Thank you both for your replies.But i just noticed in the ath man i can't see my atheros card(ar5424) in the supported chips and the link provided by the man
http://customerproducts.atheros.com/...ts/default.asp for an up to date list won't open!Also I found this:
http://www.daemonforums.org/showthread.php?t=3404 so i think installing the kernel won't fix the problem! :/ I think i 'll check buy another card which is supported!
edit:Any suggestions of external cards supported by openbsd 4.9 ?