[PSUBS-MAILIST] OTS

Sat Oct 24 16:33:21 EDT 2020

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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