[PSUBS-MAILIST] OTS and motor controller noise

[Jon Wallace via Personal_Submersibles]

 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.
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.
Kittredge's human powered sub is looking better and better, guys.  Anybody got a ten-speed and 24 inch prop for sale?
Jon

On Tuesday, April 29, 2025 at 08:43:24 PM EDT, River Dolfi via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


I suspect there is a problem with the shield of the transducer cable "floating" with respect to the hull.


  
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