January 10, 2021, HM01 updated its messages sporadically: the files were repeated day after day with unchanged counters for prolonged periods of time, usually for a few months each.

Up until mid-2021, HM01 used RDFT for the digital portions of the broadcast. RDFT (short for Redundant Digital File Transfer) is an off-the-shelf open source system, initially intended for amateur radio use. The DGI used DIGTRX to transmit and receive it. In the first transmissions using HamDRM in June 2021, the files sent carried an additional timestamp in the filename with a YYMMDDHHMMSS format, followed by "-" and the usual filename. The timestamp is believed to be the encryption date of the file.

From September 28 to October 5, 2022, HM01 remained off the air due to an island-wide electrical blackout in Cuba caused by Hurricane Ian. It was also offline from June 27 to August 22, 2023 for unknown reasons.

Location:  Google Maps