I just installed a new GNC-255. I did a radio check today from the ground, with other aircraft nearby in the air. When i activate the PTT, I hear static through the intercom (more than i noticed with my old ICOM). The other aircraft said they received my 5 by 5, and they said they did not hear any static over the radio. I heard their transmissions clearly as well. So I'm wondering why i get static on the intercom when i activate the PTT. Any ideas?