if at all possible, mount the Accesspoint (if your using one) right up at the antenna and run ethernet cable back to your network (plus power or power over ethernet).
If you are using cards, like I think you mentioned, then the run of coax should be as short as possible. I run around 15m of LMR400 up to a 8dbi omni antenna and although I see many access points, the signal levels are well down from when I stumbled on the roof with my laptop and a short length of cable.
Stay away from RG213, it is not designed for much 500MHz and the loss is very high /100m above 1000 MHz. Although, RG213, is better than nothing for a meter of so if mounting equipment at the antenna.
have fun
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