My mother lives in a area where the cell-phone signal is very weak.
Typically I can get only one mark on the phone field strength meter. That
forces me to go outside the house in order to have a reasonable chance of
completing a call (of course only if the weather permits). I have only basic
understanding of antennas, so I am asking this forum if the following idea
is feasible.

I am planning to build (or buy) a 850 MHz Yagi antenna (14 dB gain) to be
installed on the outside and pointing towards the signal strongest
direction. The boosted signal would be transmitted through a balun and a low
loss 75 ohm coax cable to the inside of the house terminating to a 1/4
wavelength 75 ohm antenna stub. Is this feasible? Could I get perhaps a 10bB
signal boost inside the house by means of this arrangement?

TIA
Gene