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Communications, Marine (Continued from Page 16) aboard ship. These radiobeacons are installed aboard light vessels or in lighthouses at suitable positions along coast lines, generally where navigation is difficult, and their use has been described under the radio- beacon system in connection with radio direction-finders. The radio-beacons are in continu- ous operation during foggy or incle- ment weather in the vicinity of the radiobeacon and at certain stated pe- riods during clear weather, so that a vessel may receive a reliable check as to a fix when cloudy or overcast weather may have made celestial navigation unreliable. This system also provides the master with ad- vance information as to the weather ahead of the vessel. If the vessel is experiencing clear weather, and the radiobeacons ahead of the vessel are in continuous operation, this clearly indicates that fog or poor visibility can be expected. As an example of the use of radio- beacons, one master cf a large ves- sel has reported that he navigated his ship in a dense fog from Colum- bia river lightship (Oregon), up the coast of Washington, and through the Straits of Juan de Fuca, chiefly by use of his radio direction-finder and radiobeacons along the coast. When the fog finally lifted the vessel was abeam of Slip Point, as indicated by radio-direction-finder bearings, thus saving considerable time. On the other hand, the sinking of the Nantucket lightship in May, 1934, is a disaster which it appears might be laid to over-confidence in the accuracy of radio bearings taken by radio operators on the incoming ship, and which an intimate knowl- edge of the direction-finder, its pos- sibilities, peculiarities and limita- tions, on the part of the officer, might have prevented. Definite con- clusions in this case may not be drawn, however, until completion of the investigation of the incident, which, at the time of this writing, is still in progress. Time Signals It is essential to the navigator that his chronometers be accurate—with a known daily rate. In order to rate chronometers and check their accu- racy, radio time signals are trans- mitted from various stations through- out the world, their accuracy depend- ing upon the precision of the ob- servatory clocks, which ccntrol them. In the United States,, these signals are transmitted from certain naval radio stations a number of stated times each day, with an accuracy greater than that needed for navi- gational purposes. The signals are transmitted simultaneously on low, medium and high frequencies in most cases, thus enabling the navigator 38 to obtain a radio time tick in prac- tically any part of the world. In these modern days of radio there is no valid reason for unknown erors in chronometers, but the use of these signals does require a cer- tain amount of knowledge on the part of the ship’s officers concerning the location cf time signal stations, times of transmission, characteristics of signals, and proper choice of fre- quencies for the locality. Fathometers While fathometers employ sound as the transmitted and received im- pulse, their principles and construc- tions are very similar to radio equip- ment, in fact, the circuits which ac- tuate the device are nothing but the usual oscillatory and amplifying cir- cuits employed in radio. The value of the fathometer should be obvious to all seamen, particularly during foggy weather. However, like all other devices on board a ship, the deck officer must have a general knowledge of the fathometer and its peculiarities to use it to advantage. The received signal, which indi- cates the depth of the water under the keel of the vessel, is often de- pendent upon the strength of the transmitted signal, the depth of wa- ter, and the type of bottom over which the ship is steaming. The navigator must learn how these fac tors affect the performance of the fathometer, and to compensate for their variations when necessary, in order to provide a definite and ac- _ curate indication of the depth of wa- ter under the keel, Weather and Hydrographic Broadcasts At regular times each day there are transmitted from many radio sta- tions throughout the world a synop- sis of weather conditions for the lo- cality served by the radio station and also for the larger general sea areas. These broadcasts enable a master to draw up a weather map and predict the weather which his vessel may encounter. General forecasts for particular localities are usually included in the weather broadcasts, but these are often insufficient for the purposes of the ship. In areas infested by hurricanes or typhons, radio stations afford almost constant information regarding such storms, particularly concerning their path and speed of translation. Many ships can thank the radio for timely storm warnings. The weather bureau relies in part upon ships at sea for information upon which to base their weather reports and storm warnings. Hydrographic broadeasts are also sent by many radio stations. These broadcasts include items important to safe navigation such as the loca- tion and drift of derelicts or other dangerous objects, carrying away or displacement of navigational land- marks, or inoperative status of shore MARINE REview—August, 1934 navigational _ facilities. The im- portance of these warnings to ship- ping is readily recognized. Masters and deck officers should know how, when, and from where weather and hydrographic broadcasts ean be received for the locality in which they are operating. Provision is also made tc broadcast hydro- graphic or meterological information from ships at sea when the safety of navigation is endangered. As radio facsimile transmission be- comes more general, it will be pos- sible to transmit a complete weather map to ships at sea. This has al- ready been successfully accomplished, and in the future should be of much assistance to masters. Some Other Radio Aids There exists a number of other de- velopments in the radio field which may aid the navigator. These include a method of obtaining simultaneous bearing and distance on a_ beacon. This necessitates both an underwater sound receiver and a radio direction- finder cn the ship. Signals from a submarine bell or oscillator and from a radiobeacon are transmitted sim- ultaneously. The radio direction- finder aboard ship obtains a bearing on the fixed radiobeacon, while the time interval between the receipt of the radio signal and the sound sig- nal affords a fairly accurate meas- ure of the distance to the fixed radio- beacon thereby giving the navigator a fix in foggy weather. A new application of the radio direction-finder is appearing. It is well known that severe storms are accompanied by an excess of atmos- pherics or static, and it has been dis- covered that a radio direction-finder can observe and measure within use- ful limits the center of the at- mospheriec disturbance. Some years ago, a radio direction-finder was in- stalled aboard a naval vessel to de- termine the practicability of such use on board ship. The command- ing officer of that ship, by observing periodically the intensity of the static and its bearing, was able to plot the path of this circular storm and avoid the hurricane by proper changes of course. It is felt that this development will eventually prove of great benefit to mariners, but its use- fulness on board ship will be predi- cated on some knowledge of radio disturbances and radio direction-find- ers by the deck officers. Attempts are now being made to develop a device known as a ‘‘fog eye,’’ which, by use of infra-red or other emanations from various ob- jects, suitably amplified by means of radio circuits, will detect the pres- ence of objects in a fog at a cop- siderable distance, at the same time affording a bearing. The further development of this device is awaited with interest, (To be Continued)