LF/MF Communications Equipment Aboard USS Ling (SS-297) - Part 4

By Howard F. Holden WB2AWQ

Part 1 LF & MF Communications Equipment Aboard USS Ling (SS-297)

Part 2 LF & MF Communications Equipment Aboard USS Ling (SS-297)

Part 3 LF & MF Communications Equipment Aboard USS Ling (SS-297)

These hatches are about 20 inches wide, 36 inches tall, rounded at top and bottom. The transmitter is constructed as a two-piece unit, splitting vertically. It may indeed fit through the hatches, but I am wondering WHO they got to actually lift that beast once it was inside the very cramped quarters of the submarine!

The Ling's TBL is presently not operational because it is powered from a motor-generator set that runs off the sub's 230 VDC battery buss.  The condition of the buss is unknown at this time, and the motor draws some 50A at startup, which means we would have to provide some fancy rectified 220V AC down there.

Before applying any power, we will also have to prove out all of the HV lines with a megger to ensure they are safe after 55 years. The generator provides 2000VDC, 1000VDC, and 77V AC to the TBL. Restoration of the TBL is still some time away, although cursory examinations of its interior show it to be in excellent condition.

From the tuning setting cards found on the equipment the following frequencies below 535 kHz were in use:

• 500 kHz TX and RX old international distress and calling frequency

• 450 kHz TX and RX

• 434 kHz TX and RX

• 422 kHz TX only

• 355 kHz TX and RX

• 194 kHz RX only (call letters TUK listed, location unknown.)

• 190 kHz RX only ( call letters NMF listed, this frequency is the US Coast Guard, Boston MA)

The TX and RX frequency pairs other than 500 kHz are probably Navy simplex working frequencies, while the TX only and RX only frequencies, except 190 kHz, are probably commercial station frequencies. Typically, the Navy used single frequencies for CW traffic, while com-mercial stations used split frequencies for full break-in operation. The information found on the sub is very scanty. We have not located any radio logs, and the deck logs don't list actual frequencies or shore stations used, nor do we know what time period or stations, other than TUK and NMF, the equipment setting cards represent.

One very essential piece of equipment required to operate both the TBL transmitter and the RAK and RAL receivers is the LM-18 heterodyne frequency meter. The LM-18 is similar in operation to the more common BC-221 Army frequency meter.