4 ms·

Yep, https://www.cnet.com/news/new-wi-fi-distance-record-382-kilometers/ https://www.cnet.com/news/new-wi-fi-distance-record-382-kilo... . If you have big enoug

Yep, https://www.cnet.com/news/new-wi-fi-distance-record-382-kilometers/ https://www.cnet.com/news/new-wi-fi-distance-record-382-kilo... . If you have big enough antena and state of the art amplifiers, 500km is not unbelievable and that is high enough to orbit a satellite (for example ISS is at about 405km now). Plus, you have only about 100km of atmosphere (I might be wrong here).

jacquesm 9y ago
It's not that simple, those point-to-point links are done with both highly directional antennae at both ends. You'd need to deal with Doppler (the satellite is moving pretty quickly, and likely in a relatively complex path relative to the transmitter), attenuation because of rainfall and other atmospheric effects, polarization, non-directional transmitter antenna and the effect of likely having 1000's of transmitters of roughly the same kind in the footprint of the satellite antenna. It isn't impossible, but 'Yep' is a bit of a shortcut, and if they pull this off it would be quite the technological feat. It also would mean that if this is possible that you wouldn't need anything special to implement SpaceX's vision of ubiquitous internet using LEO satellites, the antenna tech for that is quite exotic and requires a roof mounted structure, something that almost no WiFi transmitter has. So those WiFi distance records are not at all on the same level as picking up a single WiFi signal from space, the one requires cooperation on both sides, the other has to do everything on one end (but obviously with a larger budget and some really clever people behind it). If you've ever done such a long haul WiFi link then you'll know how hard it is to line up the dishes and how easy it is to lose the connection due to wind, vibration or water in the atmosphere.
- jjoonathan 9y ago
  They've got billions of dollars to dump into a ginormous phased array with nearly perfect acoustic isolation, no gravity or kids tripping over wires to mess up an absurdly long baseline, custom software stack, custom steering loop, and probably even custom silicon. I'd expect them to do substantially better than some dudes in the desert with glorified cookware. Especially when it comes to the steering loop, because if there's one thing phased arrays are really, really good at, that's it.
  - planteen 9y ago
    Why would there be nearly perfect acoustic isolation? Spacecraft have jitter from spinning reaction wheels or CMGs.
  - jacquesm 9y ago
    Money does not trump physical law.

jacquesm 9y ago

It's not that simple, those point-to-point links are done with both highly directional antennae at both ends. You'd need to deal with Doppler (the satellite is moving pretty quickly, and likely in a relatively complex path relative to the transmitter), attenuation because of rainfall and other atmospheric effects, polarization, non-directional transmitter antenna and the effect of likely having 1000's of transmitters of roughly the same kind in the footprint of the satellite antenna. It isn't impossible, but 'Yep' is a bit of a shortcut, and if they pull this off it would be quite the technological feat. It also would mean that if this is possible that you wouldn't need anything special to implement SpaceX's vision of ubiquitous internet using LEO satellites, the antenna tech for that is quite exotic and requires a roof mounted structure, something that almost no WiFi transmitter has. So those WiFi distance records are not at all on the same level as picking up a single WiFi signal from space, the one requires cooperation on both sides, the other has to do everything on one end (but obviously with a larger budget and some really clever people behind it). If you've ever done such a long haul WiFi link then you'll know how hard it is to line up the dishes and how easy it is to lose the connection due to wind, vibration or water in the atmosphere.

jjoonathan 9y ago
They've got billions of dollars to dump into a ginormous phased array with nearly perfect acoustic isolation, no gravity or kids tripping over wires to mess up an absurdly long baseline, custom software stack, custom steering loop, and probably even custom silicon. I'd expect them to do substantially better than some dudes in the desert with glorified cookware. Especially when it comes to the steering loop, because if there's one thing phased arrays are really, really good at, that's it.
- planteen 9y ago
  Why would there be nearly perfect acoustic isolation? Spacecraft have jitter from spinning reaction wheels or CMGs.
- jacquesm 9y ago
  Money does not trump physical law.