WiFi Tx speed not stable

[myname70]

With 10.11 the WiFi tx rate drops to 800 kbps from 1170 kbps.. With latest 10.10.4 versions - the rate was rock stable at 1300 kbps

 

[nihoso]

Just experienced the same after the 10.11.2 update. Don't know whether it was happening on other versions too. Sometimes due to the drops in tx rate, the music over airplay is stuttering.

My Macbook is connected via an airport express and the distance is below a metre.