E11b refers to E11 messages sent in years 2003-2009, with group counts in the 30's, which began and ended with "77777 77777." Such messages were sent on a randomly chosen week once a month. These groups were dropped in March 2009, but the once a month message procedure was retained.

This format first began in Morse code as M03c in August 2000, and later, in August 2006, S11a was also given its own variant, S11b.