Thursday, September 13, 2007

Cuban DIGTRX Numbers 9/13/07

The Cuban numbers stations, always good for a surprise, are at it again.

On September 10, Tom Sevart heard a new digital mode (for them) on 17478 kHz USB at 1600 UTC, and again on 17436 kHz USB at 1700. This is an 8-tone modulation mode with distinctive beginning and ending signals. It was quickly identified by Tom and others as Redundant Digital File Transfer (RDFT), a mode with several submodes of varying transfer speeds. It's used by hams for transferring files, usually slow scan TV (SSTV) pictures. We've written about this before.

Today, September 13, Tom and I both heard transmissions at 1700 on 17436. They were in RDFT and another digital file transfer mode called HamDRM, an amateur version of the Digital Radio Mondial broadcast standard. The program in use identified itself as DIGTRX version 3.11, a free download available on all the usual ham radio sites.

The sending station ID in the DRM transmission was RAD01. The file being transferred was called nen12.txt. Its contents are a standard V02a/M08a three-message encrypted whatever, but without the formatting into 5-figure groups. We thank Tom for sharing his decode with the Internet.

It is interesting to speculate on whether RAD01 and nenxx.txt are internal names used in the Cuban numbers operation, or just special test names. Probably ultimately futile, but interesting.