Abstract: An automatic radio direction finding system employing an integrated antenna unit containing both sense and loop antennas in a single compact enclosure. Signal processing circuitries by means of which a low-frequency switching modulation is imposed on one of the antennas, as well as broad-band R-F preamplification and signal combining circuitry for the antenna outputs, are accomplished within the unit. The combining circuit output in the antenna unit, and the remote receiver input, have impedances matching that of a standard coaxial cable interconnect, such that the voltage dividing action effected by conventional antenna cable interconnect means is removed, permitting a small sense antenna of considerably less H.sub.e C.sub.a product to provide necessary sensitivity.