interesting article worth reading from home toys
Most "Home Automation" companies used to automatically include a repeater on any house that is 5,000 sq/ft or larger. It’s not that square footage is an absolute measure. Actually, we at ACT have successfully shot signal over 6 miles but I have also seen situations where I couldn’t get signal 20 feet across a room. Its not the square footage, it’s the impedance of the electrical distribution system. The relationship is this: the larger the system, the lower the impedance (usually). Another way to think of it is this: the larger the water pipe system, the more places the water has to go, the more likelihood of small leaks and the harder it is to keep the water pressure high.
[Link: hometoys.com]