Abstract: An adjustable antenna assembly for a portable telephone includes a tubular base removably attached to a portable telephone, a socket securely received in the tubular base and having an outer periphery which is threaded in an upper end thereof, a coil received in the socket with a lower end thereof electrically connected to the telephone for receiving and transmitting wireless signal waves to the telephone, a cap having a closed upper end and an open lower end, the cap further having a threaded inner periphery and being mounted around the threaded upper end of the socket and thus being movable relative to the socket along a longitudinal direction of the coil upon rotational movement thereof, and a compressing member mounted between an upper end of the coil and the upper end of the cap such that a pitch of the coil is adjustable upon adjustment of relative longitudinal position between the cap and the socket.