hello, i have mount one ap two days ago and for 24 hour it was ok until yestoday midnight signal was to low, i have checked today both sectors have 1 line at laptop signal metter (message:signal strength very low) at distance of 30metter clear line of sight. my config is rb4333 with two r52h, no overpower .default settings antena gain 0 tx default etc,only two clients connected to antena me, and a friend .
yestoday was a clear day no rain no storm etc. i dont know is it a card problem? i have bought this cards one year ago from mt. but i havent used does they have any warranty? i have about 14 pcs and all are r52h . i am afraid for the other cards if they will have same problems , my rb433 are version3.6 should i downgrade them to stable version? i have bought them with this version installed.
Replace it with new card. If signal strength is back - something wrong with that wireless card ( PA, diversity switch ).
thank you. in fact i have exchage it sudenly this morning and everything is ok but i am curious what happend to that card , i have 14 pcs stock and i am afraid for the rest. i have also made misurement to diversity ic versus ground and compared to a new card the values are similar .i dont think is diversity ic prob. i will try to fit to another rb for test. and will post result. do you know where to find parts for repair ex diversity ic pa ic , this are simple to exchange , i have worked with celular repairment and i have all tools to do that, just for creating idea of what is dameged . i think it need calibrate after that 
It seems it’s PA problem SST11LP12 if you are on 5GHz or SST12LP14 if you use 2,4GHz. Something like factory defective IC. If card warranty is only few weeks over I think you can try write rma@mikrotik.com with problem explanation.
i think too, i have tryed with a rb in a short distance i can connect pppoe also but signal is 50% at 3 metter dist, so is PA.
If i use a small tx power that default settings could i controll this card-failure in the future?
I have one that failed at a client location. I set the tx-power to 17 and it worked fine.
Don’t know if it will work in your case, but it’s worth a try when it happens.