Radio Operations Aboard Submarines

By Robert E. Straub - KC2AIO <>

Receivers & Misc. Equipment in Submarine Radio Room


     The main receivers aboard submarines were the RAK/RAL combination. Both receivers were identical in appearance, with the difference being in the tuning range. Their physical size was approximately a 15 inch cube, as were their respective power supplies. The units were designed to operate from the submarine's 115 volt, 60 cycle AC supply lines or in the case of an emergency they could be supplied power by the submarine's batteries. The RAK/RAL's were manufactured by the Radio Corporation of America


RAK - 15 to 600 kcs

RAL - 300 to 23,000 kcs.

     Neither receiver had a calibrated tuning dial. The use of a separate frequency standard was used to set the desired frequency. This frequency standard, known as the LM Frequency Meter, provided an accurately calibrated and stable radio frequency. The LM Frequency Meter was also used in calibrating the TBL transmitter. A calibration chart would supply information for the desired operating frequency, and this signal would be used to tune the transmitter and receivers. The LM was designed by the Bendix Corporation.

     Another long and short wave radio, the RBO, manufactured by Scott Company, was used for entertainment and the collecting of news. A daily newspaper was issued early each morning. (I do not know if this practice was wide spread among all submarines).

     Another piece of equipment, the TOP SECRET ECM (Electronic Coding Machine and I'm not aware of a model number) was located in a locked safe inside the radio room. Only officers were allowed access to this machine when encoding or decoding radio messages.

     The remaining radio related equipment in the Radio Room would be the straight key, mounted on the desk top, the manual typewriter with all capital letters, and the antenna connectors exiting from the antenna trunk located in the overhead of the Radio Room.

     The antenna system consisted of three long wire antennas located topside.

     Two of the antennas were located on either side of the conning tower shears and the third was located up in the periscope shears and ran aft to the stern of the submarine.

     This pretty well encompasses the radio equipment in the radio room. However, there were also radar units (power supplies etc.) in the room, so that did not allow very much space in a 5 x 8 foot room for the operator.

     The RAK/RAL receivers were TRF (tuned radio frequency). The tuned radio frequency stages were followed by a superregenative detector and audio stages.

     Headphones were used most of the time.

     Later in WWII - late in 1944 or early 1945 - the RAK/RAL combination was replaced with two identical RBS superhet receivers, giving the same frequency coverage as the RAK/RAL combo. These new receivers were manufactured by RCA.

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