Specifications

BATS AND PORTABLE BATS OPERATION
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3. Check that hydrophone shaft is not strumming or vibrating excessively. This causes excess
noise at hydrophone. If pole is strumming, change configuration (shorten the shaft, but
watch out for reflections) or add fairing to shaft.
3.6.2 ACOUSTIC PROBLEMS IN RESPONDER MODE
A responder replies acoustically to an electrical interrogation pulse from the transceiver. Like a
transponder, a responder provides the timing information needed to measure horizontal range di-
rectly, but the interrogation pulse is not subject to the acoustic interference associated with a tran-
sponder. However, because a responder must be electrically connected to the tracking system, it
may not be a feasible option for some operations.
When operating in the responder mode, multi-path interference is limited to cases where the direct
arrival of the acoustic reply is blocked or reflected.
If this occurs, it may be necessary to reconfigure the system so that the hydrophone is in a posi-
tion to receive the direct signal. For example, the hydrophone may not be mounted far enough be-
low the ship's keel to receive a direct signal from a responder on the other side of the ship.
Avoid an operation where a towfish is tracked behind the vessel near the water surface, so that the
direct signal from the beacon is reflected or attenuated by the ship's wake. Either tow the fish off-
center, out of the ship's wake, or sink the responder below the wake.
When operating in and around subsea structures, there is always a number of locations where
there is no direct path between the responder and the hydrophone, and the operator should expect
occasional multi-path interference in these situations.