An intermod suppression panel consists of an isolator and a second harmonic filter. An isolator allows RF to pass in only one direction and the second harmonic filter reduces second harmonic signal produced by the isolator. Together they reduce intermodulation by suppressing signals received by the transmitting antenna. They also prevent any reflected power to be reflected to a load rather your power amplifier, which could cause significant damage to your amplifier. Reflected power can be caused by high VSWR, an open circuit, shorted antenna or from co-located transmitters at the site. Intermod Suppression Panels are a great way to clean up interference at a congested site, when a combining system is not feasible.