The Edgartown Planning Board Tuesday unanimously approved a plan to place a cell antenna in an abandoned silo in Katama, despite some opposition from neighbors. At meetings over the last few months, Katama residents had opposed AT&T’s plan to place the antenna in an abandoned silo at the Farm Institute, citing perceived concerns about radiation affecting property values and the Farm Institute’s donations, sales of produce and meat, and summer camp program. Farm Institute representatives said if the tower posed a risk to visitors or livestock, they would not have let the project go forward.