Engineer Port Repair Ship

by United States. War Department

(3) Radio direction finder. Located on the navigating bridge is the ship’s radio direction finder. This instrument receives radio signals and establishes the bearing of the sending station. It consists essentially of a loop antenna for receiving the signals connected to a radio receiver that makes the signals audible. The position of the ship may be determined from radio bearings by taking cross bearings on two or more stations, by two bearings on the same station and the distance run between bearings, and by a bearing and a sounding.

(4) Fathometer.

(a) A fathometer is installed on the navigating bridge to determine the depth of water under the ship. This instrument works on the echo depth-finding process. Briefly, it consists of a submarine oscillator in the bottom of the ship that produces a sound of sufficient intensity to travel to the ocean floor and reflect back to a sensitive receiver also located in the ship’s bottom. The difference between the time of sending the sound and receiving the echo is measured by the fathometer, translated into depth, and flashed on the dial as a red light opposite a numeral corresponding to the depth in fathoms.

(b) Near the fathometer is a fathometer recorder that records on a paper chart the depths indicated by the fathometer. This gives a continuous depth profile of the ocean bottom along the ship’s course.

(5) Chartroom equipment. In the chartroom are sextants, protractors, dividers, parallel rules, chronometer, hydrographic charts, and a chart table.

c. Communications.

(1) Radio. The radio equipment consists of a main receiver and transmitter with emergency sets and a short-wave receiver and transmitter. The radio sets presently used are shown in figures 9 and 11. The manuals describing this equipment are listed in ASF Catalog Sig 10-1.

(2) Radio telephone. Radio telephone communication is handled by the short-wave transmitter and receiver. (See fig. [11].) They operate on frequencies between 2 and 3 million cycles per second with separate channels designated for specific purposes. For ship-to-shore communication, frequencies range between 2,100 and 2,200 kilocycles. Direct ship-to-ship communication is on 2,738 kilocycles. The sets thus send and receive on different frequencies.

(3) Visual signal equipment.