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Old 03-03-2021, 17:31   #1
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Starlink 'beta' passive gimbal experiment?

-before you post, yes, I know that starlink is limited to only one address at a time right now

So I just received the email that I may pre-order starlink for my marina address. I am a liveaboard so even if it's used at a 'fixed address' for the time being, it is still worth it for better service for me currently, as a hold-over until the potential release of a truly mobile-capable device, which may be years away. Even with a device that allows roaming, the first iterations may be designed for road/rv use, and not be able to adjust to a rocking boat. All just speculation, of course.

Anyway, being highly interested in this technology, I was considering trying to develop a passive gimbal system to allow dockside use of starlink at my unprotected, high traffic marina, which I think would be great for experimental purposes. (lots of rocking and rolling to see how well the design may or may not work)

In excitement for this, I've drafted a very basic, minimal design, which could be made out of off the shelf parts. I'm interested to hear feedback about what might be improved, or perhaps some solid reasons why the idea of a passive gimbal may be just completely unusable for starlink? It's the first time I've tried anything like this so I'm guessing there's a number of variables I'm not considering.

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

Design v1:

Intended to be mounted to stern railing / deck

I've not specifically modeled the fittings here, but they can all be found on mcmaster-carr:

bearing: https://www.mcmaster.com/bearings/mounted-bearings/

u-clamp to mount bearing: https://www.mcmaster.com/u-bolts

fixed and adjustable-angle fittings: https://www.mcmaster.com/aluminum-sl...aming-fittings

The green blocks are clamp-on weights, which are also readily available, for example from exercise equipment shops.

openSCAD code to make this: https://pastebin.pl/view/58d04ab7


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Old 03-03-2021, 19:12   #2
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Re: Starlink 'beta' passive gimbal experiment?

My concern would be how sensitive the gimbal would be. Minor movement of the boat may not be enough to "activate" the gimbal. I would think that if the boat is moving then it might be enough to keep the antenna pointed in the correct direction.

Now I have read that the antenna needs to be "pointed" to the north. The word "pointed" is what the document said. Now why does it need to point anywhere? These are not satellite dishes that need to be set for a geosync satellite. So why point it to the north?

Not sure what is going on with Starlink. Good luck.
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Old 03-03-2021, 20:02   #3
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Re: Starlink 'beta' passive gimbal experiment?

Try it first without a gimbal. There's a good chance it will work fine.

As you probably know the Starlink antenna is a phased array antenna that can track satellites without moving the antenna - I believe over 100 degrees of arc. The satellites are constantly moving across the sky at a pretty good clip. The antenna uses a small motor to point the phased array antenna in generally the right direction when you first setup it up and then the phased array antenna just sits there picking up anything passing through that pretty big piece of sky. The phased array operates at the speed of light. Any rolling you might get from a wake shouldn't bother it.

Of course, they may have put something in the beta consumer software that assumes the antenna is fixed to a solid structure - but in that case your gimbal might confuse it too.

Musk's SpaceX missile recovery ships are using Starlink at sea.

I've already got a place picked out on my boat for my Starlink antenna but I'm waiting for them to upgrade the software to let me move between different cells.
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Old 03-03-2021, 21:46   #4
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Re: Starlink 'beta' passive gimbal experiment?

@CarlF

I can't find it right now, but I read a post recently on reddit of a user in an unprotected marina, who said they have success with the starlink mounted without a gimbal in calm conditions, but moderately windy usage causes it stop functioning for a time. So I believe I already have my answer there for trying with no gimbal.
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Old 03-03-2021, 23:40   #5
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Re: Starlink 'beta' passive gimbal experiment?

I have Starlink with the stock antenna on my boat, 83'. No gimbals. Antenna is in a big open space on my foc'sle. I liveaboard at a private dock open to ship and boat traffic wakes. I'm at about 46įN and the dish is nearly flat with a slight north lean. The dish needs an open sky and in my experience needs to be 10 or more feet from a cabin or mast. I don't know how it would handle sailboat rigging.
Big wakes can cause a loss of service until it reacquires the signal. Anywhere from seconds to minutes. Small wakes usually don't disrupt service. In calm water I can maintain service while cruising within my cell. No idea what cell size is or where borders are. I've gone 10 miles w/o hitting a border. The antenna takes a few minutes to recover from a course change.
Starlink has been much better than my former wireless internet. Wireless was 2-3mbps and Starlink seems to be 15-18mbps, but does have some slow times, and that could be on a choppy day. Usually I have no trouble streaming tv and downloading large files over gb. Maybe as Starlink adds subscribers speed will change.
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Old 04-03-2021, 00:35   #6
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Re: Starlink 'beta' passive gimbal experiment?

I have seen one on the deck of a boat in a slip. the antenna was moving around a bit when the boat rocked big and did not move with little rocking. I don't know if signal was in and out durring it's move or if it stayed.

it draws ~100w so it's a pretty big hog if you are not pluged in.
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Old 04-03-2021, 02:09   #7
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Re: Starlink 'beta' passive gimbal experiment?

Interesting. Keep us posted on the progress/success.
I like the idea of being able to adjust the gimbal sensitivity with the sliding weights.
Quote:
Originally Posted by sona1111 View Post
-before you post, yes, I know that starlink is limited to only one address at a time right now

So I just received the email that I may pre-order starlink for my marina address. I am a liveaboard so even if it's used at a 'fixed address' for the time being, it is still worth it for better service for me currently, as a hold-over until the potential release of a truly mobile-capable device, which may be years away. Even with a device that allows roaming, the first iterations may be designed for road/rv use, and not be able to adjust to a rocking boat. All just speculation, of course.

Anyway, being highly interested in this technology, I was considering trying to develop a passive gimbal system to allow dockside use of starlink at my unprotected, high traffic marina, which I think would be great for experimental purposes. (lots of rocking and rolling to see how well the design may or may not work)

In excitement for this, I've drafted a very basic, minimal design, which could be made out of off the shelf parts. I'm interested to hear feedback about what might be improved, or perhaps some solid reasons why the idea of a passive gimbal may be just completely unusable for starlink? It's the first time I've tried anything like this so I'm guessing there's a number of variables I'm not considering.

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

Design v1:

Intended to be mounted to stern railing / deck

I've not specifically modeled the fittings here, but they can all be found on mcmaster-carr:

bearing: https://www.mcmaster.com/bearings/mounted-bearings/

u-clamp to mount bearing: https://www.mcmaster.com/u-bolts

fixed and adjustable-angle fittings: https://www.mcmaster.com/aluminum-sl...aming-fittings

The green blocks are clamp-on weights, which are also readily available, for example from exercise equipment shops.

openSCAD code to make this: https://pastebin.pl/view/58d04ab7


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Old 04-03-2021, 10:41   #8
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Re: Starlink 'beta' passive gimbal experiment?

The reason they want it pointed slightly to the north is because the satelites are not in a polar orbit so they overlap and are more concentrated in the northern latitudes . I believe they only have 9 sats in polar orbit. As the numbers grow direction will become less of an issue. The flat dish is about a thousand more or less little phased array antenna's printed on a circuit board. Right now they work better in Canada and the UK then in the US but that will change in time. I'm sure they will program them to only be Geo-Locked out of non co-operating countries that banned sat phones like India , and China north Korea Cuba Iran and who knows how many more. I'm only interested in the open ocean and friendly shores ! Soon we could have superior AIS over hundreds of miles instead of VHF line of sight to the horizon. New kinds of Eperbs. The future looks bright. These are just my own ramblings. Don't quote me on anything I've said. I could be wrong about everything.
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Old 04-03-2021, 10:45   #9
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Re: Starlink 'beta' passive gimbal experiment?

We know KVH and others make gimbaled dishes for satellite reception for boats. Canít imagine it will be too long until an enterprising company we beginning manufacture and sale of something for Starlink.
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Old 04-03-2021, 11:27   #10
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Re: Starlink 'beta' passive gimbal experiment?

Quote:
Originally Posted by garychurch View Post
We know KVH and others make gimbaled dishes for satellite reception for boats. Canít imagine it will be too long until an enterprising company we beginning manufacture and sale of something for Starlink.
The KVH systems (I worked on the firmware of the first generation of the KVH antennas) are for a very different purpose - keeping an antenna actively aimed at a single, relatively static, point in the sky with a high degree of accuracy, even as the platform it's mounted on yaws, pitches, and rolls. Starlink antennas are different, as someone else already pointed out, in that they use phased array technology to steer the antenna. Electronic steering of the antenna, without any physical movement, is super fast, with slew times measures in milliseconds, as compared to multiple second on mechanically steered units. This allows the Starlink antenna to track fast moving satellites in low earth orbit. If they use any kind of feedback or phase locking, they should be able to hold a lock on the satellite even if the platform underneath moves. But, if they are assuming a stationary platform, and just use the orbital parameters of the satellites to know where to point the beam, then movement could significantly affect the system.

I suspect (just my opinion) that Starlink probably implemented the latter in their initial design, as it is simpler. All you need is your current position and a database of the satellites and their orbits, and you're good to go. Adding motion detection and/or a feedback loop to maintain a lock on the satellite should not a huge leap, provided the hardware can support it. The fact that SpaceX have already announced imminent significant improvements in latency and speed, just with software upgrades, implies that the hardware is capable of better tracking.

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Old 04-03-2021, 11:37   #11
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Re: Starlink 'beta' passive gimbal experiment?

Don't waste your time.
Our Starlink works fine on our boat in the marina. We are in a relatively protected marina but, when the winds whip through at 50 knots, the boat rocks pretty well. The dish focuses electronically once it is pointed in the right direction. Musk says it focuses so fast that it will work on a moving RV.
Our download speed has been getting progressively faster and now seems to vary between 60 and 150. I did see 420 once but I don't check it that often. There are still a few interruptions but only noticeable on a zoom call. Typically 3-5 seconds.
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Old 04-03-2021, 11:49   #12
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Re: Starlink 'beta' passive gimbal experiment?

Thanks for this. Nice design. I recently received my Starlink equipment and will be setting it up on my boat soon, so it is great to see this. I also wonder if the gimbal system is necessary or not; Iíll try using it without and post an update once I do.
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Old 04-03-2021, 12:00   #13
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Re: Starlink 'beta' passive gimbal experiment?

As with regards on using on boats. I do know that they tested it already on moving airplanes.
They have currently restrictions on their license to sell units which can be used on vehicles.
Further, they land the SpaceX rockets on the rolling and pitching drone ships, would be highly surprised if the do not use their own satellite system for the data transfer regarding this.

Anyone who would like to see what's inside the dish:

https://youtu.be/QudtSo5tpLk
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Old 04-03-2021, 13:18   #14
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Re: Starlink 'beta' passive gimbal experiment?

The starlink antenna is not a reflector, but a phased array and does not need to be pointed precisely at anything. A website examining the issue said the phased array should be able to keep transceiving even with some 'ocean motion'.

The antenna has a built in pan and tilt motor to point it in the correct direction. (I think this is what is behind the ONE ADDRESS limit. My guess is they program the angles for your specified GPS coordinates into the controller so it knows which way to point itself when turned on.)

IIRC the antenna is a bit large (30" +/- maybe?) and will likely be affected by wind as well as wave. Not sure if your gimble will help that, and may make it more susceptible to wind induced movement.
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Old 04-03-2021, 14:46   #15
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Re: Starlink 'beta' passive gimbal experiment?

Quote:
Originally Posted by OS2Dude View Post
The starlink antenna is not a reflector, but a phased array and does not need to be pointed precisely at anything. A website examining the issue said the phased array should be able to keep transceiving even with some 'ocean motion'.

The antenna has a built in pan and tilt motor to point it in the correct direction. (I think this is what is behind the ONE ADDRESS limit. My guess is they program the angles for your specified GPS coordinates into the controller so it knows which way to point itself when turned on.)

IIRC the antenna is a bit large (30" +/- maybe?) and will likely be affected by wind as well as wave. Not sure if your gimble will help that, and may make it more susceptible to wind induced movement.

There is an app, there is always an app, that uses the phones built in GPS to get the lat, long, and sends that info to the dish controller/wi-fi hotspot, this tells the dish the appropriate declination to set, to start looking for satellites. After you line the dish pivot axis ~East/West.
I can get one, but my local ISP hasn't gotten my that aggravated, to switch, yet.

Best wishes
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