Basebox2 connectivty issue with changing tx rx chain

i have 2 unit basebox 2…with diffrent antenas…i have speed issue mostly through that devices..today i chacked deeply when i change tx rx chain ..like tx 0 1 and rx 0 1 i have lowe speed through this device…when i select tx chain 1 and rx chain 0 1 i have no issue in speed…and there is starange issue…when i select tx chain0 and rx chain1 then i got signal but wirless not connected with my laptop… plz help me in this issue