[PSUBS-MAILIST] 1. Re: OTS and motor controller noise

Thu May 1 19:08:55 EDT 2025

Hi all,  For that very reason I have made a housing attached to the motor
with the controller and canbus interface all within.  I used a Kelly
controller and the housing for all the components is about 100 mm diameter
and about 50mm deep.  So I have my 72 volt power cord and a CANbus cable
into the housing.  Hopefully no noise with my OTS.  All 11 motors configured
in the same way.  Hugh

-----Original Message-----Si about 100 mm diameter and about 50mm deep
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Sent: Wednesday, 30 April 2025 1:40 PM
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Subject: Personal_Submersibles Digest, Vol 136, Issue 33

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Today's Topics:

   1. Re: OTS and motor controller noise
      (Jon Wallace via Personal_Submersibles)

----------------------------------------------------------------------

Message: 1
Date: Wed, 30 Apr 2025 01:39:18 +0000 (UTC)
From: Jon Wallace via Personal_Submersibles
	<personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion
	<personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] OTS and motor controller noise
Message-ID: <90593753.3387481.1745977158206 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

 Lol, just saw your comment about the Theremin.? So maybe we can give a
rendition of the 1812 Overture from 100 feet??? ?:)? :) Jon

    On Tuesday, April 29, 2025 at 08:31:52 PM EDT, Alec Smyth via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Just finished another round of experimentation. This is fun.
1) Changing channels did absolutely nothing at all. All four were
equally?noisy.2) Turning on squelch was the opposite, it was so effective it
completely eliminated the noise. There was not even minimal white noise and
I wondered if the comms box was still on. However, I do not expect it to
work that well in the water. I know I've tried it on dives and it was?an
improvement, but not to this extent. My guess is that it's because with the
props spinning in air, thruster currents are drastically lower.3) Shielding
with aluminum foil was super interesting. I could hear the attenuation go up
and down just as I held a sheet of foil in my hand and moved it in and out
of the space between one of the controllers and the comms box. D'you guys
know what a Theremin is? Wrapping the OTS box in foil certainly did help
attenuate the noise, but isn't a complete solution because of small gaps
remaining, for instance for the cables. I'd say the noise reduction was
probably 50-75%.
Conclusion... I'll plan to both relocate the OTS box to the quietest area,
and use squelch. Maybe get fancy by making an aluminum pocket into which
I'll slide the SSB-2010, as a method of mounting it to the hull.?
Alec

On Tue, Apr 29, 2025 at 4:46?PM Jon Wallace via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

 Alec, can you also test channel 3.? I'm literally getting no interference
on Channel 3 which is 31.25khz upper side band.? Using this channel would be
a good work around until an electronic fix can be achieved that protects all
channels.
Jon

    On Tuesday, April 29, 2025 at 01:01:03 PM EDT, Alec Smyth via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 I happen to have my former sub Snoopy back in the shop because her current
owner has engaged me to recommission her. The job is about 99% done, and the
comms already installed, so I just conducted an experiment. I have the same
setup as Dave; SSB-2010 inside the cabin running on its own dry cell
batteries, connected to the transducer by a cable that is potted through a
penetrator without cutting. I had left that cable longer than needed, in
case the owner decided he wanted the OTS unit somewhere different.?
I turned on the thrusters and started moving the OTS all around inside, and
also routing the cable along different paths. Here are the conclusions:
1) As one would expect, there is much less noise when the thrusters are at
either zero throttle or full throttle. All the noise is in between, when the
signal is choppy.2) The noise is completely insensitive to the position of
the cable. BTW the cable I'm using?was the OEM cable on another comms system
similar to OTS. It's a small diameter shielded single conductor, where the
shield is not grounded but used as a second conductor.3) Almost all of the
variation in noise comes from proximity of the OTS unit to the speed
controllers. There is also a bit of noise if its placed close to the battery
cables, but it's nothing compared to the noise emanating from the
controllers.
So... the conclusion, at least in my case, is to place the OTS unit as far
from the speed controllers and battery cables as possible. David, does that
match the location of your OTS unit?
Best,Alec
On Tue, Apr 29, 2025 at 12:54?AM David Colombo via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

Jon, youve got me thinking on this one. In the VAST, i have the diver unit
inside the sub, a continuous non cut cable potted to the thru hull
penetrator. The diver unit has its own 6 AA battery pack. With the pair of
36v 101's, and wearing the headset, i have not had any issues with bleed
over noise. I am planning on adding the topside unit inside as a new comms
like you. My 101's are controlled by their own minnkota pwm which are on the
36v lipo4 battery pack.? The hotel loads are on their own 12v lipo4 battery
pack, which is where i plan on connecting the topside unit.? I will run a
test to see if i can find any signal interferance using the hotel load
battery vs its own 2-6v battery pack, and let you know what i find.

On Mon, Apr 28, 2025, 4:24?PM Alec Smyth via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

I've had mine to 250', but it was inside the sub. That said, the effect on
the audio quality was remarkable. It was perfectly clear, but if you ever
talked to your friends through a long garden hose as a kid, that was exactly
how it sounded. Which was great, because it made it feel spooky and deep!
On Mon, Apr 28, 2025 at 4:35?PM Sean T. Stevenson via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

I have had a SSB-2010 a bit deeper than 130 as a diver without flooding the
housing, but I don't know how deep it will go without compensation.? That
limit is the standard recreational diving depth limit for
no-mandatory-decompression-stop diving, and it is likely that it was both
designed and rated accordingly.?? These units have no helium speech
descramblers, so they are of limited utility for ambient pressure divers as
you go deeper. The donald duck voice on top of the limited bandwidth of
ultrasonic comms at all makes intelligibility a challenge.

I had the unit to ~165 fsw, and I suspect that you could push it deeper, but
you would void any warranty.? I'm using PowerCom 3000D units now, and these
have similar depth ratings.

Sean

-------- Original Message --------
On 2025-04-28 10:59, Jon Wallace via Personal_Submersibles  wrote:

 SB-2010 is rated to 130 feet by OTS.? Has anyone tested one to deeper
depths?

    On Monday, April 28, 2025 at 01:15:01 PM EDT, hank pronk via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Jon, put the whole unit outside the hull.? I have zero issues with this.? I
just put fresh batteries in for each diveHank Sent from my iPhone

On Apr 28, 2025, at 10:16?AM, Jon Wallace via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:

? Not a lot of room to work with of course inside the cabin.? My controllers
are mounted up near the top of the hull, the coax comes in from the bottom
and is probably only about 18 inches laterally from the controllers.? The
coax cable thru-hull is only 5/8 inch diameter (15.8 mm) so PL259's won't
fit through it to allow me removal for maintenance which is why I opted for
SMA.? I suppose I could try it since I won't be removing the cable regularly
but it's definitely going to be a PIA change.
No I'm not sure whether the noise is electrical or acoustic in source but
now that you've asked I can tell you that the controllers make an audible
tone when the PWM is active, even with the OTS off.? The tone changes of
course depending upon the PWM frequency I select, but it is always there.?
The same tone comes out the OTS, but amplified.
Jon

    On Monday, April 28, 2025 at 11:51:58 AM EDT, Sean T. Stevenson via
Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

Two things I would look at:

1) Relative location and shielding between the motor controller and the
transducer cable.? Is additional shielding (conduit?) possible?

2) I have encountered problems in the past with noise on coax due to
impedance mismatch / partial signal reflection at any connectors. In my
experience, this is solved by moving from RG58 up to RG8, but you don't have
that option because the transducer is a potted assembly. If you have enough
cable tail available to experiment, I wonder about swapping the SMA
connectors for PL259 to see if that makes a difference.

Are you certain that the noise you are hearing is being introduced
electrically, and not acoustically in the ultrasonic range of the
transducer?

Sean

-------- Original Message --------
On 2025-04-28 06:47, Jon Wallace via Personal_Submersibles wrote:

Hey folks,
My OTS STX-101 receiver is picking up some fairly significant and annoying
electronic noise from my Roboteq PWM motor controllers.? I tried changing
channels on the OTS hoping a different frequency might help but it didn't.?
I also tried changing the controller PWM frequency between a range of 10khz
and 24khz but nothing between those frequencies made a significant
improvement.? The noise is enough to override the normal squelch setting but
at the same time a strong communication signal through the OTS transducer is
enough to override the noise.
My configuration has the transducer outside the hull and receiver inside the
hull which required cutting the cable.? I potted the cable in a thru-hull
and reconnected the cable inside the cabin with RG-58 SMA connectors
(soldered, not crimped).
In talking with a couple other folks it seems I am not alone in this
experience.? Some others have found that using local batteries instead of
tying into the same batteries used by the motors has significantly reduced
the noise, however in my case I am already using a separate battery isolated
from the motor batteries.? Another choice that has seemed to make a
difference is mounting an SB-1001 outside the hull and running the headset
wires through the hull instead.
Anyone else have similar experiences with OTS?
Jon
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