A supplemental antenna assembly is provided for use with an electronic device having an integral radio antenna, such as a wireless-enabled laptop computer, notebook computer, gaming device, personal digital assistant (PDA), or circuit card (e.g., a PCMCIA card) or other circuit assembly designed be used with such a device. The supplemental antenna assembly includes a parasitic element supported by a frame. The frame is configured to be attached to the housing of the portable device such that an inductive coupling is provided between the parasitic element and the integral radio antenna. The parasitic element may include, for example, an antenna and/or a coupling element, e.g., a coupling element configured to be connected to an external antenna.