We have replaced now every week the Atheros AR5212 card. The problem is as soon as the weather comes up the signals drop down to -90 and the clients was on -60.We have ground the antenna witch is a 15dbi omni and we have earth on the RB532 as well and still it is only the omni witch is giving us problems. What can be done to solve it but not replacing the antenna with a sector? Can it be a faulty antenna or damage cabling? All connectors are properly sealed.
Thanks
I think there are a few threads about this already , some omnis will blow cm9s because there is nothing to bleed away excess power on the omni or th e radiocard . Just try another type of omni.
just try to rod your omni, there was very long thread about how to protect your radios that are connected to omni antenna form blowing.
got it 
here is the link the thread
http://forum.mikrotik.com//viewtopic.php?t=9734&start=0&postdays=0&postorder=asc&highlight=ligtning+omni+rod
Other tips:
A) Use omnis w/DC grounded radiators.
B) Stop using cards w/diversity switches.
Hi found the problem. The glue witch hold the housing to the bracket came loose so it the weather comes up h2o go in to the antenna and the swr went up and damage the card. Have rebuilt the site again to day and have installed sectors on the site.