Wierd problem with atheros card's??

i have now try to configure the mikrotik, like 1 mounth and nothing…

my problem is that i just can get my d-link dwl-g520 (Atheros AR5213) to work more then 2 MB and i don’t now why..

i try to change:
my computer (i used amd 3.0 with 1 GB ram)
my antena (homemade biquad,orginal antena)
my cable,and nothing
the distance is like 5 metar,on one site mikrotik ap bridge and other site linux and windows client and i just can get to work more than 2 MB

i try’d 2 change chanells but only get worse i buyd a new card with the same chipset,and nothing…

can somebody help me this is the last place i trying.
do i have some security “on” or what i just can configure that it can work.


pls help
thnx,sorry for so bad english