This extendable antenna is related to an extendable antenna for a portable radio transceiver. The antenna has a first antenna portion and a second antenna portion connected with a connecting portion of the first antenna portion. The first antenna has a loading coil which is enclosed in a top end cap. When the second antenna portion is retracted into a housing, the connecting portion is held by a holding member disposed in the top of the housing, and the connecting portion is ellectrically connected with the circuitry of the transceiver via the holding member. Furthermore, the electrical length of the loading coil is a quarter wavelength, while the physical length of the loading coil is much less than a quarter wavelength. Accordingly, even if the top end cap is only located out of the housing, the first antenna portion detects a radio frequency signal. Furthermore it is unnecessary for the radio transceiver to have an inner antenna and a rod antenna, and switching means for switching from the rod antenna to the inner antenna. And it is unnecessary for the housing to have space for the the inner antenna.