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] Practical Ideas for the Engineer New Type of Radio Direction Finder Is Simple and Dependable—How To Take Care of Rope government departments, and others, are giving much a‘tention to the importance of providing on ship- board radio: direction-finding equipment by means of which the position of a ship cain be quickly and accurately de- termined. The matter is receiving at- tention in various foreign countries as well as in the United States. The pro- S HIPOWNERS, radio operators, vision of radio direction-finding equip- ment on a ship may eliminate serious delays caused by a ship being unable to enter port during a fog because its position, or the bearing of lighthouses is not known. In case of wreck such equipment may be the means of saving many lives. The radio direction finder is a device for determining in a simple manner the Radio Compass Coil 11 Turns 4'x 4! Detail Showing Method Reading Compass Card and Correction Scale Standard Compass and Binnacle RADIO DIRECTION FINDER ON LIGHTHOUSE TENDER TULIP DEVELOPED BY BUREAU OF STANDARDS AND BUREAU OF LIGHTHOUSES 312 direction of a radio transmitting station with reference to the point at which the direction finder is located: The direc- tion finder thas a considerable number of very practical applications, of which one of the most important is its use as ati aid to navigation. Sound and visual signaling devices have been employed for many years as aids to navigation. Lighthouses and lightships with their characteristic light flashes and sound signals are established and maintained along the coasts and at harbor entrances in order that shipping may be carried on with maximum safety. During fog or thick weather, however, the sound and visual signaling devices often do not give reliable serv- ice. The radio direction finder is not af- fected by. fog, and has the further ad- vantage that it will operate over, much greater distances than sound and visual signaling devices. Simple Type of Finder The department of commerce has de- veloped a system of. radio direction finding which has proved to be very simple, practical, and dependable. This system has been developed by the bureau. of ‘standards in co-operation with the bureau. of lighthouses. The first in- stallations were made in the third lighthouse district with headquarters at Tompkinsville, N. Y. A common type of direction finder which has been used for ‘installation on shipboard, consists of a coil of 10 turns of insulated copper wire wound on a wooden frame 4 feet square which is mounted so that it may be rotated about a vertical axis. Suitable radio receiving apparatus is used in connection with the coil, and in recent installations has consisted of a variable air condenser for tuning purposes, a balancing con- denser for increasing the accuracy of observed bearings, a 6-tube amplifier having three stages of radio-frequency amplification, a detector, and two stages of audio-frequency amplification, bat- teries, and suitable telephone receivers. As’ the coil is revolved about its verti- cal axis, the intensity of the signal which is being received from the station whose location is to be determined, di- minishes until a minimum is_ reaiched, which occurs when the plane of the coil comes to a position at right angles to the line of direction to the radio transmitting station. At this point of minimum signal, the radio bearing is