One of the dean of military monitors, Jeff Haverlah, posted the following to the Milcom newsgroup yesterday morning.
1130z 03 Apr 13
There's something noteworthy on the HFGCS. The HFGCS system has been running many 30-character EAM strings since at least 0300z+/- and probably earlier, with all 30-character strings rebcst at the systems h+00/h+30 restoral windows. Currently OFFUTT is bcsting 30-character strings 4V75ZO; 4VDWVK; 4VY6Vv at 1100z; and, a single string (4V75ZO maybe) at 1130z. As with any string greater than 28-characters all strings are sent with the character count statement. Unusual.
Yes, this is very unusual Jeff. I have a HF receiver parked on a HF-GCS and it will be interesting to see if we hear any 6/20/28c EAMs, in addition to those 30c messages you monitored yesterday going forward from here.