The blanking out or obscuring of weak radio signals by a stronger signal

Related Terms


The determination of distance by measuring the time interval between transmission of a radiant energy signal and the return of its echo. Since echo ranging equipment is usually provided with means for determining direction as well as distance, both func- tions are generally implied. The expression is customarily applied only to ranging by utilization of the travel of sonic or ultrasonic signals through water. See also RADIO ACOUSTIC RANGING, SONAR.


  1. A satellite which contains power source to augment the output signal (i.e., reflected only) as contrasted with ACTIVE SATELLITE; a satellite which is a passive reflector. 2. As defined by the International Telecommunications Union (ITU), an earth satellite intended to transmit radio communication signals by reflection.


A flag, sound, light, or radio signal meaning a vessel is threatened by grave and imminent danger and requires immediate assistance.


Coarse Acquisition - the radio signal on the L band frequency of 1575.42 MHz that civilian GPS receivers use. As opposed to the P code used by the US military.


Travel of a radio wave to the ionosphere and back to earth. The number of hops a radio signal has experienced is usually designated by the expression one-hop, two-hop, multihop, etc


The region in space within which the difference in amplitude of two radio signals (usually emitted by a signal station) is indistinguishable


The fluctuation in intensity or relative phase of any or all of the frequency components of a received radio signal due to changes in the characteristics of the propagation path. See also SELECTIVE FADING.


The minimum input signal required to produce a specified output signal from a radio or similar device, having a specific signal-to-noise ratio.


A buoy with equipment for automatically transmitting a radio signal when triggered by an underwater sound signal.


A radio transmitting station which emits a distinctive or characteristic signal so a navigator can determine the direction of the source using a radio direction finder, providing a line of posi- tion. The most common type of marine radiobeacon transmits radio waves of approximately uniform strength in all directions. These omnidirectional beacons are called circular radiobeacons. A radio- beacon some or all of the emissions of which are directional so that the signal characteristic changes according to the vessel’s bearing from the beacon is called a directional radiobeacon. A radiobeacon all or part of the emissions of which is concentrated in a beam which rotates is called a rotating radiobeacon.

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