A SHORT-WAVE DIRECTION FINDER USING A RING ANTENNA-ARRAY OF LOG-PERIODIC ANTENNAS

Phase methods of determining the direction to sources of radio radiati on have become widely used in the short-wave band [1]. Radio direction finders developed using such methods are based on the use of vertical antennas having a phase characteristic in the form of a circle. In di rection finders of this kind the phase difference between the voltages applied to the inputs of a two-channel receiver is equal to the path difference between the phase centers of two separated antennas. By mea suring the phase one can determine one of the angles of arrival of a b eam. To find two angles one needs to use three or four antennas spaced a certain distance from one another. The main drawbacks of existing d irection finders are the low interference protection when receiving th e useful signal, the limiting operating frequency band, ambiguity in d etermining the azimuthal angle, to overcome which a second system with a small antenna spacing is employed, which gives a unique but less ac curate readout of the direction, the need to use a phase shifter, cont rolled either manually or using an electric motor, which does not enab le the direction of a signal with rapid fading to be determined, and t he impossibility of using antennas which do not have fixed phase cente rs. In this paper we propose a short-wave direction-finding system whi ch is free from these drawbacks.