I am an aspiring science fiction writer. By training I'm a psychologist, so my knowledge of physics is somewhat limited. (I like understatement.) In the story I am currently writing, I have a military base surrounded by a force field, which I assume would be some sort of EM field. If I set up my commandos with a mobile EM emitter and have them set it to the same frequency as the base field, would they be able to pass through? If not, what could they do instead and still maintain secrecy?