CONVERSION OF RADIO BEARINGS 23 If the bearing is from a radio direction finder station ashore, the sign of the correction will be reversed to that given when the bearing is taken from the ship. Example.-A ship in latitude 37°20′ N., longitude 69°20′ W., by dead reckoning receives a radio bearing of 64° from a radio directionfinder station located in latitude 35°14' N., longitude 75°32′ W. Find the Mercator bearing of the ship from the station Radio direction-finder station latitude_ Middle latitude____ 35° 14' N., long. 75° 32′ W. 36 17 Diff. 6° 12' Entering table with difference of longitude=6°, which is the nearest tabulated value to 6°12', and opposite 36° middle latitude (the nearest tabulated value to 36°17') the correction 106' is read. The ship being east of the station, the correction is plus. The Mercator bearing will then be the radio bearing received plus the correction from the table, 64°00'+106' 64°+1°46′ 65°46′. Table of corrections, in minutes [Difference of longitude in degrees] = Mid. L. 2° 1° 12° 2° 22° 3° 32° 4° 42° 5° 52° 6° 62° 7° 72° 8° 82° 9° 912° 10° RADIO NAVIGATIONAL WARNINGS In general, radio broadcasts of navigational warnings contain information of importance to the safety of navigation, such as the position of ice and derelicts, defects and changes to aids to navigation, advice about mine fields, etc. In the United States, radio navigational warnings are compiled by the Hydrographic Office, Navy Department, and by the Bureau of Lighthouses, Department of Commerce. Those issued by the Hydrographic Office commence "Govt. Hydro." and end "Hydro"; "those issued by the Bureau of Lighthouses commence Govt. USLHS " and end" United States Lighthouse Service." Broadcasts frequently include warnings issued by both offices. 66 Scheduled broadcasts of navigational warnings are given in the Hydrographic Office Publication No. 205, Radio Aids to Navigation; a summary of such schedules is included in a sheet issued from time to time by the Hydrographic Office, listing broadcasts of United States Radio Stations. Major hydrographic broadcasts, generally covering the Atlantic and Gulf coasts of the United States, are sent out daily by Washington through Arlington (NAA) and Annapolis (NSS). Local broadcasts, for particular areas, are made from stations listed below. Emergency broadcasts are made immediately upon receipt of information regarding imminent dangers. The masters of every ship, which meets with dangerous ice, a dangerous derelict, a dangerous tropical storm, or any other direct dangers to navigation, should communicate the information, by all the means of communication at their disposal, to ships in the vicinity and also to the competent authorities at the first point of the coast with which they can communicate. Station Boston, Mass. (NAD) San Juan, P. R. (NAU) – Pensacola, Fla. (NAS). Local hydrographic broadcasts Area covered South of lat. 45°00' N. and north of Point Judith and Nantucket Shoal Lightship. Lat. 42°00' N. to lat. 38°30' N. Caribbean Sea north of lat. 15°00' N. and West Gulf of Mexico. FREE MEDICAL ADVICE TO SEAMEN BY RADIO Arrangements are made in various countries whereby mariners of all nationalities may obtain medical advice by radio. Requests for medical advice of an urgent nature should be preceded by the urgent signal in order to give them priority over all other radio traffic except distress communications. The International Code of Signals, 1931, contains a medical section. By use of this code in communicating with foreign stations, difficulties of language may be avoided. The case-stating system in this medical section gives the nature of the information which should be included in the request for medical advice. Whether the message is to be sent in code or plain language, it is recommended that the mariner read this section before preparing his message. The United States Bureau of Public Health maintains the following stations at which free medical advice by radio may be obtained direct: New York, N. Y., United States Marine Hospital No. 70. Alternate, United States Marine Hospital No. 21, Stapleton, N. Y. Key West, Fla., United States Marine Hospital No. 10. Governmental and commercial radio stations will transmit free messages addressed to any of the above stations. In order to avoid confusion and to make the practice uniform, all messages for transmission will be signed "Marine Hospital No. Marine Hospital No. -", or "Public Health Service Relief Station No. as the case may be. All coastal stations operated by the Radiomarine Corporation of America and the Tropical Radio Telegraph Co. offer free medical message service to ships of all countries. Messages received from masters of vessels reporting symptoms observed in a sick member of the crew are promptly forwarded to the nearest marine hospital, where the case is diagnosed by the medical staff from the information given in the master's message. A course of treatment is then decided upon and suitable instructions are transmitted to the vessel. No charge is made for radiotelegraphic service of such messages when they are prefixed by "DH MEDICO." The following is a list of Radiomarine Corporation and Tropical Radio Telegraph Co. stations on the Atlantic coast. The United Fruit Co. has established a gratuitous medical service, which is rendered from its hospitals in various countries of Central America and from the passenger ships in its service, and is available to the ships of all nationalities. In cases of emergency, free medical advice may be obtained by ships at sea by radio from the Panama Canal, through the radio stations at Colon, Balboa, or Cape Mala. Such messages should be addressed, "Govt. C. B., Medico Pancanal", stating briefly and clearly the symptoms to be treated; and should be signed by the master. Medical advice radiograms must be checked and sent "DH MEDICO." Such radiograms will be given preference over all other messages except SOS calls. Radiograms must be signed by the master and state briefly but clearly the symptoms of the patient. Medical advice will be phrased in language intelligible to the layman. Complete details relative to the service furnished by all companies is published in the manual, Ship Sanitation and First Aid, issued by the Seaman's Church Institute of New York. This information contains diagrams and a list of symptoms to be considered in preparing messages. In addition to the above, current information on this subject can be secured by referring to H. O. Publ. No. 205, Radio Aids to Navigation. WEATHER Prevailing winds.-The winds are westerly north of the thirty-fifth parallel, except in September and October, when they are northeasterly along the entire coast. The westerly winds extend to the thirtieth parallel from December to April, inclusive. Easterly winds prevail along the Florida coast. At Key West they are northeasterly, except during the summer months, when they are southeasterly. Northers. In the winter months heavy northers occur in the vicinity of the Straits of Florida. They blow generally from northwest to north, hauling, as a rule, northward and eastward, and rarely backing. Their approach is nearly always heralded by a heavy bank of clouds in the northwest, preceded by light airs from the contrary direction, and accompanied by a falling barometer; they commence with a violent squall, gradually settling to a fresh gale. Vessels caught in the narrower parts of the straits in these gales are subject to a most trying sea. Southeast gales also occur at intervals during the winter months in the vicinity of the Straits of Florida. They usually commence to blow at about east-northeast, freshening rapidly with a falling barometer and rising thermometer and, hauling southward and eastward, obtain their greatest force at about southeast. Fog. The percentage of fog is highest from March to June, reaching a maximum of 30 percent of days with fog near the mouth of Chesapeake Bay in June. This percentage decreases to 10 at Hatteras, but fog can be expected as far south as Florida. STORM WARNINGS Storm warnings are displayed by the United States Weather Bureau on the coasts of the United States and the Great Lakes. The small craft warning.-A red pennant indicates that moderately strong winds that will interfere with the safe operation of small craft are expected. No night display of small craft warnings is made. The northeast storm warning.-A red pennant above a square red flag with black center displayed by day, or two red lanterns, one above the other, displayed by night, indicates the approach of a storm of marked violence with winds beginning from the northeast. The southeast storm warning.-A red pennant below a square red flag with black center displayed by day, or one red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the southeast. The southwest storm warning.-A white pennant below a square red flag with black center displayed by day, or a white lantern below a red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the southwest. The northwest storm warning.-A white pennant above a square red flag with black center displayed by day, or a white lantern above a red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the northwest. Hurricane, or whole gale warning.-Two square flags, red with black centers, one above the other, displayed by day, or two red lanterns, with a white lantern between, displayed by night, indicate the approach of a tropical hurricane, or one of the extremely severe and dangerous storms which occasionally move across the Great Lakes and Atlantic coast. These warnings are displayed at all stations on the Atlantic and Gulf coasts of the United States and on the following islands in the Atlantic: Jamaica, Turks Island, Bermuda, Haiti, Curacao, Puerto Rico, Virgin Islands of the United States, St. Kitts, Dominica, Barbados, Trinidad, St. Lucia, St. Vincent, Grenada, and Cuba. The following are the storm-warning display stations within the limits covered by this volume: NOTE.-The Weather Bureau station at Cape Henry, Va., is equipped for day and night communication with passing vessels. The International Code is used by day and the Morse Code, flash-light, by night. Messages to or from vessels will be forwarded to destination. At lighthouses and lightships warnings are not displayed at night. Information relative to radiotelegraphic weather broadcasts will be found on page 18. WEST INDIA HURRICANES Tropical cyclones of the North Atlantic Ocean are usually designated as West India hurricanes, but actually many of these storms 2 At these stations barometers will be compared with standards. Daytime display only. 20712°-36-3 |