That's wild, I had no idea cellular was line-of-sight.I have one at the ranch for inside the hangar (metal building) with it off there is zero cell service inside! On; 5 bars
If you are asking about a mobile one to boost your cell service when off-road, remember that cellular frequencies are strictly line of sight.... if you are in a valley or ravine, and there is no tower that can "see" you, it doesn't matter how much power you throw at it, it still doesn't work.
I use Garmin inReach for those times