SAM Electronics GmbH NG3028X25KW Manual Do Utilizador

ED 3038 G 232 / 01 (2002-06) 

b_r1_e33.fm / 21.06.02

If the normal refraction gradient for the radar wave in the maritime boundary layer of the atmosphere is
changed by external influences, subrefraction occurs when the transmitted beam is bent upwards away
from the earth’s surface, and superrefraction occurs when the transmitted beam is bent down towards the
earth’s surface.

In the case of superrefraction, false echoes of targets outside the set range of measurement can occur:
the echo of a transmitted pulse is not received and displayed until the occurrence of the CRT deflection
trace controlled by the next transmitted pulse or by the one after that. The resulting ghost echoes can
occur at any position. Since the position of ghost echoes depends on the pulse repetition frequency,
ghost echoes can be recognised as such by switching over the pulse length on the master radar.

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Every pulse length has a particular pulse repetition frequency assigned to it; therefore, when the

pulse length is changed, the repetition frequency changes too.

If the radar function is suppressed in particular sectors (because parts of own ship’s superstructure do
not allow the radar to function in these directions), these sectors are indicated on the PPI near the
compass scale.

Blanking sector