I am far away from the modem router and have a very weak signal. There is no other wifi signal, so could you please tell me which Channel Width (20mhz or 40mhz) and channel (2.412ghz or 2.484ghz) is better?
I know these settings are not so important and there is some physical way to increase it, but I just want increase a much as possible!
I agree with Alex Atkinson that you probably need an extender - or either move your accesspoint or get a second one ( see How can I get the same SSID for multiple access points? )
To answer your question you will probably see increased range on 20 MHz compared to 40 Mhz - specifically a 3 dB stronger signal. This is because going from 20 to 40 Mhz means spreading your output-power into a larger frequency band - You maintain the same output-power but you basically maintain two seperate wifi-channels. This means dividing your power between two frequency bands, half for each, which is consistent with a 3 dB decrease.
Waves attenuate more quickly at higher frequencies, so 2.412ghz is better. That said, you, being human, won't see any difference between the two. It would take a sensitive piece of equipment to measure any effective difference between the two even in a clean environment.
On channel width. More width = greater throughput. It has no impact whatsoever on range.
You'll need a WiFi extender.
