PURPOSE: To improve the selection accuracy of the target airplane by reducing the received band width during the searching mode and the action of the rate memory.

CONSTITUTION: This apparatus is composed of a receiving section 2 which is adapted to separate and combine the bearing and elevation components in the frequency and make them separable with a demodulator 5, a mode indicator 10 for disignating various modes including automatic and manual tracking search modes and the like. In the aforementioned arrangement, when the mode signal from the mode indicator 10 is applied to the gate circuit 11 instead of the use of the video output including search mode and rate mode, the voltage of a frequency indicating voltage generator 9 extends to an intermediate frequency generator 4 to actuate a band varying element narrowing the band range to about one-twentieth of that when the video is generated. This allows the receiving of only the desired frequency provided that the difference between the incoming frequencies is over one-twentieth larger than that in the wide band range. Upon the end of the automatic search mode, the indicator 10 shifts to the automatic tracking mode and the gate circuit 11 is closed thereby making possible the receiving of frequency in the wide band range.