How far are wireless LAN effective?

Answer 1

Under ideal conditions, about 200 feet. In the real world, it varies considerably. In some installations, I have gotten a strong signal from a router as far as 120 feet away. In others, there has been so much interference or environmental blockage of the signal that I couldn't detect it when only 20 feet away. The best way to figure out what the range will be is to get a router and see what happens. Also, be aware that moving a router even a few inches or feet one direction or another could make a huge difference in the functionality.

Major household causes of interference are high-power electrical lines (in other words, the 120-volt power cables) running through the various walls of one's home, air circulation duct work, and metal Plumbing. All these will easily break apart the weak 50mW signal strength of a 2.4GHz wireless LAN signal and do even more damage to the even less reilient 5GHz signal of modern use.

If you are not sure how to evaluate your environment (whether home or office), then get in touch with a local computer store that does network installations. Many such firms will do tests at no charge and let you know where you could expect to have the weakest signals as well as how to help eliminate them.