Just want to throw my $.02 here as an AV professional - you should ALWAYS scan every day before use. You have no idea who is doing what in your vicinity. I work 3/4 shows a week in Chicago area and we get RF interference maybe 20% of the time when setting up and leaving mics at the same freq as last time.... for sennhieser, the RF meter on the receiver should be your best friend! The little bouncing bar graph on the left side of the display is RF. You do not want it to move when transmitter is of. Never.