An electronic device may be provided with wireless circuitry and control circuitry. The wireless circuitry may include multiple antennas and transceiver circuitry. An antenna in the electronic device may have an inverted-F antenna resonating element formed from portions of a peripheral conductive electronic device housing structure and may have an antenna ground that is separated from the antenna resonating element by a gap. A split return path may bridge the gap. The split return path may be coupled between a first point on the inverted-F antenna resonating element arm and second and third points on the antenna ground. The split return path may include a first inductor coupled between the first and second points and a second inductor coupled between the first and third points. The first and second inductors may be adjustable.