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Radar System Engineering

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248 RADAR BEACONS [SEC.8.1<br />

4. Portable beacons. Small beacons have been used for marking life<br />

rafts and small target rafts.<br />

Airborne<br />

<strong>Radar</strong>.<br />

1. Fixed ground beacons. Beacons used with microwave radar having<br />

PPI presentation give most satisfactory navigational fixes by<br />

graphically locating the aircraft with respect to several known<br />

points on the ground. Figure 8.4 shows one of the AN/CPN-6<br />

beacons, a 3-cm beacon of high power designed for use in air<br />

navigation.<br />

FIG. S.4.—The AN/CPN-6 beacon. The .4N/CPN-6 is a hi..zh-nowered3-cm beacon<br />

interidedfor usein permanentiristallationson th~ g~ound.<br />

2,<br />

Special systems designed for measuring with great accuracy the<br />

ranges from two ground beacons at known positions have been<br />

used for mapping and blind bombing of high precision. Since in<br />

such systems there is no need for determining azimuth, lower frequencies<br />

can be employed advantageously, omnidirectional<br />

antennas can be used in the aircraft, and the beacon replies (which<br />

are then steady) can be presented on special indicators designed<br />

for ease in getting great accuracy of measurement.<br />

Beacons at longer wavelengths have been used in blindapproach<br />

systems.<br />

Shipborne beacons. Some beacons have been used for identifying<br />

ships, others for enabling aircraft to home on their carriers or on<br />

convoys.

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