weird location + past war.

say your desert is at some high or low latitude where there just generally aren't a lot of people. the satellite communication network flies at mid to low inclinations where all the people live, but your remote desert colony is out of the way and no/few satellites fly overhead. They COULD pay for a comm sat with a higher inclination orbit, but if they are a poor colony that may not be in the cards for many years. 

GEO sats kind of ruin that answer... maybe there's a lot of debris in orbit from a war in the past that make GEO orbits a mess, and all current comm sats are in LEO. Count MEO in this category too for you Molniya fans, all that junk will smash those too. The debris and space junk in the lower orbit all fell back (takes 20 years or less for lower orbits due to atmospheric drag) but the higher altitude orbits are basically unusable. In that scenario the answer above works to isolate your desert colony.