<html><head></head><body><div class="ydp6a02a16dyahoo-style-wrap" style="font-family:times new roman, new york, times, serif;font-size:16px;"><div></div>
<div dir="ltr" data-setdir="false"><div><div class="ydp3e7db910yahoo-style-wrap" style="color: rgb(0, 0, 0); font-family: times new roman, new york, times, serif; font-size: 16px;"><div dir="ltr" data-setdir="false">I hear ya River, but given that internal AA batteries considerably attenuate the interference and in some cases eliminates it, I don't think the RG58 cable plays any role with the noise. The only discernable hardware difference between an OTS powered by internal AA batteries and an external battery is the length of wire connecting the battery to the OTS circuitry. For this reason I believe motor controller EMI is inducted into the power cables and is close enough to the resonance of the transducer that it is spilling into the OTS circuitry from the incoming power rails. The relatively short wires connecting internal AA batteries to the OTS unit (4 inches?) induce much less EMI than the long wires of an external battery (8 feet or so in my case) which again, would explain why the noise is considerably reduced or ceases by merely switching to internally located AA batteries.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">For those of us that want to keep using an external battery, an alternative to a faraday cage surrounding the motor controller might be using armored battery cables or running the cable through EMT conduit to help limit interference.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Kittredge's human powered sub is looking better and better, guys. Anybody got a ten-speed and 24 inch prop for sale?</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Jon</div><div dir="ltr" data-setdir="false"><br></div><div><br></div></div><div id="ydp318111dbyahoo_quoted_6361704093" class="ydp318111dbyahoo_quoted" style="color: rgb(0, 0, 0); font-family: times new roman, new york, times, serif; font-size: 16px;"><div style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 13px; color: rgb(38, 40, 42);"><div>On Tuesday, April 29, 2025 at 08:43:24 PM EDT, River Dolfi via Personal_Submersibles <personal_submersibles@psubs.org> wrote:</div><div><br></div><div><br></div><div><div id="ydp318111dbyiv1149230165"><p dir="ltr">I suspect there is a problem with the shield of the transducer cable "floating" with respect to the hull.</p><div><br></div></div></div></div></div></div></div></div><div id="ydp7a25fe0ayahoo_quoted_6268144718" class="ydp7a25fe0ayahoo_quoted"><div style="font-family:'Helvetica Neue', Helvetica, Arial, sans-serif;font-size:13px;color:#26282a;"><div><div class="ydp7a25fe0ayqt1552613844" id="ydp7a25fe0ayqt82551"><br clear="none"></div></div>
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