Some Naval planning chap decided to use the FOST complan for an exercise off Scotland - reasoning that the two fleets would not be in line of sight of each other...unfortunately he hadn't reckoned on an E-3 joining in on the FOST weekly war off Portland. Equally unfortunately, said planner had used the same callsigns to be used on the Hebrides fleet as those in use by FOST. Joining the Anti-Air Warfare Net caused a degree of confusion for the northern fleet as an unexpected AEW asset joined them on frequency, but they assumed that this was a staff inject and so off they went - unfortunately also using the same crypto set. Within a few minutes total confusion reigned as both fleets joined into the same L11 net with all sides claiming of comms jamming and so on. Eventually, the penny dropped as the E-3 took on the main data link duties and the ships positions were noted although they were running the same Data Link plan as well and ships positions began "jumping" between the Channel and Scotland. We eventually moved to an orbit further south to drop the northern fleet beyond line of sight (although the HF nets continued to cause trouble for the rest of the serial so we binned them). It was an interesting misrep sent back to Group, info Navy that night.