If you wanted a radio station at 99.5 FM, you had to ensure there wasn’t one at 99.7 already, or the interference would make yours incomprehensible. The same principle applied to other forms of radio communication. The more information that was packed into a given slice of spectrum, the less room there was for error created by muddled signals bouncing off buildings and interfering with each other as they careened through airspace toward a radio receiver.
