How is a dual band router made

Mobile & Apps

Despite the dual-band devices, no 5 GHz WLAN is active

The riddle: You definitely want to connect your notebook to the dual-band router using the faster 5 GHz frequency. Because you need a high speed for video streaming to the laptop. That should actually work without any problems, because the notebook and router are not very far apart. Now check in the Windows network settings whether the 5 GHz connection currently exists. But the operating system indicates that the notebook is connected via 2.4 GHz. You disconnect the WiFi connection and reconnect the laptop to the router - but the problem does not change for the time being.

The solution: You actually did everything right. Because in this situation there is no 5 GHz WLAN that the notebook can connect to. This happens, for example, after restarting the router, which you either triggered yourself to install new firmware or to repair an unstable Internet connection. However, this problem can also occur after you have changed the WLAN settings in the router, for example when setting a specific radio channel.

Most dual-band routers switch off the 5 GHz frequency for a short time after restarting or changing the WLAN settings. This is required by law in the event that the router wants to use all radio channels above 5 GHz - including those in the frequency range from 5.26 GHz (channel 52). The so-called "primary users" of these frequencies also work there: These are services such as radar systems for the military, air traffic control or the weather service. These must not be disturbed during operation, which is why the router must first check whether a corresponding service is active in its vicinity after it has activated the 5 GHz WLAN.

In this case, you cannot do anything other than wait for the period of this test to then connect to the operational 5 GHz WLAN. Because if you change something in the router settings to shorten this waiting time, it starts all over again. Incidentally, this behavior does not occur with a router that lacks the DFS (Dynamic Frequency Selection) function, because it is only allowed to use the lower radio channels up to and including 48 over the 5 GHz frequency, which the radar systems do not use.

A dual-band-capable Fritzbox with Fritz-OS 7 or higher can shorten the waiting time by switching to a channel between 36 and 48 in the meantime in order to generally enable a connection via the 5 GHz frequency. After the waiting time has elapsed, it then changes back to the originally set higher channel.