With 700 and 800 MHz. there are several ways to improve reception. These bands work a bit differently than others though.
Most of the time more elevation works best, but 700 and 800 is more sensitive to coax loss. For these reasons I suggest that you try swapping out the coax first, then raise the antenna if you still need more oomph.
I suggest that you use RG-6, preferably the quad-shield type intended for satellite TV use. The higher quality RG-6 sold at Radio Shack, Lowes etc. should work just fine. Your antenna might already have an F-Connector on it, if not then use a single adaptor to match. (Don't use multiple adaptors, it introduces too much loss.) Use a single adaptor at the radio end, you might have to order F-BNC adaptors if you can't find them locally.
You also might want to try an amp. I have had great luck with a Wingard TV pre-amp. Don't bother with those cheapo TV amps, get a good one. Also, the Stridsberg 800 MHz. active multicoupler has an amp built-in that works great on 800.
