3 ms·
It's pretty likely that you need a particular frequency band for this enormous distance.
by Tepix 3y ago
It's pretty likely that you need a particular frequency band for this enormous distance.
- lxgr 3y agoNo, the frequencies used are pretty much in the middle of commonly used terrestrial bands. The specified non-terrestrial 5G bands are in the MSS part of the radio spectrum: Apple's solution uses Globalstar, where the phone transmits on 2.5 GHz and receives on 1.6 GHz (I think that must be the newly-specified 5G band n254). Iridium uses 1.6 GHz in both directions (no 5G band assigned); Inmarsat is on 1.5 and 1.6 GHz (band n255), and Echostar (formerly Terrestar), which is used by the Motorola Defy, uses frequences around 2.0 and 2.2 GHz (band n256). Since there's pretty much always a line of sight to the satellite, the usual rule of "lower frequency means better propagation" doesn't really apply, and in a vacuum, all frequencies propagate equally.
- wkat4242 3y agoThe path to the satellite is mostly not in a vacuum which is why some frequencies are not suitable. For example around 2.4Ghz is an absorption frequency of water which is why this freq is popular in microwave ovens as well (and thus why they cause interference with WiFi). This is why the 1.6Ghz band is so popular, as it's the least affected. I would imagine 2.5Ghz being not so ideal but Globalstar is a pretty basic repeater system so I imagine they had to separate the input and output frequencies a lot to avoid huge filter systems to avoid it causing interference on itself.