Radio mirror (Jan-Oct 1923)

RADIO DIGEST April 28, 1923 How Ocean Vessels Are Guided by Radio Waves Ether Signals from Submerged Cables Bring Ships into Harbor By Peter J. M. Clute ASIDE from the broadcasting of news and entertainment and the linking of widely separated points, Radio has many potential uses. Perhaps, one of the most useful developments in this line is the Radio piloting cable, with its great possibilities in the field of commerce and navigation. Submerged Cable The Radio piloting cable is essentially an insulated, electrically-charged, submerged submarine cable laid in a channel or an entrance to a harbor, and is used as an aid to navigation by serving as a guide to vessels entering during foggy, misty or hazy weather. Under such atmospheric conditions, the navigating officers are unable to pick up the buoys which are used end, along the channel to a point several miles away, usually at the entrance to the harbor. Current at a frequency of about 500 cycles per second is supplied to the cable, thus producing an alternating magnetic field around the cable. "Vessels equipped with special loop or "pick-up" coils mounted on each side and connected to suitable amplifiers are thus enabled to follow the lay of the cable by a simple comparison of the relative strength of signals received by the "pick-up" coils. Figure 1 shows a diagrammatic idea of the scheme. Magnetic Field The existence of a magnetic field about a conductor carrying current forms the basic principle of the Radio piloting cable. Figure 1 to mark the navigable channel. Ordinarily the vessel cannot proceed into the harbor until the fog or mist has raised. By the use of the Radio piloting cable, as demonstrated by practical tests and experiments with this system at several large harbor entrances, vessels with navigating bridges screened in so that the pilots could not see the channel, have successfully managed to keep to the course and dock in safety. The feasibility and practicability of the system was effec CND VIEW 5106 VIEW. CONDUCTOR. .LINES OP FORCE Figure 2 DIRECTION OP CURRENT FLOW tively demonstrated during these tests, inasmuch as the navigating officers, in each case, were able to pursue a course at either side of the piloting cable without any difficulty, although having no previous experience with the scheme. Cable Placed In Harbor The submerged insulated cable is laid along the harbor or channel bottom, extending from a power station at the shore KELLOGG SWITCHBOARD & SUPPLY COMPANY Chicago The magnetic field produced by a current of electricity always lies in a plane at right angles to the current producing it. In other words, the lines of force about a straight conductor carrying a current are concentric closed circles, of which the conductor is the axis. This is shown in Figure 2. If the direction of current through the wire is reversed, the direction of the lines of force will be reversed. It will be apparent from the illustration that the positive direction of the lines of force bears the same relation to the direction of current as the direction of rotation of a right corkscrew bears to the direction in which it advances. Likewise, to an observer looking along a conductor in the positive direction of the current, the positive direction of the lines of force will be clockwise. Circular Lines of Force Referring to Figure 2, the circular lines of force are further and further apart as the distance from the conductor increases. This is representative of the fact that the strength of the magnetic field near a straight conductor is greatest next to the conductor and diminishes as the distance increases. While the lines of force about HERE IT IS Just What You Have Been Looking For A VARIABLE RADIO RESISTANCE THAT MOUNTS ON PANEL IN A JIFFY Patents Pending. Real Radio Fans, in the building of their sets, will more than appreciate this device, which gives them a variable resistance which is adaptable for use in all Radio Hook-ups — in the grid circuit — as amplifier coupling resistance for both radio and audio freaueney — "B" battery resistances — antenna shunts — tuned loop circuits — resistance couplers for both radio and audio frequency, and many other places in the radio hook-up that tie amateurs' ingenuity will suggest. Has switch lever and seven carefully calibrated values of resistance of Ms megohm each between terminals. Protecting bakelite discs assure permanency of moisture-proof India ink resistance. Don't guess — it is important to have resistances properly adjusted to function with your other apparatus to get the best results from all tube sets. A Premier Variable makes this sure and easy. Code No. 250. Price... S 1.50 each DISTRIBUTORS — We make a most complete line of radio parts. Some territory open for live, responsible concerns. PREMIER ELECTRIC COMPANY Manufacturers Est. 1905 3800 Ravenswood Ave. Chicago, 111. a conductor permeate all space around it, the field becomes gradually weaker and weaker as the distance from the conductor increases, so that for all practical purposes it may be assumed that the field exists only in the space close to the conductor. The field strength decreases inversely proportional to the square of the distance from the conductor. Also, along all parts of a conductor in which the same current is flowing, the field is uniformly distributed. The Radio piloting cable, in consequence of the 500-cycle alternating current flowing in it, radiates a corresponding alternating magnetic field. With proper apparatus this field can be detected or "picked up" at a distance of up to 1000 yards. By this means, the position of the piloting cable can be located by sensitive receiving and amplifying equipment. Experiments to Find Range Experiments which have been made with the Radio piloting cable with the object in view of determining the useful range of operation, have been instrumental in securing valuable data for the further elaboration and development of the scheme. The detecting equipment consists essentially of two "pick-up" or loop coils, one being suspended vertically on each side of the vessel, from ten to 15 feet above the water-line. Figure 3 shows the installation. Each coil is made up of two hun dred to three hundred turns of number 12 or number 14 B. & S. gauge wire wound on a four-foot square loop frame. A double-throw selector switch permits connecting either detecting coil in circuit with a sensitive audio-frequency amplifier outfit. With this vacuum-tube amplifier, the comparative or relative strength of the signals picked up by the two coils will furnish the means of determining the DOUBLE^* THROW SELECTOR. _ SWITCH ? O. 'PICK-OP' COILS AT SIDE OF ' VESSEL Figure 3 vessel's position with reference to the location of the submerged piloting cable. The "shielding" effect of the ship's steel frame or hull exerts an unusual influence in that louder signals are obtained when the vessel is slightly to one side of the cable than when it is directly over the cable. In the latter position, the signal strength will be approximately the same from the two coils. "Make PERFECTION Your Selection" We Carry Only STANDARD Advertised Radio Equipment. Every Product Sold on a MONEY BACK GUARANTEE. Perfection Pays Parcel Post FRFF A $1-25 VOLTMETER OR AMMETER GIVEN WITH EACH ITDmr * **■«-■*-■ PURCHASE OF $5, OR OVER ^ JV.I1.H. MAGNAVOX LOUD SPEAKER TYPE R. 3 $27.45 FLEWELLING CIRCUIT Complete parts including DRILLED panel double coil Mounting and Honeycomb coils; only standard equipment used. FREE d»l 7 fj r* DIAGRAM «pl / . / D DICTAGRAPH PHONES $8.00 List. 3000 Ohms $5.95 N. & K. PHONES $6.50 6000 Ohms. Made in Germany ACME TRANSFORMERS $4.25 Type A 2 S $5.00 List KL0SNER Vernier Rheostats LIST $1.50 .59C REINARTZ CIRCUIT Complete parts including DRILLED PANEL. FREE d>11 O £ DIAGRAM «|> 1 1 .& O KAUFFMAN CIRCUIT Complete parts including DRILLED PANEL. FREE (h 1 fi nr DIAGRAM *p 1 D . V D TH0RDARS0N Transformers $4.50 LIST $3.25 BALDWIN PHONE Original Nathaniel. &A *7 C list $6.00. 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