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No. Your aim has to be much better than the human musculoskeletal system is capable of. Go outside on a dark night and point a laser pointer at a building 100 m

No. Your aim has to be much better than the human musculoskeletal system is capable of. Go outside on a dark night and point a laser pointer at a building 100 meters away. Hold it as steady as you can. Have a friend take a closeup video of the bright spot from 2 meters away. Notice how much the dot wobbles around. Now imagine doing the same experiment where the dot is 540km away -- 5000 times farther. That's the altitude of a Starlink satellite. You might get lucky and sweep across the satellite once in a while but most of the time the beam will be many kilometers away from it. It's not quite this bad; the beam will be fairly wide at 540km which makes the problem a little bit easier, but it's still basically impossible to hold the beam on the satellite for more than a few milliseconds. And even that wouldn't work because you can't collect a strong enough signal from a satellite with an antenna the size of a cell phone. You need a parabolic dish or phased array about the size of a pizza box (minimum) to boost the gain enough. Satellites don't transmit with a lot of power, so your antenna needs a large area. Good news: You don't have to do it this way. If you limit yourself to short text messages you don't have to aim the beam or use a lot of gain. That's how Iridium works. But if you need a fatter pipe: Carry an antenna the size of a pizza box with you. Set it on the ground, let it acquire the satellite, then talk to it with your phone over wifi or bluetooth. Because this antenna uses closed loop feedback it can point very accurately at the satellite and stay locked on. This is basically how the Starlink antenna works, except Starlink would prefer that you not move the antenna from place to place (yet). And you'll need a big battery to power the antenna. It needs about 100 watts for transmitting; probably quite a bit less for receiving.

lxgr 5y ago
Antenna gain is not binary: There's things in between laser pointers and lightbulbs. > Your aim has to be much better than the human musculoskeletal system is capable of. > You need a parabolic dish or phased array about the size of a pizza box (minimum) to boost the gain enough. No – there even is a very specific counterexample: https://satpaq.com/ https://satpaq.com/ I doubt that Apple would use that approach, though. If anything, I'd imagine that they'd use existing (for 802.11 and LTE) beamforming capabilities.
- dreamcompiler 5y ago
  Satpaq is yet another short message service. It seems to use a semi-directional antenna. It doesn't require exact pointing because the bandwidth is very low. You cannot surf the web with it and you certainly cannot upload Youtube videos with it. The only reason some pointing is required for Satpaq is that it uses GEO satellites which are a lot farther away than LEO, so concentrating most of the phone's energy into a cone a few thousand miles wide when it hits the satellite is necessary even for short messages. You need to do much, much better than this for high bandwidth applications. GEO sats are also not a moving target; LEO sats are. That makes GEO slightly easier to point at, assuming you have a very wide beam which Satpaq does because it cannot possibly have a narrow one. Again, high bandwidth satellite applications cannot work with such sloppy pointing mechanisms, and that limitation exists because of physics and information theory. It's not because "we just don't have good enough technology yet." Beamforming techniques phones use to hit cell towers are not nearly good enough for satellites because satellites are so much farther away than cell towers. That means a satellite's transmitted energy is spread over a much wider area than a cell tower's is, and the ultra low power at which a phone transmits doesn't get a chance to spread out much before it hits the tower. You need a physically larger antenna when the thing you're pointing at is thousands of times farther away and you need to transmit with a lot more power. (Again, assuming you want the typical Youtube-style bandwidth cell phone users expect.)

lxgr 5y ago

Antenna gain is not binary: There's things in between laser pointers and lightbulbs. > Your aim has to be much better than the human musculoskeletal system is capable of. > You need a parabolic dish or phased array about the size of a pizza box (minimum) to boost the gain enough. No – there even is a very specific counterexample: https://satpaq.com/ https://satpaq.com/ I doubt that Apple would use that approach, though. If anything, I'd imagine that they'd use existing (for 802.11 and LTE) beamforming capabilities.

dreamcompiler 5y ago
Satpaq is yet another short message service. It seems to use a semi-directional antenna. It doesn't require exact pointing because the bandwidth is very low. You cannot surf the web with it and you certainly cannot upload Youtube videos with it. The only reason some pointing is required for Satpaq is that it uses GEO satellites which are a lot farther away than LEO, so concentrating most of the phone's energy into a cone a few thousand miles wide when it hits the satellite is necessary even for short messages. You need to do much, much better than this for high bandwidth applications. GEO sats are also not a moving target; LEO sats are. That makes GEO slightly easier to point at, assuming you have a very wide beam which Satpaq does because it cannot possibly have a narrow one. Again, high bandwidth satellite applications cannot work with such sloppy pointing mechanisms, and that limitation exists because of physics and information theory. It's not because "we just don't have good enough technology yet." Beamforming techniques phones use to hit cell towers are not nearly good enough for satellites because satellites are so much farther away than cell towers. That means a satellite's transmitted energy is spread over a much wider area than a cell tower's is, and the ultra low power at which a phone transmits doesn't get a chance to spread out much before it hits the tower. You need a physically larger antenna when the thing you're pointing at is thousands of times farther away and you need to transmit with a lot more power. (Again, assuming you want the typical Youtube-style bandwidth cell phone users expect.)