According to http://wiki.freifunk-hannover.de/Fonera_mit_OLSR (german Freifunk wiki page on the Fonera), the antenna settings are set to diversity under Kamikaze on the Fonera by default. It also uses the wrong antenna, bypassing the external one
I added an english version of the wiki entry to the OpenWRT Fonera wiki page. After trying the change I definitely saw more accesspoints around my box with wlanconfig ath0 list ap. Could someone with more knowledge on the topic please verify this?