Hey everyone,
Thought I'd toss in my $.05 here. I work in Naval Aviation and have to deal with lots and lots of wiring. All of you have hit on major points, the foil acting as an EMI shield for each lead of wire and acting as a common ground.
For an example... In a RADAR system, the radio frequency data is carried on a coaxial (cable tv style) cable, with a core wire for the data and two shields, one is a ground the second is the EMI shield.
As a suggestion, if possible, use a small gage coaxial cable to take the place of the wire and its foil shield. The shield of the cable can be connected to the ground lead at the connector and this will maintain the EMI shielding and the fidelity of the data being transmitted.
Hope this helps,
AT1(AW/SW) Benjamin T. Fritz, USN
CNATTU Jacksonville, FL
P-3C Schoolhouse, Avionics
--- On Tue, 3/16/10, David Bartsch <dbartsch2236@hotmail.com> wrote:
From: David Bartsch <dbartsch2236@hotmail.com>
Subject: RE: [PSUBS-MAILIST] forward scan sonar answer
To: personal_submersibles@psubs.org
Date: Tuesday, March 16, 2010, 9:17 PM
Alec, My big issue with plugs is these too are not shielded...perhaps some foil around individual crimp connections? Let me play with this
some... David Bartsch
Subject: RE: [PSUBS-MAILIST] forward scan sonar answer Date: Tue, 16 Mar 2010 20:19:11 -0400 From: Alec.Smyth@compuware.com To: personal_submersibles@psubs.org
Thanks David. I believe what is normally done is to send the shielding through one of the pins on the hull penetrator. However, in this case there's a whole bunch of these foil wrappings. I think I attempted to send one of them, on the theory they were not isolated from each other. Or were they isolated? I can't recall.
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From: owner-personal_submersibles@psubs.org on behalf of David Bartsch
Sent: Tue 3/16/2010 5:56 PM
To: personal_submersibles@psubs.org
Subject: [PSUBS-MAILIST] forward scan sonar answer
Alec, I have the solution already about your forward scanning sonar. If you opened and separated the individual wires within the cable for this sonar unit, you will notice that these are individually wrapped in foil. One wire is not covered with an isolative plastic...this is to say it is exposed. This foil that shrouds each wire aids in isolating them one from another to prevent emi as individual wires transmit a short duration strong signal. This electro magnetic interference is sent down this foil and returns from each wire back into this exposed wire which serves as a common ground. When you severed this cable to install this SEACOM thru hull fitting, these wires are properly insulated but lack any shield. Once within the hull, again, these wires are insulated but are susceptible to emi having no shield. The length of this unprotected
cable run is about three feet. Large spike signals in any wire will send noise down all the surrounding wires and give you this interference you see on your screen. Solution: This is at this point theoretical but make good sense... give me time to reinstall the cable to itself omitting this thru hull to first verify this system still fully function (I feel I can fix this) then, once the system if again fully working as it should, we perhaps as a group can devise a way to produce a thru hull connection that will not omit this very needed wire isolating shielding. In this way you could have this unit installed aboard your sub in working and hence usefull
form. David Bartsch
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