Abstract: A resonant length, helical antenna is provided. According to an embodiment, the antenna includes a plurality of filars having different lengths and that are separately excited in order to provide a wide bandwidth. The bandwidth of the antenna may be further increased by providing switches to selectively terminate an end of the filars in either an open circuit or a short circuit to ground. According to another embodiment, the antenna is provided with a single helical element. The antenna provides efficient operation across a wide bandwidth, particularly at frequencies having good penetration characteristics through the earth. In addition, the antenna provides a radiation pattern having good coverage along an axis of the antenna. The antenna is particularly well suited for use in connection with horizontal directional drilling operations in which it is desirable to avoid contacting underground objects.