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AP3302 Pt3 Contents

AP3302 Pt3 Section 1 Contents

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AP 3302 Pt. 3

Section 1


Basic Requirements Of A Pulse-Modulated Radar System

direction corresponds to the direction in which the aerial is pointing at that instant and each vertical trace moves across the screen in step with the aerial. Intensity modulation is used. The aerial scan is confined to a chosen 'sector', the limit of the swing often having a maximum value of +/- 80o.

b. Type E. This shows range against elevation. The timebase voltage is applied to the X-deflecting plates and the position of the trace in the vertical direction corresponds to the angle of elevation of the aerial. Intensity modulation is used.

c. Type F. This shows bearing and elevation errors for a single target. A timebase voltage is not required because range is not being measured. DC error voltages are applied to the X-plates for bearing error and to the Y-plates for elevation error. When there is no error, i.e. aerial pointing directly at the object, the target appears as a brig14 spot at the intersection of the two crossed lines.

d. Sector display. This shows ranges and bearings of targets over a given sector. It is similar to the p.p.i. but since the aerial turns from side to side through an arc instead of turning a full circle the display is a segment of a full p.p.i. display. The sector display shows the same information as a type B but the type B shows more detail because it uses more of the c.r.t. screen area.

e. Type J. This is a modification of the type A display. It uses a circular timebase to indicate range only, the trace being p (Pi) times longer than that for a corresponding type A display. A larger scale is thus obtained and targets close together in range can be more easily displayed. Deflection modulation is used.

i. Type L. This is a modification of the type A display. Two radar beams are used and the echoes due to each are placed back-to-back on the display. When the two blips are of equal size the aerial is pointing directly at the target. Bearing against range can be displayed in this way.


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