T3PLLä38

Technical Page 1

              Directly to the right of the door on entering the radio room is the radio direction finder and low frequency radio receiver. (Click to see photo 1.) It is nineteen inches high, nine inches deep, and fourteen inches wide. (Click to see photo 2.) It is made by Telefunken, type T3PLLä38, and employs an external power supply. (Click to see drawing 1.) This receiver is secured to the bulkhead above the shelf built around the room, which serves as a table. Directly in front of the receiver, the table top has a window about twelve inches square built into it. (Click to see photo 3.) Under the table is the loop rotating control. It is quite conventional except that in addition to the ordinary relative bearing scale, a gyro repeater is mounted coaxially with the wheel enabling true or relative bearings to be read directly by looking through the window.

              The receiver has five positions on the band selector switch covering the following frequencies:

                                         Band I                 70 – 150 kHz

                                         Band II               150 – 350 kHz

                                         Band III              350 – 640 kHz

                                         Band IV             640 – 1200 kHz

                                         Band V                15 – 33 kHz

              This receiver was used as a low frequency communications receiver in addition to being used for direction finding.

              The receiver was tried out and seemed to have excellent sensitivity on all bands. An attempt to take a bearing was made but no null could be found. The sense antenna lead, which led to the transmitter patch panel, consisted of what looked like 70 ohm coaxial cable. This is considered extremely poor practice in the U. S. Navy and undoubtedly is one reason no bearings could be taken. All antennas were patched in and no change was noted.

              The loop antenna (Click to see Drawing 2) is a little over thirty inches in diameter and retracts by means of compressed air into the starboard superstructure just forward of the captain’s station. It is mechanically coupled to the wheel in the radio room by drive shafts, differentials, and flexible couplings. (Click to see Drawing 3).

              The direction finder unit is equipped with a meter and built-in test switch, with nine positions to enable rapid checking. (Click to see Photo 4).

              The tube lineup consisted of three Telefunken RES094 tubes and three Telefunken RE084K tubes. (Click to see Equip. Description).