What is a real FM antenna? The best will be mounted outdoors on a roof with a rotor. Not so common anymore.
I've tried various fancy indoor antennas over the years, even been obsessed to pull in weaker more distant stations from time to time, and indoors always go back to a simple dipole or maybe rabbit ears. Only so much is possible even with amplification indoors. A strong noise free signal with little or no multipath is the key. Mounting antenna higher and outdoors will always deliver the best results. Attics are usually better than lower levels as well.
I've tried various fancy indoor antennas over the years, even been obsessed to pull in weaker more distant stations from time to time, and indoors always go back to a simple dipole or maybe rabbit ears. Only so much is possible even with amplification indoors. A strong noise free signal with little or no multipath is the key. Mounting antenna higher and outdoors will always deliver the best results. Attics are usually better than lower levels as well.