Radio Operations Aboard Submarines

By Robert E. Straub - KC2AIO <>


     Submarines were equipped with both active and passive sonar gear. The QC/JK gear was located in the Conning Tower. These were companion units with the QC gear being the active and passive sonar and the JK gear was the passive sonar only. Both sonars were manned when the submarine was submerged. A large bearing indicator, for both the QC and JK sonars, indicated the relative position to the submarine's bow of the sound head bearing. The QC sonar had the "pinging" capability, but was rarely, if ever, used due to compromising the submarine's position. The sound heads were raised. lowered and trained from the operating positions in the Conning Tower. The raising and lowering was done by a hydraulic system and the training was done by an electric motor controlled by a handle at the operating station for both the QC and JK sonars. The lowering and raising mechanism for the two sound heads was located at the after end of the forward torpedo room. This allowed the sound heads to be raised inside a protective well when the submarine was on the surface.

    The QC sonar was equipped with a straight key and CW could be used for emergency or identifying purposes.

     Normally headphones were worn by the sonar operators. However, speakers were available.


     The Fathometer, located in the Control Room, was used to measure the depth of the water from the submarine's keel to the ocean floor. A "ping" would be sent out and the time delay in receiving the return echo would establish the depth of the water. Again, for security and safety purposes this was rarely used. I know of only one occasion that a single "ping" was used for measuring the depth of the water.


     The JP Sonar gear, passive only, was located in the Forward Torpedo Room and its associated hydrophone was located directly overhead on the main deck. The hydrophone was coupled to the unit by means of a shaft, gear and a crank handle.

    Rotation of the hydrophone was strictly by man power. With the hydrophone being located topside it allowed the submarine to "hear" when sitting on the ocean floor.

    The sonar operators were trained to fire a special acoustic torpedo with this JP gear.

     Late during WWII the JP sonar was replaced with the JT version. This used a larger hydrophone and the training mechanism was improved from the manual operation to a electrical/hydraulic system.

     NOTE: I'm not sure of the designers of this sonar equipment, but I do believe that it was the Underwater Lab at New London, which I also believe has changed its name.

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