signal Strength, CCQ, and TX/RX

Dear Mikrotik Gurus

I provide internet to customers via pppoe server.

I have a RB433 with Atheros AR5413 card on it, and the lan port is connected to the pppoe server.The Wlan card is set to 2GHz B/G mode , WDS static with Ignore SSID checked. The clients are working fine, signal strength is good as well as CCQ and TX/RX.

Later I installed RB751 that has Atheros 11N on it. Same setting are made, signal strength are good, but CCQ and TX/RX keep going up and down, and the users routers keep going in and out of the pppoe server, eventhough cliens are connected to the RB751.

How I can get stable CCQ and TX/RX on RB751 and keep users connected to pppoe server?

Thank you

You could LOCK (check only into software) from the minimum STABLE MCS and BELOW your AP.
What signal strengths are you getting?