20MHz corresponds to 65M bandwidth, with good penetration and long transmission distance (about 100 m). 40MHz corresponds to 150M bandwidth, with poor penetration and short transmission distance (about 50m). The 300M of your router means that the transmission rate (maximum transmission rate) of your router is 300Mbps, also known as network speed.
How to set the band bandwidth:
1 First, take the router out of its package and connect it with an external power supply.
2. Home routers usually have five WAN interfaces. 1 is the interface for connecting WAN, which is on one side alone. The larger one has four [5 ~ 8】LAN interfaces. The wireless router can be used as a wired router for 4 computers. A connecting cable that connects a WAN port to an external network. Usually, this cable is an RJ45 connector that can be plugged into the WAN port of a router.
3. First, you need to log in to the router to set it up. There are two ways to log in to the router: the computer logs in wirelessly from wifi or wired from LAN port [twisted pair network cable is required]. Wired login, the usual IP address is:192.168.0.1. Wireless doesn't need an address. Generally, the login user name of the router is admin, and the password is also admin.