The direction finder consists of a horizontal beam (2), rotatable about a vertical axis (1) at the ends of which are mounted the cross frame aerials (3,4: 3',4'). Switching the frame aerials (3,4: 3'4') together in one circuit arrangement, results in a coaxial double frame configuration and in another circuit arrangement a coplanar double frame configuration, both formed from the virtually one surface frame aerials (5,5' 6,6') respectively. By the opposite switching of two frames in either the coaxial or coplanar double frame arrangement, sharp null positions displaced by 180 degrees are obtained, (in contrast to the differential switching of two rotary beam aerials, as with an Adcock), and also additional null points, which arise from the null points of the individual frame aerials. The desired null points can be displayed on an oscillograph in polar or Cartesian coordinates- pref. the latter - ensuring that the unambiguous determination of both sharp null positions can be obtained using the most suitable double frame aerial arrangement independent of the polarization.
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