On Tue, Jul 22, 2008 at 1:34 PM, Craig Jungers <crjungers_at_gmail.com> wrote: > On Tue, Jul 22, 2008 at 1:10 PM, Bob Myers <qajaqbob_at_gmail.com> wrote: >> >> However, for some reason the coverage maps fade out before Hawaii. >> Not sure why that is for a satellite based device. >> >> http://www.findmespot.com/ExploreSPOT/Coverage.aspx > > It looks as though they are using geostationary satellites; and only 5 of > them with specific directivity on the antennas (or perhaps two receivers > with directional antennas on only 3 satellites). It does look like that from the coverage map, but it seems odd to me that they would use geostationary satellites rather than low orbit satellites for transmission - geostationary orbit is a LONG way up there to transmit from a little handheld device. I find that hard to believe. Hmm, I think this page explains it (found on a search about SPOT, linked from this page http://www.globalcomsatphone.com/spot/coverage.html): http://www.globalcomsatphone.com/globalstar/info.html Globalstar satellite phone service is delivered thought 48 Low-Earth-Orbiting Satellites providing both voice and data services. The Globalstar LEO constellation is only 700 miles from earth... Globalstar's (Bent-Pipe Technology) allow the call to be first beamed up to the satellite and then retransmitted to a relatively close gateway. The call is then sent through to its call destination through land-line or cellular networks. The Globalstar Gateway carries out all the processing and switching of the calls rather than the satellite itself. This improves the reliability of the call delivery. So I guess they need a "gateway" somewhere nearby to relay the signal from the LEO satellites, and that's why coverage doesn't work in areas where they haven't installed a "gateway" yet, such as southern India, southern Africa, and over parts of the open oceans. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Tue Jul 22 2008 - 14:14:16 PDT
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