From my understanding, there are three SDFs:
- The SDF-1 which was the major focus of the first season.
- The SDF-3 which is the flagship of the Robotech Expeditionary Force (REF), where Rick Hunter is.
- The SDF-2 I wasn't too sure about, as at first I thought it was a separate ship built, but it was apparently destroyed with the SDF-1 in the final episode of the first season. (Not entirely sure if it's a separate ship or the repaired SDF-1.)
However, in Episode 78 ("Ghost Town"), the communications from the REF were coming from the SDF-4, so I'm wondering: How many SDF-#'s are there, and are they all the same as the SDF-1 (minus the aircraft carriers which were just a patch job)?