We stay in a campground all winter. The campground has free WiFi. The signal is OK until more and more campers arrive then we fail to connect.(there is a lot of tin in camper sides) The campground is unresponsive about improving their signal. Our laptop has built-in wireless card. We have tried other removable cards without any improvement. As it is, sometimes we can connect and sometimes not.
The laptop does not need to be moved about so is there some sort of card and external antenna that could be mounted on the camper roof to give line-of-sight improvement in reception. I have seen removable cards with attached external antenna but is there a card with a connection that can be hard wired to an remote antenna? I would be willing to disable the built-in card and use a card such as I described if something exists. Any other suggestions? Thank you.

you need something like the ,Hawking hiGain Antenna

Or if you're feeling handy you can make one yourself out of a Pringles can. I haven't actually done this yet, but it's supposed to improve your reception as much as 3x (in a single direction).

DIY Wireless Update at http://wireless.binarywolf.com has what you are looking for.