Cannot change wifi channel, why?

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pzygmunt
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Have you tried to physically move MEW to another place? maybe there is some interference in the place of installation
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pzygmunt
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.. try shutting down the bridge and connecting mew-01 to the main router directly.
pisoiu
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Device cannot be moved, it is installed in a wallbox near some electrical distribution equipment. There are no interferences. Near the MEW there are 3 sonoff devices which works fine. Even better on lower channels than on channel 10. Moreover, the MEW have external antenna and all sonoff devices have internal PCB antennas, so in case of bad signal PCB antennas should work worse than devices with external antennas.
The bridging router is used to connect with ethernet to a computer without wifi. Its ssid is different than the main router ssid. All sonoff devices and MEW are always connected to main router only on its unique ssid.
I moved the network to channel 3. MEW seemed to work immediately after change, I was able to access it from android app. 15 minutes later I checked again and it was offline and it stayed this way since then.
Patryk
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What is the signal strength on channel 10 MEW-01 ???
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pisoiu
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Joined: Fri Jul 09, 2021 11:39 am

On channel 10 rssi is -82 (dBm I assume) and signal strength is 36%. There is some distance from router, which is in my house to those devices which are in the basement. I have poor propagation on that channel. MEW is ok because it has external antenna, but the other 3 sonoffs with internal PCB antenna are at their limit. Often they go offline. On channels 1-2-3 I have better conditions, when I change the network to those channels, sonoffs are stable, they do not go offline. But MEW is.
Patryk
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You have a very poor Wi-Fi network.
I know the MEW-01 has an antenna.
Sometimes it is enough to move the module a few centimeters and it is better or worse.
An external antenna does not always improve range.
If you manage to connect to channel 1, 2 or 3 what is the strength of WiFi ???
pisoiu
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Joined: Fri Jul 09, 2021 11:39 am

Yes, wifi signal is poor, but other devices with PCB antenna work fine.
You are right about moving the device, I know about phase variation in signal and its influence when the levels are low. But: 1. I tried with MEW antenna rotated in 3 different positions, same effect ; 2. my router have 7 antennas, I am quite sure it has antenna diversity ; 3. during tests, I moved the router with 20-30 cm, no effect
I cannot tell signal strength in lower channels, if I open the 'info' window, MEW immediately goes offline and I do not see any information.
On the other hand, I took the time to walk the routers through all the channels and see what happens. Starting from channel 7 and up, MEW starts working. Other sonoff devices work fine on all channels, however, their performance worsens on upper channels, they start to go offline then online periodically.
I will try to make some tests in the following days with a spectrum analyzer but my conclusion at this point is that either MEW's antenna or receiving circuit do not have a relatively flat response in all 2.4g band, it has a higher attenuation on lower channels than on uppers.
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pzygmunt
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I meant moving the device to another location temporarily as part of an experiment. MEW-01 has the same
wifi chip as it is in sonoff. The wifi drivers are also identical. I suspect there is something in your box overlapping the 2.4ghz band. You can also try to replace the MEW-01 with a new one at the manufacturer's.
Patryk
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Joined: Mon Jan 07, 2019 7:51 pm
Location: Rybnik

I checked my MEW-01.
I also show less on channel 1, 2 or 3 than on channel 10.
pisoiu
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Joined: Fri Jul 09, 2021 11:39 am

pzygmunt wrote: Sat Jul 10, 2021 8:53 pm I meant moving the device to another location temporarily as part of an experiment. MEW-01 has the same
wifi chip as it is in sonoff. The wifi drivers are also identical. I suspect there is something in your box overlapping the 2.4ghz band. You can also try to replace the MEW-01 with a new one at the manufacturer's.
It cannot be moved unfortunately. It means to disconnect it from grid, that involves too much work and leaving house without power.
I know it have the same chip and same drivers as sonoff, but this seem to be a pure RF design problem, not a software/firmware. Especially because Patryk confirm my suspicions (thank you). In his case, probably he is closer to the router , this is why his system works on lower channels. My weaker wifi signal puts me out of range when using lower channels. My apologies for accusing a problem related to channel 10, I initially tested only that one versus lower 1-2-3 channels which they did not worked. I did not imagined that the problem comes from an uneven response over the 2.4ghz band channels. Only after I tested all the channels I begun to see where the problem is.
I am curious how the RF part was designed. Did you followed the RF design recommendations of the ESP chip manufacturer or did you tested each channel with a RF signal generator and checked what the RSSI was?
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