In general, the invention is directed to techniques for locating an implanted object using an external antenna. The implanted object may be, for example, an internal antenna that facilitates recharging of and/or communication with an implantable medical device. An external device coupled to the external antenna drives the antenna with a plurality of waveforms. Asymmetry in the loading profile of the external antenna when it is driven by the plurality of waveforms allows the external device or another device to determine the location of the implanted object relative to the external antenna. The external device or other device may provide information to a user based on the determined location of the implanted object relative to the external antenna, such as information to help a user position the external antenna with respect to an internal antenna in embodiments in which the implanted object is an internal antenna.