hi
i have rb433+xr2+it elite sectore in b/g mode and ap-bridge and all other things is default

but when any device connected to it the tx ccq = about 12 but rx ccq= 100

whats the reason.the link quality is very bad and maximum download that we tested is 250 kb/s

a few days a go i test r52hn and have this problem

What are the signal strenghts?

Export and print wireless interface settings of both AP and client so forum can take a look.

signal is very good between -40 to -55 at tx , rx
rx ccq is very good tx ccq is very bad

signal is very good between -40 to -55 at tx , rx
rx ccq is very good tx ccq is very bad

If tx CCQ is bad (when date is transported. If not CCQ's drop low anyway) it could be the ´other´ end has lots of interference of other signals.
Run a scan on both ends to see if you have other strong signals in the same or nearby band.