|June 10, 1910||
By W. W. Bradfield
(Of Marconi's Wireless Telegraph Co., Ltd.)
Summary—After discussing the advantages and progress of wireless telegraphy
for marine purposes, the author describes the wireless plant used on board
ship in detail. This may be classified as transmitting, receiving and emergency
apparatus. In conclusion, particulars are given of the number of naval
and mercantile marine stations in operation in the various countries.
Recent progress to this position has been very rapid. At the beginning of 1909 (after eight years of development) there were 125 ships of the mercantile marine fitted with Marconi apparatus. At the end of 1909 the number had risen to nearly 300, and at the present time the total is about 350, and is continuing to increase at a high rate. This increase has been accompanied by a marked development in the number of land stations erected, in course of erection and under consideration. And, apart from these conspicuous developments, the use of wireless telegraphy has become practically universal in our own and other navies, having been extended from battleships and cruisers to destroyers and submarines. There is every indication that what is now standard practice in the Navy will tend to become so in the mercantile marine--that is to say, the example set by the leading passenger steamship lines will be followed by all ocean-going and Channel passenger boats and also by cargo boats. The advance will probably be cumulative, as each installation on sea or land increases the value of the service to every ship making use of it.
It is interesting at this stage to survey the progress made on the principal trade routes.
North Atlantic--This is the route where wireless telegraphy has been most developed, owing in a large measure to the chain of shore stations established by the Marconi Company in Great Britain, Canada and the United States. All the leading vessels plying between European ports and North America are equipped, the total being 130, belonging to British, French, German, Dutch, Italian, United States and Greek companies. Under an agreement made last year, the shore stations of the Marconi Company in Great Britain passed into the hands of the Post Office, with the exception of the high-power station at Poldhu and Clifden, the former being used for the transmission of news to Atlantic liners and the latter for the trans-Atlantic service.
South Atlantic--The great route between Europe and South America comes next in order of importance. Eighty-five ships are already equipped, owned by the Royal Mail Steam Packet Co., the Koninklijke Lloyd, and the principal Italian companies. With the completion of the long-range station at Coltano and the erection of shore stations in Brazil and the Argentine, further developments in this important trade route are certain to take place. Coast stations have been erected at Guaratiba, Ponta Negra, Ilha Raza and Rio de Janeiro in Brazil; at Punta del Este, in Uruguay; and at Bernal, in Argentina, on the River Plate.
South African--Substantial progress has been made on this route. The Aberdeen Direct Line (Rennie Brothers) has used wireless telegraphy for some time, and the Union Castle has made a start with the ss. "Balmoral Castle." A Marconi station is in course of erection at Durban, and when it is ready the White Star liners in the New Zealand service will be fitted. The White Star Australian boats are all being equipped. Further advances will follow the erection of shore stations by the Cape Government.
Eastern Route--The potentialities of wireless telegraph developments on the great route through the Mediterranean to India, China and Australia are enormous. Eleven P. & O. vessels and sixteen Dutch vessels trading to Java are already fitted with Marconi apparatus. The ss. "Otranto," of the Orient Steam Navigation Co., is the first ship of this line to carry an equipment, and it is intended to fit the entire fleet during the coming season. The Commonwealth Government has made a beginning with a scheme for a series of shore stations, and arrangements are being taken for a number of stations at points intermediate between Australia and this country.
The development of regular communication between an increasing number of moving stations has necessitated not only a carefully devised organisation, but a uniform method of working. This, in turn, has necessitated a practical standardisation of apparatus. At the same time, the demand for absolute reliability in the hands of ordinary operators has led to the evolution of a type of apparatus which is free from complications and is constructed to work continuously without derangement. From the accompanying illustrations it will be observed that most of the working parts are contained in solid boxes, which protect them from damage and limit the responsibilities of the operator to superficial adjustments and the ordinary business of receiving and transmitting messages. The advance in electrical design has been accompanied by close attention to mechanical detail, with the result that failure on the part of the apparatus itself is practically unknown.
These points will emerge more clearly from the following detailed description of the standard 1½ kw. Marconi set usually installed on ships. The range of these sets varies from 70 to 300 nautical miles, according to the height, shape and length of the aerial, these factors in turn determined by the dimensions of the ship; while the night range may be anything from two to three times the day range, according to the conditions of the atmosphere. They are designed to produce waves of 300 and 600 metres, with a simple changeover; and the receiving apparatus provides for tuned reception of all waves between 100 and 2,500 metres, the range of reception depending on the aerial available and the power of the corresponding station.
Current (D.C.) is obtained from the ship's mains and led to a rotary converter, which supplies alternating current to the main terminals of a switchboard. (Emergency apparatus is always installed for working off a battery of accumulators in the event of the ship's supply failing--as was the case with the "Republic" after the collision.) The converter is designed to give an output of 1½ kw., and to take current from the direct-current supply available. It has four poles and runs at 1,500-1,800 revs. per min., with a frequency of 50 to 60 periods. Variation in speed is obtained by the field regulator.
Transmitting Apparatus--The low-frequency circuits consist of an adjustable inductance, the coils of a magnetic relay key, and the primary of a potential transformer connected in series and then to the two-line terminals of the switchboard. This circuit is opened and closed by the main switch, and operated by a Morse key actuating electrically the relay key. (Figs. 1, 2 and 3.)
The secondary of the potential transformer connects at the discharger through two air core protecting chokes with the primary high frequency circuit. The transmitter condenser is connected in series through a frequency tuning inductance to the other side. Between them is connected the primary of an oscillation transformer or transmitting jigger. The secondary of this transformer is connected at one end to the aerial and at the other to the top plate of a micrometer spark gap, the bottom plate being "earthed" by connection with the iron shell of the ship. A tuning lamp and choke are put in shunt with a short length of the wire connecting the jigger secondary to the micrometer spark-gap. The transmitting set is completed by an aerial tuning condenser, which is used only when it is necessary to decrease the natural period of the aerial circuit in the transmission of the 300-metre wave.
Receiving apparatus--The connection of the receiving apparatus with the aerial circuit is made at the top plate of the first micrometre spark-gap. From here a lead is taken to the aerial terminal of the tuner, the earth terminal of the tuner being connected to the bottom plate of the micrometer spark-gap.
The primary terminals of a magnetic detector are connected to the tuner, and the secondary terminals to a telephone and shunting telephone condenser.
Emergency apparatus--In this a battery of accumulators, charged by the ship's dynamo, provides current to work an induction coil. A separate key is used for operating; or, in special cases where a special change-over switch is provided, one key is used for operating both circuits.
The aerial lead-in is connected, by means of a flexible wire, to a socket on an insulating pillar, which in turn is connected to one end of the induction coil secondary, the other end of which is connected to earth. When receiving, the aerial terminal of the tuner is connected by a flexible and plug to the socket on the insulating pillar.
A full description of the details of the apparatus would occupy too much space, but the following particulars include the salient points about the more important parts of the transmitter.
Spark Discharger--The mushroom-shaped electrodes, which are of cast iron, are mounted on ebonite insulated brass rods and placed in a teak silence box lined with asbestos and lead. (Fig. 4.) Lime is placed in a removable zinc tray to absorb the acid produced by the spark. The gap is adjusted by turning the electrodes on their threaded brass supports. A protective point spark-gap shunting the main gap is set for a fixed gap to protect the condensers against excessive voltage.
Half-Plate Condenser--This is in two parts, each with 36 glass plates interspaced with 35 sheets of zinc. Ninety-four plates are active, the others being guard plates. They are 1/10 in. thick, and are individually tested to 27,000 volts. The container is filled with high-flash insulating oil. For the short wave the two parts of the condenser are connected in series, and have a capacity of about 0.016 mfd. With the long wave, in parallel, the capacity is about 0.065 mfd. The condenser is seen in Figs. 5 and 6.
Variable Coupling Oscillation Transformer or Transmitting Jigger--The primary and secondary windings are provided respectively by two coils of heavily-insulated wire, the former of one turn, and the latter of seven turns. It is at this point that the wave-generating and wave-radiating circuits are coupled together. For the purpose of adjusting the coupling between the circuits the secondary is made to slide laterally over the primary. On each oscillation transformer is a scale which gives approximately the percentage coupling between the two windings.
Aerial Tuning Inductance--Tappings are made at various points on 20 turns of insulated wire, and brought to eight insulated terminals in front of the box.
Aerial Lead-in--This is a ½ in. metal rod in a long ebonite tube, which passes through a cast-iron gland fixed on the roof of the cabin. A zinc cone is fitted to the external end of the rod to ensure that a considerable length of the ebonite will remain dry in all circumstances. A shackle head on the cone takes the strain of the aerial, and prevents the connection being worked loose by the vibration of the aerial wire. Three ebonite discs spaced along the external part of the ebonite tube prevent surface sparking in the event of heavy weather causing the insulator to be wet with salt spray. (Fig. 7.)
Earth Arrester Terminal--This consists of two round brass plates separated generally to about 0.01 in. by discs of mica. The wires to the ship's earth connect with the bottom plate. The top plate (seen in Fig. 8) is connected to the earth of the oscillation transformer and the aerial terminal of the tuner. When transmitting, the top plate sparks on to the bottom plate and connects direct to earth. When receiving, the top plate remains insulated and the aerial oscillations find their way to earth through the tuner. The terminal, while serving as an automatic switch, also provides protection for the aerial against lightning.
Multiple Tuner--A means of tuning to the incoming signals of one given wavelength, and eliminating the signals of all other wavelengths, is provided by the three inductively-coupled adjustable circuits, the first connected to the aerial and third to the magnetic detector. The full range of 100 to 2,500 metres is obtained in four steps by a triple four-way switch, which simultaneously alters the amount of fixed inductance and capacity in each circuit. Accurate tuning is obtained by an adjustable tuning inductance and variable condenser in all circuits. Injury to the instrument when transmitting is prevented by a micrometre spark-gap, which automatically shunts the aerial terminal to earth.
Wavemeter--A wavemeter is provided to enable the transmitting circuit to be correctly adjusted to the international waves of 300 and 600 metres. It consists of an inductance coil with a fixed number of turns connected to an adjustable condenser. Across the condenser is shunted a high resistance asymmetrical crystal in series with a double-head telephone. The condenser is adjusted until signals are loudest in the telephone. A table affixed to the lid of the wavemeter gives the wavelength corresponding to each condenser reading. The range of the standard apparatus is 200 to 800 metres.
Aerials and Aerial Insulators--Bare silicon bronze wires are used for the aerials. The overall dimensions depend on the design of the ship. In shape the aerials are either a twin L or a twin T, the spacing between the twins being 12 ft. A 12 ft. 6 in. ash spreader usually supports the aerial at each end. The spreader has two bands each with two lugs, one taking an aerial strain insulator and the other one leg of the spreader bridle. The strain insulator commonly in use for short aerials is 3 ft. long and circular in section, composed of Palmer cord encased in rubber and vulcanised. It is designed for a working load of 10 cwt. and a breaking load of 30 cwt. Long aerials are supported on larger insulators in the same manner. Each insulator is covered with a special insulating preservative compound to protect the rubber and furnish a non-hygroscopic surface. The arrangement is seen in Fig. 10.
Fig. 11 is a diagram showing the connections of the wireless equipment on board ship.
Wireless Telegraphy in Operation
It is practically impossible to give any idea of the extent to which wireless transmission is in operation, not only on passenger vessels, but in the case of cargo boats, cable-laying vessels, lightships, private yachts and other classes of vessel apart from the navies of the world. But the following list of the communications effected day by day in the case of a typical Atlantic vessel will indicate the importance of wireless telegraphy in one of its most conspicuous phases--a trans-Atlantic voyage on a large liner:--
Tuesday, May 3rd.
|5.0 p.m.||Ship left landing stage.|
|6.55 p.m.||Communicated with "Cymric."|
|7.45 p.m.||" Rosslare.|
|7.50 p.m.||" "Megantic."|
|8.6 p.m.||" "Campania."|
|11.30 p.m.||" Liverpool.|
Wednesday, May 4th.
|12.30 a.m.||Communicated with Rosslare and Liverpool.|
|1.0 a.m.||Receiving press from Poldhu.|
|2.0 a.m.||Communicated with Rosslare and "Megantic."|
|2.40 a.m.||" Scheveningen.|
|3.15 a.m.||" "Cymric."|
|4.45 a.m.||" Crookhaven.|
|6.50 a.m.||" "Majestic."|
|7.30 a.m.||Arrived Queenstown.|
|9.5 a.m.||Communicated with Crookhaven.|
|9.40 a.m.||" Ryndam.|
|10.25 a.m.||" "Sardinian."|
|11.51 a.m.||" "Cymric" and "Monmouth."|
|12 Noon.||" Crookhaven.|
|12.56 p.m.||" Crookhaven.|
|1.20 p.m.||" "Iroquois" and Crookhaven.|
Thursday, May 5th.
|12.45 a.m.||Communicated with "Sardinian" and Crookhaven.|
|1.0 a.m.||Receiving from Poldhu.|
|3.5 a.m.||Communicated with Crookhaven.|
|3.20 a.m.||" "La Bretagne."|
|3.45 a.m.||" "Victorian."|
|4.0 a.m.||" Crookhaven.|
|4.10 a.m.||" "Sardinian."|
|8.0 a.m.||" "Cymric."|
|8.50 a.m.||" "Cymric."|
|9.6 a.m.||" "La Bretagne."|
|9.30 a.m.||" "La Bretagne."|
|10.0 a.m.||" "La Bretagne."|
|11.40 a.m.||" "Cincinnati."|
|2.30 p.m.||" "Cincinnati."|
|2.32 p.m.||" "Victorian."|
|4.5 p.m.||" "Kaiser Wilhelm der Grosse" and "Cincinnati."|
|4.15 p.m.||" "Numidian."|
|5.30 p.m.||" "Mount Temple."|
|6.19 p.m.||" "St. Paul."|
|7.15 p.m.||" "MountTemple."|
|8.30 p.m.||" "MountTemple."|
|9.30 p.m.||" "MountTemple."|
|10.40 p.m.||" "St. Paul," "Victorian" and "Kaiser Wilhelm der Grosse."|
|11.40 p.m.||" "Cincinnati."|
Friday, May 6th.
|12 Mid.||Communicated with "Cedric."|
|12.55 a.m.||" "St. Paul" and "Victorian."|
|1.0 a.m.||Receiving from Poldhu.|
|2.50 a.m.||Communicated with "Cedric."|
|3.0 a.m.||" Scheveningen.|
|3.5 a.m.||" "Amerika."|
|3.12 a.m.||" "Kaiser Wilhelm der Grosse."|
|3.15 a.m.||" "Cedric."|
|3.20 a.m.||" "Graf Waldersee" and "Kroonland."|
|3.50 a.m.||" "Victorian."|
|4.40 a.m.||" "Cedric."|
|8.40 a.m.||" "Kaiser Wilhelm der Grosse."|
|9.20 a.m.||" "Kaiser Wilhelm der Grosse."|
|11.25 a.m.||" "New York."|
|12.6 p.m.||" "Cedric."|
|2.55 p.m.||" "Kaiser Wilhelm der Grosse."|
|8.45 p.m.||" "Kronprinz Wilhelm."|
|9.40 p.m.||" "Kaiser Wilhelm der Grosse" and "Kronprinz Wilhelm."|
|11.50 p.m.||" "Kaiser Wilhelm der Grosse."|
Saturday, May 7th.
|1.0 a.m.||Receiving from Poldhu.|
|3.1 a.m.||Communicated with "Kaiser Wilhelm der Grosse," "Kronprinz Wilhelm" and "Graf Waldersee."|
|5.0 a.m.||" Cape Race.|
|7.30 a.m.||" "Kaiser Wilhelm der Grosse."|
|8.0 a.m.||" "Kronprinz Wilhelm."|
|11.55 a.m. E.S.T.||" "Chicago."|
|11.35 a.m.||" "Kaiser Wilhelm der Grosse."|
|12.10 p.m.||" "Carmania."|
|12.25 a.m.||" "Carmania."|
|12.38 p.m.||" "Zeeland."|
|7.30 p.m.||" "Prinzess Irene."|
|7.40 p.m.||" "George Washington."|
|9.40 p.m.||" "Adriatic."|
|10.0 p.m.||Receiving from Cape Cod.|
Sunday, May 8th.
|12.10 a.m.||Communicated with "La Lorraine."|
|12.35 a.m.||" "President Lincoln."|
|12.47 a.m.||" Cape Race.|
|1.5 a.m.||" "Adriatic."|
|2.35 a.m.||" "Kaiser Wilhelm der Grosse."|
|3.17 a.m.||" "Oceanic."|
|3.46 a.m.||" "President Grant."|
|7.12 a.m.||" "Argentina."|
|8.56 a.m.||" "La Lorraine."|
|8.40 a.m.||" "Martha Washington."|
|8.41 a.m.||" Cape Race.|
|8.53 a.m.||" "Graf Waldersee."|
|11.20 a.m.||" "Argentina."|
|12 Noon.||" Cape Race, "Graf Waldersee" and "Kaiser Wilhelm der Grosse."|
|4.20 p.m.||" "Rhein."|
|5.10 p.m.||" "Kaiser Wilhelm der Grosse."|
|7.40 p.m.||" "Corsican" and "Empress of Britain."|
|8.10 p.m.||" Sable Island.|
|10.0 p.m.||Receiving from Cape Cod.|
Monday, May 9th.
|12.20 a.m.||Communicated with "Kaiser Wilhelm der Grosse" and Cape Race.|
|1.20 a.m.||" "Empress of Britain" and Sable Island.|
|1.30 a.m.||" "Grosser Kurfust."|
|2.0 a.m.||" "Empress of Britain."|
|3.45 a.m.||" Sable Island and "Prinzess Irene."|
|6.10 a.m.||" "Arabic."|
|6.20 a.m.||" Cape Race.|
|7.40 a.m.||" "Finland."|
|8.2 a.m.||" "Philadelphia."|
|8.7 a.m.||" Sable Island.|
|8.45 a.m.||" Sable Island.|
|9.30 a.m.||" Sable Island.|
|9.35 a.m.||" "Caledonia."|
|10.35 a.m.||" Sable Island.|
|11.55 a.m.||" "Kaiser Wilhelm der Grosse" and Cape Race.|
|2.36 p.m.||" "Prinzess Irene."|
|12.50 p.m.||" "Neckar."|
|1.55 p.m.||" "Prinzess Irene."|
|2.16 p.m.||" "Neckar."|
|2.30 p.m.||" "Kaiser Wilhelm der Grosse," "Oceanic" and Sable Island.|
|4.20 p.m.||" Sable Island.|
|6.50 p.m.||" "Kaiser Wilhelm der Grosse."|
|8.50 p.m.||" Cape Sable.|
|9.55 p.m.||" Sable Island.|
|10.15 p.m.||Receiving from Cape Cod.|
Tuesday, May 10th.
|12.25 a.m.||Communicated with "Graf Waldersee."|
|2.6 a.m.||" Siasconsett.|
|3.28 a.m.||" Siasconsett.|
|8.11 a.m.||" "Prinzess Irene."|
|8.40 a.m.||" "Grosser Kurfust."|
|8.45 a.m.||" Siasconsett.|
|1.25 p.m.||" "Prinzess Irene."|
|1.40 p.m.||" Siasconsett.|
|1.44 p.m.||" Cape Sable.|
|5.50 p.m.||" "Kaiser Wilhelm II."|
|6.45 p.m.||" "Nieuw Amsterdam."|
|6.50 p.m.||" "Oceania."|
|7.10 p.m.||" Sagaponack.|
|11.55 p.m.||" Sagaponack.|
Wednesday, May 11th
|12.30 a.m.||Communicated with Siasconsett.|
|4.45 a.m.||" Sagaponack.|
|5.10 a.m.||" Seagate.|
|7.19 a.m.||" Seagate.|
|8.10 a.m.||" Seagate.|
|9.40 a.m.||Ship docked New York, station closed.|
It may be of interest to observe that of all the communications effected as above noted, in only one case, namely, that of the Scheveningen (Holland) was the corresponding station not fitted with Marconi apparatus.
The use of wireless telegraphy on cable-laying vessels, yachts and other special classes of ship is increasing. At present the following cable-laying boats and private yachts have been equipped by the Marconi Company:--
s.y. "Iolanda," s.y. "Cassandra,"
s.y. "Lysistrata," s.y. "Niagara," s.y. "Florence."
c.s. "Mackay Bennett," c.s. "Colonia,"
The conditions under which cable-laying vessels have to work make the value of wireless telegraphy very conspicuous in their case. Repairs have to be carried out at long distance from shore, and as a rule the vessels have to return to port before instructions regarding subsequent work can reach them, with the result that expensive delays are frequently incurred. An example of the service which wireless telegraphy may render is supplied by the following extract (modified in details of wording) from the log of a cable-laying ship:--
On one occasion we were repairing a cable some 180 miles from the west coast of England, and required further information about electrical tests from the shore. A message was sent and received by another steamer equipped with a Marconi wireless installation and relayed by her on to England, the result being that in less than an hour we had a reply from London giving the desired information, and enabling the vessel to proceed with her cable-laying operations without delay.The standard equipment for marine work is either the 1½ kw. set just described or a 5 kw. set, where a disc machine takes the place of a spark discharger. Both sets are capable of exceeding their guaranteed limits. For instance, in the case of a certain destroyer, the guaranteed range of transmission was 60 miles, but nearly all of them exceeded 80 miles on their tests. In the case of a larger vessel, the guaranteed range was 100 miles and the realised range was 185 miles. Another war ship fitted with a 5 kw. installation exceeded her guaranteed range of 250 miles by more than 100 miles.
Considering that the inquiry was relayed, and necessitated a careful answer from headquarters, also relayed, the time occupied was remarkably short. On another occasion, when the vessel was on her way home from the completion of a repair off Ireland, a wireless message was received ordering her to the coast of France for another repair, thus saving a useless voyage back to London.
As already indicated, the number of wireless installations
on shore and on ships is increasing so rapidly that up to date official
statistics covering the whole of the world are impossible to obtain. The
following figures, taken from the Bulletins of the International Telegraph
Bureau, will give some notion of the extent of the business, but they must
not be taken as complete, since certain countries have not ratified the
Convention or made complete returns.
|Country||Number of naval ship stations,||No. of stations in the mercantile marine.|
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