. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment. Loran; Radar. 28 OCEAN ELECTRONIC NAVIGATIONAL AIDS. -Tli.^ li nt at a cla-~ \ i iiliobeacon station, .locks showu at ihu k'ft. One of the it is convenient to synchronize stations in groups of three, and this grouping and synchronization has been extended to the whole system. Radiobeacons transmit on even frequencies in the band 285 to 325 kilocycles (i. e., 286, 288, 290, etc.). SIGNAL CHARACTERISTICS The radiobeacon is an aid to navigation and is therefore
. Electronic navigational aids; loran, radiobeacon, and radarbeacon systems and loran, radio-direction-finder, and radar ship equipment. Loran; Radar. 28 OCEAN ELECTRONIC NAVIGATIONAL AIDS. -Tli.^ li nt at a cla-~ \ i iiliobeacon station, .locks showu at ihu k'ft. One of the it is convenient to synchronize stations in groups of three, and this grouping and synchronization has been extended to the whole system. Radiobeacons transmit on even frequencies in the band 285 to 325 kilocycles (i. e., 286, 288, 290, etc.). SIGNAL CHARACTERISTICS The radiobeacon is an aid to navigation and is therefore made as con- veniently available to the navigator as practicable. Consistent with this idea, the characteristics assigned to radiobeacon stations in this country have been limited to brief and simple combinations of dashes and dots, corresponding in no case to more than a single International Morse code symbol. They are thus differentiated on the same principle as are lights along the coast, a system to which navigators are accustomed. The entire transmission for any station is a repetition of the assigned signal, without variation. There is a minor exception to this in the case of distance-finding stations. The advan- tage in this arrangement is that whenever a radiobeacon is heard its identity is immediately apparent, even to a navigator who is not a radio operator. There appears to be no diflBculty in differentiating radiobeacon signals from other transmissions, and therefore the use of a common distinguishing letter for all radiobeacons has been considered unessential. TYPE OF MARINE RADIOBEACON EMISSION All marine radiobeacon stations in the United States emit type A2 signals. This type of emission is obtained by either keying the modulating audio frequency or by the keying of the modulated carrier. Radio direction finders have generally been designed so as to be capable of taking bearings on either unmodulated continuous wave or modulated con- tinuous wave signals. MARINE
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