I suppose an AN/FLR9 in the back yard is out of the question
That's for HFDF operations, don't think it would do well with microwaves...
http://en.wikipedia.org/wiki/AN/FLR-9But seriously, you'd really need something like this to actually boost your cell signal:
http://www.alternativewireless.com/cellular-antennas/wilson-vehicle-wireless-repeaters.html