40mhz与20mhz都是目前无线局域网技术中的无线信号频带宽度，理论上讲，40Mhz相对于20Mhz拥有高一倍的信道宽带，理论数据传输率也高一倍；但从实际应用看，设置更高的频带宽度，有更大的几率和周边的wifi信号发生冲突，会对实际的数据传输率造成影响。
Bands vs Channels vs Streams. Wi-Fi uses three frequency bands, including 2.4GHz, 5GHz, and 6GHz.. Depending on the Wi-Fi standards and hardware, each band can have multiple channels of different widths, including 20MHz, 40MHz, 80MHz, 160Mhz, and 320MHz. The wider a channel is, the more bandwidth it has.
In most populated areas you shouldn't set 2.4ghz higher than 20mhz. You shouldn't use channels that overlap. In the US in most cases you only want channel 1,6 or 11. Wi-Fi Analyzer Tool vs Channelizer. Signal strength is important when troubleshooting and diagnosing Wi-Fi related issues, but it isn't the only factor to consider. Channels are an often overlooked aspect of Wi-Fi networking. If there is enough interference from nearby Wi-Fi networks then you can find yourself with poor performanceand reduced 4lGNNm.