. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment . € B^ 'Illi / mile: TWO TARGETS SEPARATED BY MORE THAN THE BEARING RESOLUTION ANGLE APPEAR AS TWO SEPARATE PIPS. Figure 4-3.—Bearing resolution. While the result of good resolution in range and bearing is a clear, sharply defined PPI picture, giving an accurate contour of land and definite pips for small targets, a Radar of poor resolution would have a blurred and fuzzy appearance with targets blending together on the scope. The resolution in range is a funct
. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment . € B^ 'Illi / mile: TWO TARGETS SEPARATED BY MORE THAN THE BEARING RESOLUTION ANGLE APPEAR AS TWO SEPARATE PIPS. Figure 4-3.—Bearing resolution. While the result of good resolution in range and bearing is a clear, sharply defined PPI picture, giving an accurate contour of land and definite pips for small targets, a Radar of poor resolution would have a blurred and fuzzy appearance with targets blending together on the scope. The resolution in range is a function of pulse length, pulse shape, and receiver fidelity. The returning echoes are successively amplified by each of the intermediate-frequency and video circuits of the receiver; should these circuits modify the returning echoes, poor range resolution will result. The optimum band pass of the receiver should consequently be from to times the reciprocal of the pulse duration in microseconds. As the pulse duration T in microsaconds is equivalent to 164T in yards any targets sepa- rated by less than this value will appear as a single target. The resolution in bearing is directly dependent on antenna beam width. For any set frequency, beam width is a function of the antenna dimensions, decreasing as the antenna dimensions increase. Fortunately, as we narrow beam width to improve resolution we increase the over-all gain of the an- tenna system. However, there is a practical limit of about 1° or 2° where further narrowing of the beam causes targets to be missed due to the small number of pulses that will strike it as the antenna scans the target.
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