The ability to determine the direction of incident radio waves is useful in a wide variety of different applications. Measuring the direction of arrival for high frequency (HF) radio waves which have been propagated via refraction by the ionosphere is of particular interest for ionospheric sounding and thunderstorm monitoring, and is also useful for over-the-horizon radar and HF communications. The direction of arrival is commonly measured using wide aperture arrays of antennas. However, due to the long wavelengths of HF waves, arrays for measuring such waves must be physically large. A vector-sensing antenna system, using orthogonal triads of antennas to measure the electric and magnetic field components of the incoming waves, offers the possibility of making these measurements without requiring a large area or a large number of elements. In this talk we will consider the performance of various vector-sensing antenna configurations, and explore some of the difficulties that may be encountered. We will also show results measured from prototype antenna systems and show why some of the configurations may be difficult to implement, as well as one configuration that avoids some of the problems and may be able to form a useful vector-sensing antenna system.