E5336’s Wi-Fi signal is always weak?

1).When E5336 using it’s battery power, in order to save energy for longer run-time E5336 will lower down its transmit power ,so Wi-Fi signal is weaker compare with powered by USB or power adapter. Connect E5336 to power adapter or with USB cable to a running computer’s USB port will enhance E5336’s Wi-Fi signal strength. 
2). Keep E5336 at least 3 to 6 feet away from other electrical devices which may create RF signal and cause interference (for example, microwave oven, TVs, cordless/cellular phones, baby monitors or wireless speakers). If you needn’t using any of those devices when you want to connect Internet, please turn it off. 
3).Wi-Fi covered range of E5336 is according to its power supply mode and its using environment. In Idea clear square area the Wi-Fi covered range of E5336 showed below: 
    Use power adapter: 100m(328ft) 
    Use USB cable connect: 20m (66ft) 
    Use battery supply: 10m (33ft) 
4).In actual use Wi-Fi covered range maybe different from idea square area, it decided by the environment you use. The closer to E5336, the stronger Wi-Fi signal you get. And every obstacle (walls, ceilings, furniture) between your device and E5336 may decrease Wi-Fi signal strength. Move your device closer to E5336 can avoid obstacles and improve Wi-Fi signal. 
5).Change the Wi-Fi channel to fix one other than auto (you can try the available channel one by one and select the channel with best signal strength)