Some believe that turning down the radio power to limit the range can mitigate hackers by forcing them to be in close physical proximity to the WiFi router.
The reality is that hackers can extend their reach to WiFi routers using antennas. In fact, there are reports of home-made antennas using Pringles or coffee cans extending the range by miles. Turning down the power will do little for mitigating hackers.
A good rule of thumb is to use only enough power as you require to reach all of your WiFi devices for their specific application. In a household setting or small office, it’s probably not really necessary to have WiFi access half-way down the block from the house or office.
Unfortunately, since WiFi is becoming so ubiquitous, WiFi signal interference is starting to become a problem. The simple answer is to simply amp up the volume—i.e. keep the transmission power high so the signal doesn’t get lost or buried in overlapping noise from other WiFi routers in the area.
The unfortunate aspect of all of this is something called aliasing. As more and more WiFi and other RF sources like cell phones, microwaves, and other signals are sent through the air, they can combine to appear to be higher frequency (and higher power) signals, which can interfere with other devices. There is even emerging debate on the health impact of WiFi and other RF electromagnetic fields.