I want to build a receiver that constantly sweeps the United States FM broadcast frequencies between 87.8 MHz to 108.0 MHz.
However, I want to filter out any frequency that has a radio station broadcasting on it.
Is there a way to dynamically detect a frequency with a broadcast on it and not pass it to the output circuit that has a speaker?
In operation: 1) the circuit receives the first frequency in the standard U.S. radio range. 2) if the frequency has a broadcast on it, ignore it, otherwise send it to the output speaker. 3) If no more frequencies in range, go back to 1), otherwise receive the next frequency in range and go back to 2).
I want to receive only those channels without a broadcast on them, sort of like the opposite of a squelch circuit.
I am a beginning electronics enthusiast and this is an experimental application to prove a concept. I'm asking for help because I haven't the slightest idea whether it would work and if it could, how to go about building such a thing.