[PSUBS-MAILIST] OTS

Sat Oct 24 20:50:52 EDT 2020

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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