According to the MT mil-gov frequency list:
Strategic Communications Wing 1 SCW-1 Frequency Channel Matrix HF-SSB
6691 kHz USB - CA - Charlie Alpha
11187 kHz USB - CB - Charlie Bravo
17892 kHz USB - CC - Charlie Charlie
Unknown designators:
11267 kHz USB, 13240 kHz USB, 14615 kHz USB
Apparently CD, CE, CF, CG, CK and CL have been referenced on-air, but their frequencies have not been confirmed.