They do have a data sheet, their DA340 cable supposedly loses some 8.5db per hundred feet at 1900MHz, while their DA440 loses only 5.8db. (The DA340 loses twice as much signal as the better quality cable, which I'd bet is way thicker and heavier.)
The 4db cable loss isn't bad, but it still means they are losing more than 1/2 the incoming signal in the cable. Still...and without running all the numbers...as a system it probably has enough gain to be useful.
There are limits in the software
used in the cellular system which look at the signal delay times for any given call, and even if you can work a tower, the tower is told to drop you if you are something like 32 miles away from it. The system assumes there will always be another tower closer than that--or, you really don't matter to them anyway.