Four quick questions about adding wireless AP

[zetsui]

1. If someone can't access my network because of a password on the wireless itself, do I have to really set something beyond the default password?
2. If I have my default router with a wireless AP on channel 11, would setting my new AP on channel 11 on a different floor strengethen/heighten that signal, or should I just use a different channel with a stronger signal?
3. Are all 802.11N enabled laptop/network cards dual band by default? Does a 802.11n enabled device have any advantages of running on an AC router? If not, should I leave the 5ghz on, but disable AC network mode for any reason?
4. When I make my Router WD AC 1300 http://www.amazon.com/AC1300-Dual-Router-Wireless-Accelerate/dp/B00A14ZUIM go into AP mode, does that ONLY make my wired network wireless OR say I unplug the wired internet, does it also make it into a WIRELESS AP (provided it has the same SSID as my main router/can get its signal)? Or do I have to specifically buy a 'wireless' AP?

 

[byza]

1. You should change it anyway as anyone you do give access to or if someone manages to hack the router somehow can change the settings pretty easily if it is the default password. It's really up to you what you think the risk of this happening is, but it's a pretty easy thing to change.
2. You should usually try to find channels that have the least interference.
3. Yes all N cards can pick up both the 5Ghz and 2.4Ghz frequencies. There is no need to disable AC.
4. I'm a little confused as to what you are trying to do here. I think what you are trying to do is turn it into an extender? If so you'd have to read the manual,some routers can, some can't. So you are aware, using it as an extender (or any extender) will halve the bandwidth. For DSL this doesn't really matter for internet speed but will slow down transfers (streaming) over the wireless network.

 

[bill001g]

You can make any router into a AP. The key thing you have to do is turn off the DHCP server. So just unplugging internet does not make it into a AP since the DHCP server is still active. You of course need 1 device with DHCP on so if you have no internet connection you could run DHCP on a AP even though generally a AP does not do that function.

Pretty much what a router that has a setting to put the device into AP mode is doing turning off the DHCP and converting the WAN port into a LAN port.

A actual device you buy that is called a AP generally also has the added feature of being able to be powered over the ethernet cable. Many times the best place for a wireless AP does not have a power connection so PoE is important especially in business installations.