<div dir="ltr"><div dir="ltr">David,</div><div dir="ltr">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.</div><div dir="ltr">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.<br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Thanks,</div><div><br></div><div dir="ltr">-River J. Dolfi<div><div><br></div><div><a href="mailto:rdolfi7@gmail.com" target="_blank">rdolfi7@gmail.com</a></div></div></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Oct 25, 2020 at 12:57 AM via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Send Personal_Submersibles mailing list submissions to<br>
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1. Re: OTS (David Colombo via Personal_Submersibles)<br>
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Message: 1<br>
Date: Sat, 24 Oct 2020 21:56:42 -0700<br>
From: David Colombo via Personal_Submersibles<br>
<<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>><br>
To: Personal Submersibles General Discussion<br>
<<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>><br>
Subject: Re: [PSUBS-MAILIST] OTS<br>
Message-ID:<br>
<CAHHFyEG=U=R4tu0pqfEnqEYMRXGgnzbpsNZ-bn+KAbriFzUa=<a href="mailto:A@mail.gmail.com" target="_blank">A@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="utf-8"<br>
<br>
Sean, thanks that is what I was thinking as im sitting here playing with a<br>
piece of the coax. In the mounting of the transducer and the retention<br>
ring, am using a silicone fill around the lower portion of the retention<br>
bracket to hold it in place so that its not connected rigid to the hull.<br>
As the diver unit transducer is a bit smaller diameter than the transducer<br>
on the topside unit. I am thinking a sheild around the transducer maybe<br>
made of acrylic to protect against impact to the transducer. It would sit<br>
away from the transducer. Do you have any concerns about this with it<br>
ability to receive signal?<br>
David<br>
<br>
On Sat, Oct 24, 2020, 9:37 PM Sean T. Stevenson via Personal_Submersibles <<br>
<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
<br>
> David, with coax, it's better if you loosen and pull the shield braid back<br>
> over the jacket all around on both sides, then cut the core wires a bit<br>
> shorter. Solder the cores together and insulate, then pull the braid back<br>
> into position with full 360? coverage, and twist it into the braid from the<br>
> other side - cutting the cores shorter should have given you a bit of<br>
> overlap to work with. Solder the braid all around and then heat shrink the<br>
> works.<br>
><br>
> Sean<br>
> -------- Original Message --------<br>
> On Oct. 24, 2020, 22:09, David Colombo via Personal_Submersibles <<br>
> <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
><br>
><br>
> Rick, I am cutting the ots comms wire as well to shorten its lenght for<br>
> the yellow sub, and to get it thru the blue globe fittings. Attached are<br>
> photos of the shield which is a braided multi strand wire and the interior<br>
> wire which is also multi strand. I am assuming that when i rejoin the two<br>
> pieces there might be a small gap in which the sheilded braid may not<br>
> completely cover the inner core. Its kinda like a chinese finger braid<br>
> that tightens when pulled on the ends. Does anyone have any concerns about<br>
> the surrounding sheild braid not completely covering the inner core?<br>
> Since the cable is 50ft long, I have lots of lenght to play with.<br>
> David<br>
><br>
><br>
> On Sat, Oct 24, 2020, 5:51 PM Rick Patton via Personal_Submersibles <<br>
> <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
><br>
>> Yeah I have the surface head set system so should be fine. I had to cut<br>
>> the wire though to pass it threw the hull penitraitor so I hope it will be<br>
>> easy to re connect and not have any shielding leaks from any other stuff<br>
>> running.<br>
>><br>
>> On Sat, Oct 24, 2020 at 10:54 AM Sean T. Stevenson via<br>
>> Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
>><br>
>>> I think the boom mics on the surface headsets are pretty forgiving. The<br>
>>> issue with the diver mics is that they are of a noise canceling design. In<br>
>>> an effort to filter out regulator hiss and bubble noise, there are<br>
>>> diaphragms on both sides of the mic, and the transmitted signal is actually<br>
>>> the differential between the two, which is best when the mic is right in<br>
>>> front of the diver's mouth. A lot of divers find this position a bit<br>
>>> invasive and incorrectly push it away further into the mask cavity, so then<br>
>>> the mic is exposed to similar signals on both sides and becomes less<br>
>>> intelligible.<br>
>>><br>
>>> Not an issue for the surface hand mics or headsets.<br>
>>><br>
>>> Good idea with the transducer mounting. High and omnidirectional is<br>
>>> ideal, so you avoid the shadowing. Actually, this is one area where OTS has<br>
>>> a deficiency in comparison to one of its competitors, at least with the<br>
>>> diver units. The SSB-2010 needs to be mounted on a waist belt, or on a tank<br>
>>> cam band, and there's really no practical mounting position for that unit<br>
>>> that leaves the transducer in an optimal position. Even the low powered<br>
>>> Buddy Phone units that they sell for recreational divers are mounted on the<br>
>>> side of the head, and exhibit shadowing in the cross body direction. In<br>
>>> contrast, Divelink makes their diver worn units with transducers that sit<br>
>>> on top of the head, attached to the upper strap of the face mask. I'm still<br>
>>> inclined to buy OTS though. On a sub of course, you can mount your<br>
>>> transducer anywhere you like.<br>
>>><br>
>>> Sean<br>
>>><br>
>>><br>
>>> -------- Original Message --------<br>
>>> On Oct. 24, 2020, 14:33, Rick Patton via Personal_Submersibles <<br>
>>> <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
>>><br>
>>><br>
>>> Thanks Guys<br>
>>><br>
>>> In my case, the surface boat will not have the need to be underweight, I<br>
>>> will descend from the surface boat and it will just stay put except for<br>
>>> moving with the current. I won't have the thermoclines here in Hawaii that<br>
>>> most of you have but there are some of course. I will be using a headset<br>
>>> with boom mike so it will be almost touching my lips and I mounted the<br>
>>> transducer on the top of my hatch to minimize any ghosting on my end. I<br>
>>> agree Jon that it would be nice to have a topic on that. I would like to<br>
>>> put a face with all the guys here so where and when will be the next<br>
>>> convention? Oh yeah, the bloody coronavirus.Just got my trailer done enough<br>
>>> to get it weighed and a VIN number assigned to it so am stoked!<br>
>>> Rick<br>
>>><br>
>>> On Sat, Oct 24, 2020 at 9:26 AM Jon Wallace via Personal_Submersibles <<br>
>>> <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
>>><br>
>>>> My recollection from Lake Tahoe was that comms were good when surface<br>
>>>> boat was somewhere in the vicinity OVER the submarine. We didn't have to<br>
>>>> be directly overhead, just not too far away. When David piloted R-300 he<br>
>>>> ended up a good 600-800 feet away from us laterally when comms became<br>
>>>> difficult. Water column varied 60-100 feet (I think) in that area. Comms<br>
>>>> ended when our propeller cut the transducer cable (whoops), ALWAYS pull up<br>
>>>> the transducer when surface boat is underway, even at slow speeds. I'm<br>
>>>> just going to throw out a rule of thumb that has no emperical data to back<br>
>>>> it up, keep within the same distance laterally as the submarine is in<br>
>>>> depth. If the sub is 100 feet deep, stay within a 100 foot radius of it.<br>
>>>> If it's at 1000 feet depth, stay within 1000 foot radius of it. I think<br>
>>>> you could actually probably get away with a radius 4x depth and be ok, but<br>
>>>> keeping it 1-to-1 isn't a bad plan.<br>
>>>><br>
>>>> Sean is correct that water conditions matter as well as fresh vs salt.<br>
>>>> Even so, we should spend some time at our next "meet" to do some comm<br>
>>>> testing and publish the results on the web site just so we have some<br>
>>>> reference.<br>
>>>><br>
>>>> Notwithstanding the timber sound aesthetics Sean mentioned, comm<br>
>>>> quality between surface and R-300 was loud and clear when within the<br>
>>>> parameters I mentioned above. Cliff and David may have their own<br>
>>>> perceptions since they both manned the comms at some point during that<br>
>>>> weekend.<br>
>>>><br>
>>>> Jon<br>
>>>><br>
>>>><br>
>>>><br>
>>>> On Saturday, October 24, 2020, 03:01:32 PM EDT, Sean T. Stevenson via<br>
>>>> Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
>>>><br>
>>>><br>
>>>> Rick, ultrasound behaves quite a bit different than does radio as far<br>
>>>> as the attenuation relationship to distance. Things like shadowing, (where<br>
>>>> a diver's body / equipment or the hull or superstructure of your sub gets<br>
>>>> in between the direct line of sight between transducers) will have a much<br>
>>>> more profound affect on transmission effectiveness than distance alone.<br>
>>>> Similarly, thermoclines and haloclines can act as "surfaces" that refract<br>
>>>> or reflect the ultrasonic transmission, so it is important for the surface<br>
>>>> crew to lower their transducer into the same operating layer as the diver /<br>
>>>> sub. As a diver, I always report the presence and depth of any thermocline<br>
>>>> encountered on descent to the surface support for this reason. Also, the<br>
>>>> surface transducer needs to be suspended in the water column and not<br>
>>>> bottomed or lost in surface sea clutter, and the transducer needs to be<br>
>>>> weighted and boat speed limited so that it doesn't trail behind at an angle<br>
>>>> which is ineffective for transmission.<br>
>>>><br>
>>>> The rating in the published specifications for the OTS SSB-2010 (a 5<br>
>>>> Watt unit) is greater than 1000 meters in a calm sea, and ~200 meters in<br>
>>>> sea state 6 (Beaufort), but I presume that these are ideal scenarios<br>
>>>> whereby the surface and dived transducers are suspended at the same depth,<br>
>>>> in the same (vertical) orientation, with clear line of sight and no<br>
>>>> interfering reflections, and also with no squelch applied. Real-world<br>
>>>> conditions are obviously somewhat different, and the environment can<br>
>>>> actually be somewhat noisy at typical channel frequencies, requiring the<br>
>>>> application of some squelch and the consequent loss of range.<br>
>>>><br>
>>>> Rated frequency response is ~300 Hz to ~3000 Hz, which covers most of<br>
>>>> the vocal range, but will not reproduce true timbre of voice. It is fine<br>
>>>> for intelligible speech, but not for e.g. music.<br>
>>>><br>
>>>> I have used this unit as a diver only, so my impression may be also due<br>
>>>> to the influence of the earphone / microphone assembly in my mask. Choice<br>
>>>> of mask makes a difference (shape and size of gas cavity), as does<br>
>>>> proximity to the mic. You need to be almost kissing those OTS diver mics to<br>
>>>> get decent sound. That said, my experience with the SSB-2010 was decent,<br>
>>>> but that was in the context of a dive team separated by a few meters at<br>
>>>> most, and at relatively shallow depths (limited distance from surface unit)<br>
>>>> where helium based breathing gas was not required.<br>
>>>><br>
>>>> I can't speak to long range effectiveness, other than at Flathead last<br>
>>>> year I was surface support for Cliff in the R-300. He was using a SSB-2010,<br>
>>>> but the surface unit we had was something different - one of the surface<br>
>>>> specific boxes, and I don't recall the model (Cliff?). There were times at<br>
>>>> which we lost him and had to reposition the boat to reacquire him, and<br>
>>>> others where we could hear him but he couldn't hear us, but I can't speak<br>
>>>> to the exact ranges, depths or boat speeds that caused those issues. It was<br>
>>>> never such a sustained loss of comms that the dive had to be called. Likely<br>
>>>> the result of relative orientation or depth, or shadowing of the<br>
>>>> transducers.<br>
>>>><br>
>>>> Sean<br>
>>>><br>
>>>><br>
>>>><br>
>>>> -------- Original Message --------<br>
>>>> On Oct. 24, 2020, 12:10, Rick Patton via Personal_Submersibles <<br>
>>>> <a href="mailto:personal_submersibles@psubs.org" target="_blank">personal_submersibles@psubs.org</a>> wrote:<br>
>>>><br>
>>>><br>
>>>> wanted to hear from those who have and have used the OTS comms system.<br>
>>>> I was wondering how you liked the system and what your max clear<br>
>>>> audible range was.<br>
>>>> Thanks<br>
>>>> Rick<br>
>>>><br>
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