Recently I'vs seen a good posting of people giving feedback to a RF communications engineer on what to be able to answer in the interview. I can't find it tonight, but I suggest searching the forum for 'interview'. You'll get well over 100 responses so you'll need to dig deeper. I suggest following the interesting ones with multiple replies as those had some prety good dialog going back and forth.
Maybe this will ring a bell for somebody else who knows the location of the post that I'm remembering to shorten your search...