Which coil is NOT one of the four degaussing coils?

The H coil is not one of the four degaussing coils typically used in military operations. Degaussing coils are designed to neutralize the magnetic field of naval vessels to reduce the risk of magnetic influence mines, and each has a specific function and configuration.

The FP-QP coil, M coil, and FI-QI coil all play a critical role in the degaussing process. The FP-QP coil is used for the forward and quartering magnetic field compensation; the M coil is essential for compensating the ship's magnetic signature due to magnetic variations; and the FI-QI coil serves to correct the field near the bow and on the quarter.

By understanding how each of these coils contributes to the overall effectiveness of a ship's degaussing system, it's evident that the H coil does not fit into this established framework, as it isn't recognized as a standard degaussing coil configuration used in naval procedures. This distinction clarifies why the H coil is the answer to the question regarding which one is not part of the four degaussing coils.