There are first and second antennas proximally disposed and configured to resonate within respective first and second frequency bands, which may overlap. An impedance stabilization circuitry is coupled to ground. There is a selective coupler (for example, diplexer, directional coupler, switch) interfacing the second antenna selectively with the impedance stabilization circuitry and with radio circuitry. The selective coupler comprises a first port coupled to the second antenna, a second port coupled to the impedance stabilization circuitry, and a third port configured to couple with radio circuitry that is configured to operate in the second frequency band. The selective coupler provides a predetermined impedance to signals within the first frequency band and a low insertion loss to signals within the second frequency band, thus providing a stable impedance for the first antenna's view of the second antenna.