An electronic device may include a conductive housing and an antenna. The antenna may include an arm formed from a first segment of the housing. A gap may separate the first segment from a second segment. Respective first and second slots may separate an antenna ground from the first and second segments. The antenna may have a first positive antenna feed terminal on the first segment and a second positive antenna feed terminal on the second segment. A transmission line may include a signal conductor having a first branch coupled to the first positive antenna feed terminal and a second branch coupled to the second positive antenna feed terminal. A switch may be interposed on the second branch for switching the antenna between a first mode in which the second slot is directly fed and a second mode in which the second segment is indirectly fed by the first segment.