Exclamation [Q] Low Wi-Fi reception

I am currently experiencing horribly low wifi reception. Sitting right next to the router the signal jumps from full to low randomly and it doesn't catch any wifi in spots where other devices do. What do I do? Same happened in 4.3 and 4.4.2.
Samsung Galaxy S
Semaphore Kernel

Samsung Galaxy SIII
CyanogenMod 11

HTC One Max
Stock untill I get bored