An electronic device, comprising: a housing having edges and a peripheral conductive member that runs around the edges of the housing; first and second antennas; radio-frequency transceiver circuitry having first and second ports; switching circuitry that is operable in a first mode in which the first antenna is coupled to the first port and the second antenna is coupled to the second port and that is operable in a second mode in which the first antenna is coupled to the second port and the second antenna is coupled to the first port, characterized in that: the first antenna is configured to transmit and receive radio-frequency signals in a plurality of cellular telephone communications bands during the first mode, and the second antenna is configured to function as a receive-only antenna and to receive radio-frequency signals in a subset of the plurality of cellular telephone communications bands during the first mode, wherein first and second gaps in the peripheral conductive member divide the peripheral conductive member into a segment that extends between the first and second gaps, and the segment of the peripheral conductive member forms part of an antenna resonating element of the first antenna; and a tunable matching circuit interposed between the second antenna and the switching circuitry. a housing having edges and a peripheral conductive member that runs around the edges of the housing; first and second antennas; radio-frequency transceiver circuitry having first and second ports; switching circuitry that is operable in a first mode in which the first antenna is coupled to the first port and the second antenna is coupled to the second port and that is operable in a second mode in which the first antenna is coupled to the second port and the second antenna is coupled to the first port, characterized in that: the first antenna is configured to transmit and receive radio-frequency signals in a plurality of cellular telephone communications bands during the first mode, and the second antenna is configured to function as a receive-only antenna and to receive radio-frequency signals in a subset of the plurality of cellular telephone communications bands during the first mode, wherein first and second gaps in the peripheral conductive member divide the peripheral conductive member into a segment that extends between the first and second gaps, and the segment of the peripheral conductive member forms part of an antenna resonating element of the first antenna; and a tunable matching circuit interposed between the second antenna and the switching circuitry. the first antenna is configured to transmit and receive radio-frequency signals in a plurality of cellular telephone communications bands during the first mode, and the second antenna is configured to function as a receive-only antenna and to receive radio-frequency signals in a subset of the plurality of cellular telephone communications bands during the first mode, wherein first and second gaps in the peripheral conductive member divide the peripheral conductive member into a segment that extends between the first and second gaps, and the segment of the peripheral conductive member forms part of an antenna resonating element of the first antenna; and a tunable matching circuit interposed between the second antenna and the switching circuitry.