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SKETCH OF PRESENT RADIO SITUATION INFLUENCE ON TACTICS AND STRATEGY
By Lieut. Commander S.C. Hooper, U. S. Navy
The two largest radio concerns in the world are the British Marconi Company, of England, and the United States Naval Radio Service. The British Marconi Company is one of the most important commercial institutions backed by the British Government, and its lines of communication extend over Europe, India, Africa and Canada, with connections to the American Marconi Company in the United States. The United States Naval Radio Service comprises high-power radio stations on both coasts of the United States, in Panama, the Caribbean, Hawaii, Guam, the Philippines, Alaska, Peking, Vladivostok; in addition, all coastal radio stations in the United States, for communication between ships and the Coast, with four exceptions, are owned and operated by the United States Navy. There are about 120 of these stations. Each air station, there are about a dozen in all, is equipped with a naval radio station for the purpose of communicating with airplanes and dirigibles on patrol, for distances of several hundred miles from shore. The navy is developing in addition, a system of navigational radio stations (see appended list) on both the Atlantic and Pacific coasts for the purpose of assisting ships at sea in determining their positions. These latter are especially useful for vessels approaching the coast in thick weather. There are about 50 navigational radio compass stations completed. All naval vessels and all vessels of the United States Shipping Board are equipped with naval radio apparatus, operated by naval radio-men; also vessels of other branches of the government, including the coast guard, light vessels of the Department of Commerce, and the army. The army maintains and operates its own radio apparatus except for transports. There were nearly 5000 United States naval radio operators on watch on the ships of the seven seas on January 1, 1919, and a large personnel is required on shore to maintain and install the equipment. Prior to the entering of the United States into the war there were but about 500 operators in the service, with but some 50 radio stations. There were, at the signing of the Armistice, over 5000 men in the service and about 150 stations. The number of shipboard and airplane sets in service has increased from about 400 to about 4000. In addition, a large number of listening-in section base stations were established during the war, but these were of a temporary nature and have since been abandoned. Also the radio service equipped about 15 air stations abroad with naval radio apparatus.
One of the largest problems assigned to the naval radio service at the beginning of war was the development of a transatlantic radio system capable of replacing the cables. Early in the war some of the cables became disabled, being cut by German submarines and otherwise, and it became impossible to repair them due to the torpedoing of cable ships by submarines. It was feared that the entire cable service might at any time become disabled due to submarines. At that time it was only possible to rely on radio communication across the ocean during certain times of the day when static and absorption of signals was a minimum and only about 30 per cent of the time during the summer months. Within one year various improvements were made and new stations constructed, and old stations equipped with new apparatus to the extent that to-day we are able to handle about one-third of the cable business by radio. During the past summer the total reception of signals, both ways, averaged 98.5 per cent as compared with 30 per cent the previous summer.
One of the principal means of increasing the traffic has been the introduction of automatic high speed transmitting and receiving apparatus. Certain stations are now being operated automatically at speeds of from 50 to 100 words per minute as compared with an average of less than 20 words per minute when using hand sending. All reception from Europe, from the high power stations in Lyons, Rome, Nauen, Carnarvon (Wales) and Nantes (France), is done at Otter Cliffs, near Bar Harbor, Maine, and direct wires to Washington are used to communicate the messages to Washington. The transmitting keys at the high power stations in the United States are operated automatically by means of distant control lines from the keys located" in the Navy Department, Washington. For example, the key in the Annapolis Station is pressed by the operator in Washington. During the war two additional receiving stations were maintained at Belmar, N. J., and Washington, respectively, for receiving signals from Europe. These stations were considered as stand-by stations and only supplied the parts of the messages which Bar Harbor failed to copy. The two greatest obstacles to reliable trans-oceanic communication were static and destruction of aerials by winter ice and winds. The static was overcome by using combinations of underground receiving aerials and balanced loops. The difficulty due to breaking of aerial wires by ice forming on the wires was overcome by heating the aerial wires by means of direct current supplied from the main generating machines at the radio stations.
The high power apparatus used is generally the arc and the Alexanderson alternator. Both are quite efficient. The alternator is slightly superior to the arc.
Following the surrender of the German Navy our experts have had an interesting opportunity to compare our own radio apparatus with that of the Germans. It had always been the opinion, among the officers of our own service, that the German apparatus was far superior, as the Germans were so noted as scientists. Greatly to our surprise it was found that the German ships not only were equipped with inferior apparatus, but that they had not equipped their vessels along the line of most recent developments in direction finders, submarine listening-in devices, and sharply tuned instruments. These secrets must have been known to the Germans and the experts are at a loss to understand this lack of equipment on their vessels.
Recent naval radio development has been along the following lines:
(1) Radio compass, for taking bearings by means of received signals.
(2) Radio telephone.
(3) Radio applied to aircraft.
(4) Increased ranges for communication.
(5) Improvement in sharpness of tuning, resulting in larger number of simultaneous communications, without interference.
(6) Underwater reception of signals.
(7) Fire control by radio.
The Radio Compass.—A large number of ships, principally destroyers and transports, have been equipped with the radio compass. This instrument consists of a receiver and an aerial, the latter being merely a revolving coil about four feet square. When the coil is in the plane of the incoming signal, the apparent signal intensity is greatest. By this principle the bearing of an incoming signal can be measured, at distances up to about 50 per cent of the distance of ordinary reception from any particular transmitting station. The time consumed in taking a bearing is about one minute. The accuracy of the reading depends principally on the personnel. It takes several weeks of constant practice for an operator to become an accurate measurer of radio compass signals. At least once a year the curve of errors for the radio compass should be determined by swinging ship, in a manner very similar to that used for determining deviation for the standard compass. With a carefully calibrated radio compass, a gyro repeater mounted in the radio compass room for comparison, and an experienced operator, it is possible to obtain accuracy on board ship within one or two degrees.
There are shore radio compass stations near the entrances of each of the principal harbors on the Atlantic Coast, including Boston, Newport, New York, Delaware Capes, Chesapeake Bay entrance, and Charleston. A ship may call for position within 200 miles of any of these stations and obtain it with a fair degree of accuracy. The nearer the ship is to the compass station the more accurate becomes the position given by radio. It is reasonable to expect roughly an average of one-quarter mile error close in shore, one mile at a distance of 20 miles, two miles error at a distance of 50 miles, and four miles error at a distance of 100 miles. The fact that the radio compass bearing is fairly dependable should not in any way relieve the navigator of the ordinary precautions, such as taking soundings and reduction of speed when nearing port in thick weather.
From the foregoing it becomes evident that the adoption of the radio compass to naval use introduces a new factor which must be considered in naval strategy, for being able to obtain the location of a ship by means of radio means that there must be very little radio signaling carried on by opposing forces in war time, if they desire to avoid being located accurately, by the other side.
By virtue of the use of radio telegraphy, it has become the practice for the force commander to shift his arrangement and disposition of forces quickly from time to time, as circumstances develop, merely by radio. The radio compass makes the use of radio increasingly dangerous, and requires more careful planning in conferences and written instructions in advance.. Study must, therefore, be given to means of circumventing this situation. In the first place it may be desirable to detail special decoy ships for the purpose of using their radio in an endeavor to mislead the enemy as to the strategic intentions; secondly, the power used for tactical maneuvers must be limited to the range of visibility, in order that the force commander's signals may not be overheard by the enemy; and thirdly, it will be necessary to arrange that the necessary exchange of radio information, using high-powered transmission, be done by means of messages so brief that the opponent operators will not have sufficient time to adjust the compass for the purpose of obtaining a bearing. This may require the rearrangement of the signal book in such form that a short code word will be sufficient to transmit a considerable amount of information. Shifting widely between wave lengths at predetermined intervals may be of some assistance in avoiding the enemy's compass listeners, in this respect.
A careful and systematic arrangement must be developed by our own vessels, and by the establishment of additional listening in compass stations, in order to insure that our operators may hear and locate the signals of any enemy craft which transmits by radio.
By virtue of the ability of the shore radio compass stations to give the navigator an accurate position regardless of visibility conditions it is possible for the fleet to make port under weather conditions which would otherwise render this difficult if not impossible. Therefore, the radio compass is an instrument which will greatly assist the commander-in-chief in greater freedom of movement by making quick retreat to a friendly port always possible.
Scouting airplanes and dirigibles are being equipped with radio compass outfits which will be of great assistance to these vessels in returning to port, and in locating their mother ships at sea.
By using the radio compass it is possible easily to make contact possible between vessels of our own fleet, in thick weather. This instrument proved valuable in this respect, during the war, assisting escorts to make contact with troop convoys, contact in thick weather being a matter of chance without the radio compass.
The Radio Telephone.—This instrument has recently been supplied to practically all naval vessels, and has proved particularly useful for aircraft signaling, for maneuvering submarine hunting squadrons, and as a convenience in the fleet at anchor, for arranging about supplies, athletic events, etc., where flag signaling is too slow and cumbersome. Experiments are being made by the fleet to determine whether the radio telephone will prove superior to the radio telegraph for tactical maneuvers. In the course of two or three years the art will have sufficiently advanced to make possible simultaneous use of the telephone and telegraph, without interfering one with the other. At present this is not practicable, and the telegraph must be silenced when the telephone is in use and vice versa, when used on the same ship.
The telephone will probably be found to be inferior to the telegraph for strategical purposes due to the difficulty in speedily transmitting cipher and code by telephone as compared to the telegraph, also to the fact that military information may be more concisely and clearly transmitted by carefully worded message. The telegraph is less likely to err than the telephone. Therefore it would appear that the telegraph will always be the primary means of communication for strategical purposes, and probably for tactical purposes. For convenience in administration the telephone will undoubtedly prove superior to the telegraph, but the use of the telephone will have to be carefully regulated in order not to interfere with the telegraph, at least until the art has solved the problem of simultaneous use of both.
For aircraft, where saving in weight is such an important factor, the telephone is preferable to the telegraph, as an additional man as operator is not necessary, the pilot himself doing the talking. Possibly as aircraft becomes larger and the weight factor becomes less important, the same rules will apply to the use of the telephone vs. telegraph for aircraft, as for ships.
Small tactical groups of vessels, such as subchasers and aircraft used in hunting submarines, find the telephone indispensable, as much information of value can be quickly transmitted by telephone which would be impossible by telegraph, due to the special nature of the work.
The radio telephones installed on naval vessels are efficient for communication for ranges of 20 miles, often much greater; those on subchasers and smaller craft for ranges of 10 miles. One of the transports carries an experimental radio telephone capable of transmitting voice 800 miles.
Radio Applied to Aircraft.—Airplanes and dirigibles used as scouts are dependent upon radio to provide communication with their flagships and with the bases on shore. Spotting planes are equipped with radio for reporting fall of shots.
Two types of apparatus are furnished airplanes; short range (5 miles range) telephone transmitters for use in spotting planes and for maneuvering planes in formation; and long range combined telephone-telegraph transmitters for use in scouting machines. The latter have a range of roughly 150 miles when using telegraph. When using telephone the range is reduced to about 75 miles due to the difficulty in receiving telephone through the noise of the airplane motors. Dirigibles are equipped with 200mile range transmitters, combined telephone-telegraph type.
A direction finder (radio compass) is now being supplied the latest type airplanes. By means of this instrument airplanes should be able to navigate back to their bases and mother ships in foggy weather. The airplane radio compass is efficient up to ranges of 75-100 miles when receiving from ordinary coastal and ship stations.
The principal influence on strategy, because of radio on aircraft, is to increase the radius of action of the airplane as a scout. Its value in tactics concerns the quick and accurate report of fall of shots. Spotting by aircraft observers will increase the accuracy of fire two or three hundred per cent, providing the radio is skillfully used.
Increased Range of Communication.—The range of radio has been greatly increased in the past two years due to the improvement in amplification of signals in the receiver and in anti-static antennae, also to increased efficiency in transmitters. Battleships, flagships, cruisers, and fuel ships have been equipped with arc type transmitters having reliable transmitting ranges of 800 miles by day (1500-2500 miles by night). A certain proportion of destroyers are being equipped with arc type transmitters which may be expected to give reliable ranges by day of at least 500 miles (over 1000 miles by night). The majority of destroyers have a reliable radio range of 300 miles by day. Improvements in receiving arrangements at shore stations has made reliable trans-oceanic communication possible. This is important from a strategical standpoint, as cables are very easily interfered with by submarines. It is not only possible for a submarine to cut a cable but it is a simple matter for the submarine to listen in, by inductive means, to the cable conversations, thereby intercepting the messages. This should be borne in mind in war time, and great care given to the careful enciphering of confidential cable messages. The efficiency of the trans-oceanic radio service has advanced to the stage wherein active competition with cable lines is practicable. Whether the radio will ultimately replace the cables is a matter of conjecture. Radio communication is cheaper than cable communication due to low initial and maintenance costs. The future of radio in this connection depends largely on whether the advance in the art will be sufficient to accommodate sufficient numbers of pairs of communication without causing too much interference.
Underwater Signaling by Radio.—It is now possible for submerged submarines easily to receive radio signals from ships, shore stations, etc. Efficient reception underwater from aircraft in flight is not yet practicable. A submarine can cruise with its aerial submerged 10-20 feet below the surface and overhear the various radio conversations which are carried on. To date no means have been developed by which the submarine effectively transmits radio signals using a submerged aerial.
Use of Radio for Fire Control.—Radio is of great value for fire control purposes generally, not only for airplane spotting in the fleet, but for artillery spotting on shore, and for concentrating the fire of several batteries on one target, also for exchanging ranges between fire control stations. Difficulties due to interferences between many stations operating within limited areas are being overcome by replacement of old type apparatus with modern continuous wave sets, and the addition of directional receiving aerials.
The use of radio for military purposes and for commercial purposes is increasing with rapid strides. The control of the aerial torpedo by an airplane is pretty well perfected, and there is considerable hope that an underwater torpedo controlled by radio from a guiding airplane will develop as a useful weapon. The limit of power of large caliber guns seems to have been about reached and for longer accurate ranges the radio controlled torpedo is the logical line of development, therefore our tactics and strategy should be guided with this in mind. We must look to the day when the aircraft, radio, torpedoes and submarines play most important roles in naval warfare.
The use of the various radio facilities which are possible is dependent entirely on skilled personnel. It is absolutely essential that the radio officer of each capital ship, and of each flotilla or group of destroyers, submarines and aircraft, be a skilled operator and constantly on the " wire." Failing in this no advance is possible. Flag officers can do the greatest good in advancing present day development by taking a keen interest in insisting on this important point. The whole future of strategy, tactics, information, fire control, and torpedo control is absolutely dependent upon radio telegraphy and radio telephony. This must be recognized and suitable provision made properly to develop personnel, material and operation plans to anticipate the situation.
RADIO COMPASS STATIONS
Atlantic Coast
Cross Island, Maine. Mantoloking, N. J.
Bar Harbor, Maine. Cape May, N. J.
Damiscove Island, Maine. Cape Henlopen, Del.
Appledore Island, Maine. Bethany Beacli, Del.
Gloucester, Mass. Hog Island, Va.
Deer Island, Mass. Smith Island, Va.
Fourth Cliff, Mass. Cape Henry, Va.
Cape Cod, Mass. Cape Hatteras, N. C.
Nantucket, Mass. Cape Lookout, N. C.
Chatham, Mass. North Island, S. C.
Price's Neck, R. I. Morris Island, S. C.
Watch Hill, R. I. Burrwood, La.
Montauk, L. I., N. Y. Pass a Loutre, La.
Fire Island, N. Y. Grand Island, La.
Rockaway Beach, N. Y. St. Augustine (Projected).
Sandy Hook, N. J.
Pacific Coast
Point No Point, Wash. Cape Arago, Calif.
Admiralty Head, Wash. Eureka, Calif.
Smith Island, Wash. Point Reyes, Calif.
Cattle Point, Wash. Farallon Islands, Calif.
Lime Kiln, Wash. Bird Island (Point Bonita). Calif.
New Dungenes, Wash. Point Montara, Calif.
Slip Point, Wash. Point Arguello, Calif.
Tatoosh Island, Wash. Point Conception, Calif.
Ozette Island, Wash. Point Hueneme, Calif.
Ocean Park, Wash. Cape Avalon (Santa Catalina), Calif.
North Head, Wash. Point Loma, Calif.
Tillamook Head, Wash. Chy, Calif. (Imperial Beach).
Ft Stevens (Clatsop Spit), O. R.