heh....
That 18dbi antenna is waaaaaaay overkill...it's designed for ptp wireless links with ranges in the
kilometers....
I run a 14dbi 'directional waveguide antenna' for certain applications :
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I can pick up signals from your average "wrt" type wifi router from 10 Km away.
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Most high performance antennae use 'type-N' connectors......you'll need adapters to get to rp-sma........
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In your case , I'd suggest something like this :
http://www.smc.com/files/AJ/ds_HMANT_6.pdf
It's a 6dbi antenna , native rp-sma connector , and it's nice and small.