I know how:
It says he showed video at 15fps
It says he used HAM on an A2000, so HAM6 it is.
It says the show was in NY, USA so probably used some NTSC image size
Then we do the math with little guessing:
Datarate 320x200x6bitx15fps= 704 KB/s rounded up
So, it is pretty doable, with, of course, the right storage media and its appropiate interface. You could even do it better!