On real ham radios, you hold down a key to speak. Whenever someone spoke in the movie, they held down no keys, and just talked when they needed to. In reality, that's practically impossible because on real ham radios, you cannot talk onto of each other. So, when one person is talking, you can't talk on top, or if one person is keyed up, you can't talk on top still. So if that's the case, then how could the other one start talking if the other guy never UN-keyed up?