New pilot, need help! I bought a Vertex Standard handheld radio for use in my Aeronca Chief. Worked fine for a couple of days, but started to squeal ( feedback? ) when I push the PTT switch. I have a Lightspeed LT 20 and a Bose Quiet Comfort 15 headset, and an external PTT switch from Aircraft Spruce and it does the same on both. Bought an I-Com A-24 after I sent the Vertex off To get checked out and it does the same thing. Makes no difference with or without the intercom ( Sigtronics) in line. Dealer says there is nothing wrong with the Vertex radio, but has no suggestions as to what is wrong. Called I-Com, and the guy I talked to didn't have a clue, either.