5.xGhz antenna don't work on that freq. but does on 2,4Ghz

RouterOS Wireless Networking
10

I have the same problem! My RB532 with R52 card and 5.7-5.8Ghz, 13dbi omni does not function at 5.7-5.8Ghz but works at 2.4Ghz range. These are new equipment freshly order directly from MikroTik.

See http://forum.mikrotik.com/t/rb532-wont-run-on-5-8ghz/8575/1 for details