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Starlink

I still cannot understand why Iridium have such a rubbish data rate – 2400 bits/sec

As far as I know the link between the satellites is the bottleneck. It is apparently 10 Mbit only. Each connection with 2,4 kbit plus some correction etc. maybe consumes 3,6 kbit raw bandwidth. So the network can support abut 2700 simultaneous calls in one satellite ring. As far as I remember they have 6 rings. Now if you increase the bandwidth for each connection those 10 Mbit will be congested by just a few connections.

The Iridium network was designed for voice communications and maximum global availability. High speed Internet was no design goal. They currently work on a new satellite constellation which will sometime in the distant future support more bandwidth but I think not at the price point to deliver affordable Internet to rural Africa.

www.ing-golze.de
EDAZ

Hey all,

News flashed by today that Starlink launched another 90 satellites, now having more than a 1000 satellites flying (falling?) around planet earth. Beta testing is underway in the US and launch for Europe is scheduled for 2021 (iirc).

Can this be an option to provide us with in-flight weather/data services in Europe? I assume that small receivers will reach the market soon enough and since it is brand new tech, I also assume the cost will be lower per MB than say Iridium, that Golze is successfully using for their solution. Or are the use case for Starlink completely different and thus require more permant like installations of the receivers?

Just some thoughts on a Sunday evening :)

ps. Can’t seem to alter the subject after posting it, it should say ADS-B provided weather(!) ds. [ done, I think – Peter ]

Cheers,
Martin

Last Edited by martin-esmi at 14 Mar 19:49

Boy, wouldn’t that be nice since Im getting ADSB as soon as Germany opens up. Installation is scheduled for May.

KHTO, LHTL

Pricing seems to be about $99 per month, plus an upfront cost of around $400 from what I’ve heard.

But the issue seems to be the size of the receiver. Too large for GA. Ok for an airliner, but not suitable for an SEP.

EIWT Weston, Ireland

The biggest problem seems to be the antenna. I don’t have a license free picture but look it up on Google. It is the size of a pizza and moves to track the satellites. I see no way to mount anything like that on a small plane. From experience I can tell a key requirement for a successful solution is a tiny more or less omni directional antenna. Any solution with big antennas which have to be aimed is bound to fail commercially.

www.ing-golze.de
EDAZ

A movable pizza won’t be suitable either for airliners… only awacs.

LFMD, France

greg_mp wrote:

A movable pizza won’t be suitable either for airliners… only awacs.

Maybe they could “flatten” it a bit like the current antennas:

But any moving antenna is not suitable for general aviation. We rather need lower bandwidth with a very simple antenna. Obviously the Starlink satellites could for example broadcast 978 MHz UAT signal from the satellites and cover every part of the globe. But there is no business case for such ideas. The only way to go is to use some system which is already up in the sky for other purposes.

www.ing-golze.de
EDAZ

They need to talk to uavionix. They’re head and shoulders above everyone else when it comes to miniaturization for GA, as far as I’ve seen.

LSZK, Switzerland

Sebastian_G wrote:

and moves to track the satellites

Negative.

It uses digital beamforming to track the satellites. The moving part is only initial, to align itself with the most optimal path since Elon does not trust humans. However, beamforming is still fully possible without the initial moving part since airplanes fly mostly straight and level.

A smaller antenna array using larger codes that would fit on top of a small GA plane could still perform adequately for smaller data rates. Weather data doesn’t require a 100 Mbit/s data link.

Last Edited by Dimme at 14 Mar 23:47
ESME, ESMS

Looking at their website it is clearly intended for a decent size dish if you want broadband speeds.

One cannot get the required signal to noise ratio with a small antenna. It’s just physics. That’s why satellite phones never got small, and why mobile phones never used satellites but instead cover the earth with a huge quantity of expensive towers and microwave links. The NSA can pick up mobile calls with a satellite but theirs has a huge antenna on it, and they don’t need to transmit to your phone

One can trade data rate for S/N (Shannon etc) but only if the transmitter is offering a slow speed option. I can’t see this mentioned; is there some info on it?

$99/month is quite expensive. Golze ADL is about €25/month. The old Avidyne MLX770 and Garmin GSR56 cost best part of $100/month (very few people were happy to talk about how much they pay) but few have been sold and Avidyne abandoned theirs a few years ago. This old writeup covers some of this, and ends with my abortive experiments with Thuraya and eventually with moving to the Golze ADL.

And Golze could use whatever network they can; it doesn’t have to be Iridium. It is just that Iridium is the only option right now that actually works and is usable in the right price band.

The electronics itself is not a challenge; everybody has access to the same technology. How much you cram into the box is just according to how you integrate the design, how small surface mount components you choose to use, etc.

Previous Starlink thread merged with this one, and there are some interesting older posts there.

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Shoreham EGKA, United Kingdom
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