[PSUBS-MAILIST] OTS

Sun Oct 25 07:12:05 EDT 2020

David,
If you look at commercially used underwater acoustic equipment, lots of
them incorporate protection for the delicate transducer. The two most
common methods I've seen have been a cage welded together from bent
stainless steel rod, or a guard made from a thick walled tube of delrin
plastic with the transducer inside pointing out the open end.
Does anyone know what the beam pattern for the OTS transducers is? I would
imagine that it's hemispherical, but the story about losing comms with R300
as it got laterally farther from the boat makes me think that it might be a
narrower pattern.
Thanks,

-River J. Dolfi

rdolfi7 at gmail.com

On Sun, Oct 25, 2020 at 12:57 AM via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

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>    1. Re: OTS (David Colombo via Personal_Submersibles)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 24 Oct 2020 21:56:42 -0700
> From: David Colombo via Personal_Submersibles
>         <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion
>         <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] OTS
> Message-ID:
>         <CAHHFyEG=U=R4tu0pqfEnqEYMRXGgnzbpsNZ-bn+KAbriFzUa=
> A at mail.gmail.com>
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>
> Sean, thanks that is what I was thinking as im sitting here playing with a
> piece of the coax. In the mounting of the transducer and the retention
> ring, am using a silicone fill around the lower portion of the retention
> bracket to hold it in place so that its not connected rigid  to the hull.
> As the diver unit transducer is a bit smaller diameter than the transducer
> on the topside unit. I am thinking a sheild around the transducer maybe
> made of acrylic to protect against impact to the transducer. It would sit
> away from the transducer.  Do you have any concerns about this with it
> ability to receive signal?
> David
>
> On Sat, Oct 24, 2020, 9:37 PM Sean T. Stevenson via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> > David, with coax, it's better if you loosen and pull the shield braid
> back
> > over the jacket all around on both sides, then cut the core wires a bit
> > shorter. Solder the cores together and insulate, then pull the braid back
> > into position with full 360? coverage, and twist it into the braid from
> the
> > other side - cutting the cores shorter should have given you a bit of
> > overlap to work with. Solder the braid all around and then heat shrink
> the
> > works.
> >
> > Sean
> > -------- Original Message --------
> > On Oct. 24, 2020, 22:09, David Colombo via Personal_Submersibles <
> > personal_submersibles at psubs.org> wrote:
> >
> >
> > Rick, I am cutting the ots comms wire as well to shorten its lenght for
> > the yellow sub, and to get it thru the blue globe fittings. Attached are
> > photos of the shield which is a braided multi strand wire and the
> interior
> > wire which is also multi strand.  I am assuming that when i rejoin the
> two
> > pieces there might be a small gap in which the sheilded braid may not
> > completely cover the inner core.  Its kinda like a chinese finger braid
> > that tightens when pulled on the ends. Does anyone have any concerns
> about
> > the surrounding sheild braid not completely covering the inner core?
> > Since the cable is 50ft long, I have lots of lenght to play with.
> > David
> >
> >
> > On Sat, Oct 24, 2020, 5:51 PM Rick Patton via Personal_Submersibles <
> > personal_submersibles at psubs.org> wrote:
> >
> >> Yeah I have the surface head set system so should be fine. I had to cut
> >> the wire though to pass it threw the hull penitraitor so I hope it will
> be
> >> easy to re connect and not have any shielding leaks from any other stuff
> >> running.
> >>
> >> On Sat, Oct 24, 2020 at 10:54 AM Sean T. Stevenson via
> >> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> >>
> >>> I think the boom mics on the surface headsets are pretty forgiving. The
> >>> issue with the diver mics is that they are of a noise canceling
> design. In
> >>> an effort to filter out regulator hiss and bubble noise, there are
> >>> diaphragms on both sides of the mic, and the transmitted signal is
> actually
> >>> the differential between the two, which is best when the mic is right
> in
> >>> front of the diver's mouth. A lot of divers find this position a bit
> >>> invasive and incorrectly push it away further into the mask cavity, so
> then
> >>> the mic is exposed to similar signals on both sides and becomes less
> >>> intelligible.
> >>>
> >>> Not an issue for the surface hand mics or headsets.
> >>>
> >>> Good idea with the transducer mounting. High and omnidirectional is
> >>> ideal, so you avoid the shadowing. Actually, this is one area where
> OTS has
> >>> a deficiency in comparison to one of its competitors, at least with the
> >>> diver units. The SSB-2010 needs to be mounted on a waist belt, or on a
> tank
> >>> cam band, and there's really no practical mounting position for that
> unit
> >>> that leaves the transducer in an optimal position. Even the low powered
> >>> Buddy Phone units that they sell for recreational divers are mounted
> on the
> >>> side of the head, and exhibit shadowing in the cross body direction. In
> >>> contrast, Divelink makes their diver worn units with transducers that
> sit
> >>> on top of the head, attached to the upper strap of the face mask. I'm
> still
> >>> inclined to buy OTS though. On a sub of course, you can mount your
> >>> transducer anywhere you like.
> >>>
> >>> Sean
> >>>
> >>>
> >>> -------- Original Message --------
> >>> On Oct. 24, 2020, 14:33, Rick Patton via Personal_Submersibles <
> >>> personal_submersibles at psubs.org> wrote:
> >>>
> >>>
> >>> Thanks Guys
> >>>
> >>> In my case, the surface boat will not have the need to be underweight,
> I
> >>> will descend from the surface boat and it will just stay put except for
> >>> moving with the current. I won't have the thermoclines here in Hawaii
> that
> >>> most of you have but there are some of course. I will be using a
> headset
> >>> with boom mike so it will be almost touching my lips and I mounted the
> >>> transducer on the top of my hatch to minimize any ghosting on my end. I
> >>> agree Jon that it would be nice to have a topic on that. I would like
> to
> >>> put a face with all the guys here so where and when will be the next
> >>> convention? Oh yeah, the bloody coronavirus.Just got my trailer done
> enough
> >>> to get it weighed and a VIN number assigned to it so am stoked!
> >>> Rick
> >>>
> >>> On Sat, Oct 24, 2020 at 9:26 AM Jon Wallace via Personal_Submersibles <
> >>> personal_submersibles at psubs.org> wrote:
> >>>
> >>>> My recollection from Lake Tahoe was that comms were good when surface
> >>>> boat was somewhere in the vicinity OVER the submarine.  We didn't
> have to
> >>>> be directly overhead, just not too far away.  When David piloted
> R-300 he
> >>>> ended up a good 600-800 feet away from us laterally when comms became
> >>>> difficult.  Water column varied 60-100 feet (I think) in that area.
> Comms
> >>>> ended when our propeller cut the transducer cable (whoops), ALWAYS
> pull up
> >>>> the transducer when surface boat is underway, even at slow speeds.
> I'm
> >>>> just going to throw out a rule of thumb that has no emperical data to
> back
> >>>> it up, keep within the same distance laterally as the submarine is in
> >>>> depth.  If the sub is 100 feet deep, stay within a 100 foot radius of
> it.
> >>>> If it's at 1000 feet depth, stay within 1000 foot radius of it.  I
> think
> >>>> you could actually probably get away with a radius 4x depth and be
> ok, but
> >>>> keeping it 1-to-1 isn't a bad plan.
> >>>>
> >>>> Sean is correct that water conditions matter as well as fresh vs salt.
> >>>> Even so, we should spend some time at our next "meet" to do some comm
> >>>> testing and publish the results on the web site just so we have some
> >>>> reference.
> >>>>
> >>>> Notwithstanding the timber sound aesthetics Sean mentioned, comm
> >>>> quality between surface and R-300 was loud and clear when within the
> >>>> parameters I mentioned above.  Cliff and David may have their own
> >>>> perceptions since they both manned the comms at some point during that
> >>>> weekend.
> >>>>
> >>>> Jon
> >>>>
> >>>>
> >>>>
> >>>> On Saturday, October 24, 2020, 03:01:32 PM EDT, Sean T. Stevenson via
> >>>> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> >>>>
> >>>>
> >>>> Rick, ultrasound behaves quite a bit different than does radio as far
> >>>> as the attenuation relationship to distance. Things like shadowing,
> (where
> >>>> a diver's body / equipment or the hull or superstructure of your sub
> gets
> >>>> in between the direct line of sight between transducers) will have a
> much
> >>>> more profound affect on transmission effectiveness than distance
> alone.
> >>>> Similarly, thermoclines and haloclines can act as "surfaces" that
> refract
> >>>> or reflect the ultrasonic transmission, so it is important for the
> surface
> >>>> crew to lower their transducer into the same operating layer as the
> diver /
> >>>> sub. As a diver, I always report the presence and depth of any
> thermocline
> >>>> encountered on descent to the surface support for this reason. Also,
> the
> >>>> surface transducer needs to be suspended in the water column and not
> >>>> bottomed or lost in surface sea clutter, and the transducer needs to
> be
> >>>> weighted and boat speed limited so that it doesn't trail behind at an
> angle
> >>>> which is ineffective for transmission.
> >>>>
> >>>> The rating in the published specifications for the OTS SSB-2010 (a 5
> >>>> Watt unit) is greater than 1000 meters in a calm sea, and ~200 meters
> in
> >>>> sea state 6 (Beaufort), but I presume that these are ideal scenarios
> >>>> whereby the surface and dived transducers are suspended at the same
> depth,
> >>>> in the same (vertical) orientation, with clear line of sight and no
> >>>> interfering reflections, and also with no squelch applied. Real-world
> >>>> conditions are obviously somewhat different, and the environment can
> >>>> actually be somewhat noisy at typical channel frequencies, requiring
> the
> >>>> application of some squelch and the consequent loss of range.
> >>>>
> >>>> Rated frequency response is ~300 Hz to ~3000 Hz, which covers most of
> >>>> the vocal range, but will not reproduce true timbre of voice. It is
> fine
> >>>> for intelligible speech, but not for e.g. music.
> >>>>
> >>>> I have used this unit as a diver only, so my impression may be also
> due
> >>>> to the influence of the earphone / microphone assembly in my mask.
> Choice
> >>>> of mask makes a difference (shape and size of gas cavity), as does
> >>>> proximity to the mic. You need to be almost kissing those OTS diver
> mics to
> >>>> get decent sound. That said, my experience with the SSB-2010 was
> decent,
> >>>> but that was in the context of a dive team separated by a few meters
> at
> >>>> most, and at relatively shallow depths (limited distance from surface
> unit)
> >>>> where helium based breathing gas was not required.
> >>>>
> >>>> I can't speak to long range effectiveness, other than at Flathead last
> >>>> year I was surface support for Cliff in the R-300. He was using a
> SSB-2010,
> >>>> but the surface unit we had was something different - one of the
> surface
> >>>> specific boxes, and I don't recall the model (Cliff?). There were
> times at
> >>>> which we lost him and had to reposition the boat to reacquire him, and
> >>>> others where we could hear him but he couldn't hear us, but I can't
> speak
> >>>> to the exact ranges, depths or boat speeds that caused those issues.
> It was
> >>>> never such a sustained loss of comms that the dive had to be called.
> Likely
> >>>> the result of relative orientation or depth, or shadowing of the
> >>>> transducers.
> >>>>
> >>>> Sean
> >>>>
> >>>>
> >>>>
> >>>> -------- Original Message --------
> >>>> On Oct. 24, 2020, 12:10, Rick Patton via Personal_Submersibles <
> >>>> personal_submersibles at psubs.org> wrote:
> >>>>
> >>>>
> >>>> wanted to hear from those who have and have used the OTS comms system.
> >>>> I was wondering how you liked the system and what your max clear
> >>>> audible range was.
> >>>> Thanks
> >>>> Rick
> >>>>
> >>>> _______________________________________________
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