This paper presents a continuation of the passive range measurement efforts reported at the 90th conference. Previous work included the modeling of passive range determination using a single point receiver based on moving source observables. The outcome as reported last year was a parameterization of a hypothetical system that had the capability to determine range to source passively. This year, we have expanded the work to include building a fully operational system and field testing it against various moving sources. In addition, a pseudo‐Fourier analysis section has been incorporated to accurately and correctly sort out and classify moving sources. This, coupled witha prioriselection information coded into the system, enables it to perform those required functions against preselected sources while ignoring nondesired signals. We have concentrated this year on enlarging our data base of acoustic signatures with an eye to determining the points of commonality between major source classes. This has led to vastly simplified signal processing techniques compared with previously tried methods. Specifically, we have found that within a source class, certain fundamental signature components cannot be masked by purely physical means without materially degrading the operation of the source. Masking efforts employing jamming techniques are not as effective as desired, since jamming means that the total acoustic output has been raised yielding a more visible source. Baffling of noise sources, while effective for high‐frequency noise components, tends to be less than effective when used to suppress the lower components without an attendant loss in source mobility performance.