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RE: [PSUBS-MAILIST] Passive sonar
Sean,
I'm not sure what this type of cable is called, but it's certainly not coax. Although the conductors are individually wrapped, there is no mesh or shield around the whole assembly, just the neoprene jacket. So that brings up an idea. Presumably I could get some sort of mesh and insert the cable into it, then ground it to the hull. D'you think it worth doing, and if so should I do both inside and outside, or is it fair to expect most noise is constrained to the interior of the sub? On the outside, the cable is not running too close to anything like thrusters. Inside the hull, there must be all kinds of noise.
By the way, I kept the original length of the cable, in case that would have some effect on the sonar - I even cut out the same length of cable as was added by the penetrator. So there's quite a coil in the sub. D'you think this is necessary? I may actually be picking up more noise that way, and if I can get rid of the surplus, it'll be a little neater.
Thanks,
Alec
-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Sean T. Stevenson
Sent: Tuesday, September 18, 2007 1:21 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] Passive sonar
Alec - what signal / wire type is the cable from your sonar (i.e. twisted pair, coax, etc.)? In the case of RF signals carried on coax, it is often important to match the impedance of the cable / fittings to the device. As for shielding, more is generally better, but common-mode noise rejection is typically taken care of by the outer braid/shield. Make sure that you connect that one to one end of the cable assembly only. Connecting chassis ground to chassis ground on both ends can introduce ground loop problems. If the shield is connected to the sonar case, you want it to run the entire length of the cable (through your connector), but not connect to ground through the chassis of your receiver.
Alternately, if the shield does not make any chassis connection on the transducer end, you can connect it to chassis on the receiver end only. As for the individual conductor shields, it is not necessary to connect these electrically through your connector. The idea is that the outer braid / shield performs ambient noise rejection - the individual shields really just reduce crosstalk between conductors, or in some cases reject frequency content in ambient noise that is not adequately attenuated by the outer shield due to its construction (i.e. braided outer shield with less than 100% coverage, but solid foil individual shields. Ideally a connector would be metal (shielded), but isolated electrically from the hull, and the outer shield would connect through it and not a pin in the connector. In the case of plastic or composite connectors, you can use a pin. A typical standard is to use pin 1 for signal ground / common, pin 2 for power, and the last pin on the connector for chassis ground / shield / drain.
Connectors with gold plated contacts are recommended for low-level (unamplified) signals. The gold acts to reduce corrosion on the contact surface, but also is soft and so allows for maximum electrical contact between pin and socket.
-Sean
Quoting "Smyth, Alec" <Alec.Smyth@compuware.com>:
> This hits right on one of my unresolved nuisances. I have an
> InterphaseVista sonar in my K-250. The product manual has dire
> warnings about cutting the cable to the transducer, but I wasn't
> comfortable putting the cable through a compression gland into the
> hull. So I went ahead and cut it on the basis that I'd rather risk the instrument's performance than the integrity of the hull.
> I used a Subconn bulkhead connector, and had the intention of putting
> the shielding through the penetrator by using one of the pins for that purpose.
> However, I found it impossible to do because of how the cable was
> constructed. Each of the conductors had it's own shielding, but
> they're incredibly flimsy tin foil thingies that all unravel and break
> up. The penetrator itself is not shielded, it's all plastic besides the pins.
>
> The result is that the depth sounder reading on the instrument works
> fine, but the forward looking sonar image does not correspond to
> what's actually in the water. It doesn't actually look like electrical
> noise on the screen, but I think that's just because the screen
> refreshes only periodically. The sonar image looks proper, but it just isn't what's out in front of the sub.
>
> Any suggestions would be most welcome. Perhaps a different kind of
> penetrator?
>
>
> thanks,
>
> Alec
>
>
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> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org] On Behalf Of
> cbussel@comcast.net
> Sent: Monday, September 17, 2007 8:03 PM
> To: personal_submersibles@psubs.org; personal_submersibles@psubs.org
> Cc: Stephen Pearce; 'David Bartsch'
> Subject: RE: [PSUBS-MAILIST] Passive sonar
>
>
> Steve,
> If you are looking for a simple gland, as long as your cable is water
> blocked, you can purchase stainless steal ones from McMaster-Carr. I
> have used the ones from McMaster on pressure balanced oil-filled
> (PBOF) housings down to 1000 meters. The cable has to be water blocked
> though. You can purchase water blocked cable from Impules, Subconn,
> our any connector manufacture. Falmat cable company makes the water
> blocked umbilcals for numerous ROV companies, they might have some in
> stock to purchase a short piece.
> If your gland in coming directly into your sub, I would recommend a
> bulk head connector, unless they are pressure compensated, most will
> leak at or below 80 psi.
> Hope this helps,
>
> --
> Craig Bussel
>
>
>
> -------------- Original message --------------
> From: "Stephen Pearce" <sjpearceqld@bigpond.com>
>
>
> G-day everyone
>
>
>
> Does anyone one in the group have any information on what type of
> through hull glands are used for video coaxial and power cables like
> those used on ROV's or maybe subs owned buy group members?
>
>
>
> Are there any good suppliers that any members know about?
>
>
>
> Any help will be appreciated!
>
>
>
> Regards
>
>
>
> Steve Pearce
>
>
>
> -----Original Message-----
> From: David Bartsch [mailto:dbartsch2236@hotmail.com]
> Sent: Tuesday, 18 September 2007 8:34 AM
> To: sjpearceqld@bigpond.com
> Subject: FW: [PSUBS-MAILIST] Passive sonar
>
>
>
>
>
> > Date: Mon, 17 Sep 2007 09:38:22 -0700
> > From: ronleonard@shaw.ca
> > Subject: RE: [PSUBS-MAILIST] Passive sonar
> > To: personal_submersibles@psubs.org
> >
> > Try these:
> >
> >
> http://www.ancorproducts.com/scpt/SectionPage.php?loadSubs=Ancor_WIRE%20MANA
> > GEMENT%20PRODUCTS_WIRE%20SEALS
> >
> > Good to 300'
> >
> > Ron
> >
> > -----Original Message-----
> > From: owner-personal_submersibles@psubs.org
> > [mailto:owner-personal_submersibles@psubs.org] On Behalf Of David Bartsch
> > Sent: Monday, September 17, 2007 6:18 AM
> > To: personal_submersibles@psubs.org
> > Subject: Re: [PSUBS-MAILIST] Passive sonar
> >
> > Peter,
> >
> > I have reestablished the omni dirrectional option to the sonar. It was !
> > ; one of those very simple problems that was so easy to solve, I
> could not see
> >
> > the answer.
> >
> >
> >
> > David Bartsch
> > P.S.: The flooding took place at the point in which the hydrophone
> interface
> >
> > cable entered the hydrophone. We will be patient and give Stephen
> some time
> > to work it over and hopefully redesign it.
> >
> >
> > >From: "David Bartsch" <dbartsch2236@hotmail.com>
> > >Reply-To: personal_submersibles@psubs.org
> > >To: personal_submersibles@psubs.org
> > >Subject: Re: [PSUBS-MAILIST] Passive sonar
> > >Date: Mon, 17 Sep 2007 08:15:28 -0400
> > >
> > >Peter,
> > >
> > > Stephen Pearce is working on an upgrade to the hydrophones...It
> is only
>
> > >good now to 40 FSW! He tested it in a pressure tank and it started
> flooding
> >
> > >at 18psi. Good to know thow.
> > >
> > >
> >
> >! ; > David Bartsch
> > >
> > >
> > >
> > >
> > >>From: "Peter Madsen" <peter@submarines.dk>
> > >>Reply-To: personal_submersibles@psubs.org
> > >>To: <personal_submersibles@psubs.org>
> > >>Subject: Re: [PSUBS-MAILIST] Passive sonar
> > >>Date: Mon, 17 Sep 2007 09:35:51 +0200
> > >>
> > >>
> > >>Hi,
> > >>
> > >>I really hope for your sucses !
> > >>
> > >>Peter Madsen / UC-3 Nautilus
> > >>
> > >>----- Original Message ----- From: "David Bartsch"
> > >><dbartsch2236@hotmail.com>
> > >>To: <personal_submersibles@psubs.org>
> > >>Sent: Monday, September 17, 2007 5:57 AM
> > >>Subject: [PSUBS-MAILIST] Passive sonar
> > >>
> > >>
> > >>>PSUBS,
> > >>>
> > >>> The passive sonar I have been working! on for so long is completed!
> The
> >
> > >>>omni dirrectional mode was ommitted as problems existed with
> this mode on
> >
> > >>>initiall installation.
> > >>> Testing aboard a small pleasure craft will be conducted during the
> > >>>Spring of 2008. Although trainable search mode is operational, I must
> > >>>determine the exact cone of geographical coverage of each
> hydrophone so
>
> > >>>as to avoid "gaps" of contact detections between hydrophones.
> > >>> In shop testing proved very good with the selected hydrophones
> > >>>"active" once selected.
> > >>> The premp/amp console has "extra" jack inputs for cavitation and
> > >>>other own ship noise monitoring purposes.
> > >>> We are on our way!
> > >>>
> > >>>
> > >>>David Bartsch
> > >>>
> > >>>_________________! _______ _________________________________________
> > >>>Gear up for Halo® 3 with free downloads and an exclusive offer.
> > >>>http://gethalo3gear.com?ocid=SeptemberWLHalo3_MSNHMTxt_1
> > >>>
> > >>>
> > >>>
> > >>>
> >
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