Why ?

What does it matter where the dish is ? There is a dish, with a paid subscription. You should be able to lob it on the roof of the car and drive around with it. The cubestats are moving at thousands of miles an hour anyway, a few more dozen shouldn't have any kind of impact.

Although there are technical limitations related to the number of subscribers each ground station can support my guess is that the principle concern is scalpers.

I hope that when laser links can connect you to any ground station, there are plenty of satellites to provide bandwidth and there is no waiting list for terminals then the restrictions will disappear. There is a possibility that competition with Kuiper will end Starlink restrictions - in 2050 - if Jeff can manufacture engines.

Scalper in this case is probably Musk.

So pay an extra $25 a month, or leave your dish at home. No putting it on your yacht, truck, job or campsite. At least not without paying for a 'premium' roaming service.

Or there may be some regulatory restrictions, ie operator license is only for fixed endpoints. Which is probably true for some countries, but Inmarsat managed portability with BGAN kit, widely used by reporters.

Starlink was clearly advertised for use in fixed locations only. There were regulatory restrictions as well as technical, both of which have been relaxed over time.

Inmarsat is a contraction international marine satellite. They started by obtaining licenses for mobile use because most ships do not remain at fixed locations. Back when I worked with their kit ('80s), the satellites were referred to as Atlantic, Pacific and Indian (as in ocean). They have expanded since then, but their main target as always been mobile, with the size of that mobile reducing over time. The kit I worked on would have capsized some of the boats customers hoped could get a satellite phone/fax.

Yup. As a young telecomms sprog, I remember getting excited at the prospect of an STM-1 satellite connection. Would have needed roof loading capable of supporting a 15m dish, and cost a fair chunk of a geostationary satellite.

But as sales would say, it'd be technicaly feasible.

Even though I'm an excellent shot, I do miss sales sometimes. I did get to have some fun looking at naval applications, like the cunning mounts hiding under domes. Including whether those could be installed on swaying skyscrapers. Also been puzzled about cultural differences, ie VSAT solutions for DR were far more common in the US than Europe. Conclusion was the US is more used to things like hurricanes & tornados, so pulling a spare dish out of stores restores service faster than waiting for cable restoration.

You aren't comparing like with like. Inmarsat uses satellites in geostationary orbit 22,000 miles away. There is only a dozen of these satellites spread around the earth so they are expensive what with high contention and limited bandwidth. Starlink satellites are in low earth orbit constantly moving over the sky. That means that regardless of where you are on earth (barring the poles), you're going to have a multitude of satellites overhead. You could be in the middle of the ocean, a desert, a city, anything with a clear line of sight and there will be one overhead.

Now it may be that the 1st generation of Starlink terminal (dish and box) isn't so great if you mount it to a boat because it is not gimballed & motorised. But if you're stationary in a marina, a campsite, or a cabin in the woods then there is absolutely no reason the existing dish shouldn't function exactly as it does at home - lock onto a passing satellite, handshake, authenticate, internet happens. Any additional charge imposed for "roaming" is nothing to do with any technical issue, it's merely a cashgrab.

Because you're moving into an area with OTHER folks with a paid subscription, and they shouldn't suffer because you're trying to snaffle their bandwidth.

It's not first-come, first-served. You get what's left over. ""Starlink prioritizes network resources for users at their registered service address."

Also, there may simply not be satellites in view. Granted, with the metric assload of satellites they're putting up that's probably not an issue, but they need to put in in the fine print anyway.

People moving around with their satellite dish are most likely moving to places with less contention, not more. e.g. someone driving out of a city to go on a camping trip. I very much doubt it makes any difference to contention in those sparsely used areas.

And if there were some potential for abuse then I'm quite certain that Starlink could stop it with a reasonable usage policy, e.g. roamers only get 30 days in a year or more aggressive bandwidth throttling.

They are not cubestats, and they are not built to support mobile. You'll have to wait a couple of years for AST to get their sats up, and then sell a kidney before they will let you connect to them with your 5G phone.

If you take enough Starlink dishes to the same location, they will run out of bandwidth. E.g. if you have a few thousand people turn up for a festival, and they are all camping in a field with their dishes, then there's no way Starlink can provide enough bandwidth. In that case, they quite reasonably prioritize the fixed dishes rather than the roaming ones. E.g. that means that the people in the village near the campsite can continue to work from home using their Starlink connections.

Regarding moving: One of the problems is Doppler shift. If a radio transmitter and a radio receiver are moving towards each other, then the receiver will see a higher frequency than the transmitter is actually transmitting. Similarly a lower frequency if they are moving away. This means that a moving dish will see different satellite frequencies than it expects, and will probably fail to decode them. This happens even at typical car speeds.

It is possible to correct for Doppler. And they must be doing that to account for the satellite movement. However, they likely design their correction system with the expectation that the ground stations were not moving.

Another problem is that I believe that the ground stations shape the transmissions to go to the satellite. If they are aiming off to one side, and you drive around a bend, suddenly they are not pointing at the satellite any more. It is possible to fix this, with the right sensors on the base stations. But since Starlink are selling a fixed service, there is no reason for them to incur the cost of those sensors.

Regarding doppler shift in a car:

Speed of light = 1 billion Km/hour

Speed of Car = 100 Km/hour

Speed of Car as fraction of Speed of Light = 0.0000001

Not saying you are wrong, but the channels to Starlink must be pretty narrow for doppler shift to be a problem.

Yes but if the baud rate is high enough, a small shift like that could alter the timing of symbol reception at either end

It's not a technical limitation. Remember that they've recently signed up a couple of airlines to provide in-flight internet service. Airplanes travel quicker than cars!

It'll just be down to bandwidth allocation, and the chance to extract more money is a side benefit.

So the doppler shift of the car doing 100kn/h is a problem? But the doppler shift of the satellite doing several thousand km/h is not?

One is a small problem, that was not designed for, and is uncorrected.

The other is a big problem, that was accounted for in design, and is corrected for.

That's the difference. Whether the first problem is so small that it shouldn't actually be a problem, I have no idea.

If Starlink can't cope with a thousand people camping in a field then how would it cope with many tens of thousands in a mid size city? This isn't an excuse.

As for doppler shift, this is already a thing. The satellites are constantly moving towards or away from you. It might be a technical limitation of the 1st gen terminal that it's not designed for trucks / boats but that has nothing to do with roaming per se.

We know that movement is NOT an issue... As the same starlink sats are capable of keeping comms at full speed with jets. They tested it with military aircraft and have just signed a deal with Hawaiian air ( https://www.itpro.co.uk/network-internet/wifi-hotspots/367475/spacex-starlink-signs-first-in-flight-wi-fi-deal ).

It is more of an issue with regulatory approval for 'mobile' stations. I am waiting for starlink on a boat. The 'maritime' permissions are currently for (if I recall correctly) under 10 mobile maritime stations (as a test). The movement is a regulatory not a technical issue.

"We've reached out to SpaceX"

Are you trying to say that you ASKED SpaceX?

They socialised the question?

I'll need to update our bullshit bingo cards for our next all-hands meeting...

We would have invited SpaceX for a quick scuba in our think-tank, but were scared Elon would call us a "Pedo"

When Starlink launched Musk was saying that they were going to follow a single price model regardless of static / moving dishes. Presumably they've decided they can just screw people for some extra $$$ by discarding that idea.