Will the optical modem WiFi and router WiFi interfere with each other if they are turned on at the same time? The channel crashed and the internet speed was cut in half. I won’t believe it until I tested it with the app.

My cousin came to me after installing broadband at home and said he had something he couldn't figure out.: The broadband has been upgraded from 100M to 300M, and he also bought a new Xiaomi AX3000T router, but his mobile phone speed test is still the same, and he still spins in circles while watching videos at night. The broadband master came to test it and plugged the optical modem port directly into the laptop and measured over 320 MB. He said the broadband was fine and left. The machines are all good and the money has been spent, but the speed just can’t be improved.

I didn't do anything else that night when I went to his house, so I asked him to install an app on his phone to check the WiFi channel. After opening it and scanning, the problem was immediately revealed - the WiFi that comes with ChinaNet and the Xiaomi router's WiFi, 2.4G, are all crowded on channel 6. The two signals are on the same frequency and channel, and they are stepping on each other, so no one can run fast. The two WiFis are very close to each other and are both on the TV cabinet in the living room, which means two people are shouting at the same time in the same room.

This problem is not uncommon, but it is particularly easy to complain as "the broadband is slow", or to blame the new router for not working. I wrote down clearly what I had checked out that day and how I later handled it for the other two companies.

Figure it out first: How can two WiFis "fight"?」

The 2.4G frequency band is only so wide, and there are only three channels that don’t really fight with each other: 1, 6, and 11 (I won’t go into the reasons. If you want to go into more detail, you can read what I wrote before How to check WiFi channel interference ). As long as two devices fall on the same channel, they have to queue up and send signals.: You have to wait when I send it, and I have to shut up when you send it. This is not a matter of slower Internet speed, but a matter of blocking each other's road in half.

If the optical modem's WiFi and the router's WiFi channels are staggered, for example, the optical modem is at 1 and the router is at 11, they can actually get along fine. The bad thing is that the "automatic channels" of the two devices each have their own calculations. Optical modem firmware usually nails a channel before leaving the factory, or moves it only once every half a day. ； The router's automatic channel will jump to whichever channel is available around it. Some models will jump by themselves in the middle of the night. Choose one of the two "automatic" ones, and the probability of a crash is not low at all - my cousin's car has the optical modem fixed at 6, Xiaomi automatically scanned it and found that 6 is the emptyest (it can't see the background noise of the optical modem), and it also fell on 6.

There is a more hidden layer: There are many channels in the 5G frequency band, and the probability of crashes is much smaller. 90% of this problem lies in 2.4G. The sweeping machines, smart sockets, and old TV boxes at home can only connect to 2.4G. Therefore, the symptom is often "the mobile phone speed test is OK, but at night the whole family's smart devices collectively disconnect" - 2.4G is squeezed into porridge by two WiFis.

Diagnosed in one minute: Just glance at it on your phone and you will know whether it has been hit or not.

Install a WiFi analyzer app on your Android phone (search for "WiFi analyzer", the free one will suffice). When you open it, you will see a channel occupancy map. Each WiFi has a parabola, and the horizontal axis is the channel number. Look at two things:

• For the WiFi on optical modem that starts with ChinaNet/CMCC, what channel number does the apex of the parabola fall on?
• What is the channel number of the WiFi of your router?

If two vertices are next to each other (within a difference of 2, such as a 6 and a 7), they are interfering with each other. ； If the difference is more than 5 (a 1 and a 6, a 6 and an 11), it is basically no problem. The iPhone doesn’t have such an intuitive app, so I just remember a simple method.: Connect to your home WiFi, look at the channel number displayed in the router's backend or app, and then find a way to check the channel in the Lightmao backend (how to enter the Lightmao backend, and who is in charge of ChinaNet? I wrote an article How to turn off WiFi on Telecom optical modem , the backend entrance is universal).

The results of the scan at my cousin’s house that night: optical modem ChinaNet-XXXX is on channel 6, Xiaomi's 2.4G is also on channel 6, and there are two neighboring WiFi's on channel 6 and 7. It is equivalent to four parabolas stacked on top of each other, and 2.4G is completely out of sight.

Two ways to solve: Stagger the channel, or simply turn off optical modem WiFi

The relationship between optical modem WiFi and router WiFi, if you think about one thing clearly, you will not be entangled.: The home already has its own router, and the optical modem WiFi is a "redundant third network" for this home. Staggering the channels means that the two networks do not interfere with each other. Turning off the optical modem WiFi directly reduces one network. I dealt with three families. They took different paths and each had their own reasons.

Let’s first talk about how to stagger the channels. The router is easy to handle, enter 192.168.31.1 (Xiaomi) or its own brand backend, change the 2.4G channel from "automatic" to manual selection. If the modem is 6, you will choose 1, if the modem is 1, you will choose 11. Anyway, the stagger is more than 5. Don't worry about "what to do if the surroundings become crowded in the future" when selecting a channel by hand. The home environment will not change much in half a year. If you manually watch it once, it will automatically jump randomly for half a year - I have also experienced the incident of Xiaomi's automatic channel jumping in the middle of the night and the collective loss of contact with the sweeping machine. I wrote it in How to choose the channel of Xiaomi router Inside.

On the optical modem side, the channel generally cannot be selected by itself (when a normal account enters the backend, the channel drop-down box is mostly gray), so the initiative for staggering lies with the router. I really want to change the super password for the optical modem channel, but it’s not worth bothering with the super password for this matter - just stagger the direction and let the router do it.

Let's talk about closing this road. I have written a special tutorial on how to turn off optical modem WiFi. A normal useradmin account is enough. Both the web backend and the Xiaoyi Guanjia App will work. But there is one thing that must be done before closing: Find out who is currently hanging on optical modem WiFi. Check the WiFi device list in the background. If the TV box and old camera are still hanging on ChinaNet, let them change the connection to the router's WiFi one by one, and then turn them off after all migrations are completed. Otherwise, when you turn it off, the equipment hanging on it will be disconnected directly. The next day, the elderly at home will not be able to turn on the TV, and they will have to worry again.

Turn off optical modem WiFi, there are two finishing touches don’t miss

First, the problem of mobile phones being "sticky". Some mobile phones (my old Huawei is like this) have very good memories. After the optical modem WiFi is turned off, there will still be an afterimage of the signal, or it will automatically connect back as soon as the signal appears. Delete the ChinaNet record on your phone and select "Forget this network". Regarding why mobile phones are always stuck on WiFi with poor signal, and why the number of signal bands and network speed are not the same thing, I am here WiFi signal is full but speed is very slow The reason has been revealed.

Second, take a speed test that night after closing. Take your phone and stand next to the router to test, and then go to the farthest room to test. After I turned off the optical modem WiFi at my cousin's house and manually selected the Xiaomi channel to 11, his mobile phone in the bedroom went from more than 70 MB to nearly 290 MB - the first time the 300M broadband ran close to full speed. His original words were, "The broadband promotion in the half year before co-writing was in vain."

By the way, some people are afraid that turning off optical modem WiFi will affect the remote maintenance of the broadband master, don’t be afraid. The operator Guanguangmao uses the TR069 line, which has nothing to do with WiFi. It should be remote as usual. What is this line? ITMS and TR-069 Wrote in. There is one thing to note: Some optical modem will be pushed back by ITMS in the middle of the night after their WiFi is turned off. The next day, they find that ChinaNet has been fully resurrected. Just go to the background and turn it off again. Don't panic.

Which people really don’t need to move?

Not all families with the coexistence of "optical modem WiFi + router WiFi" are sick. You can leave the three situations alone:

First, the optical modem is in a weak current box and the router is in the living room. They are far away from each other and there is a wall. The 2.4G signal is already so weak that it has no lethality when it reaches the other party. Whether the channel collides with another car will have little impact. Second, there are no old devices that can only use 2.4G at home. Everything in the whole family is connected to 5G. No one uses 2.4G, and it is useless to use it. Third, the broadband itself is within 100 Mbit/s, and the demand is there, even if it is half blocked, it will not be felt.

On the other hand, if more than two of the following signals appear, it is time to check according to the above process.: I installed a new router at home but the internet speed has not changed. ； Smart devices collectively disconnected and reconnected at night ； The mobile phone is obviously connected to the router, but the WiFi is sometimes fast and slow. ； The optical modem and the router are placed together or very close to each other. After checking for half an hour, the answer is clear. Don’t let two WiFis that collide eat up your broadband money in vain.