I wired up one of my D104 mics to my Icom-718 and I was surprised to see that it works WITHOUT a battery! How can that be? Also it performs well on SSB but on AM I can hear a squeal coming from inside the radio when keyed even if the mic element is removed from the mic base. I hooked a battery up and it changes nothing. Anyone know why there is a problem on AM with the mic base and how to correct it. Thanks in advance!