weird Wi-Fi problem

[Octane]

I'm at a friends place and my android tablet doesn't see his AP. My android phone detects it as does his iPad. However his windows laptop
doesn't either. Signal strength is not the issue because we are next his AP and we can see other AP's. Why would the AP be invisible to some devices only? I'm puzzled. Interested to hear your thoughts.
Thx
Octane

[nxb]

One possibility is that the AP is set to operate on a 5GHz channel (Channel 36+).

If that's the case, only devices that support operation on channels in both the 2.4GHz and 5GHz bands will see the AP. The iPad is capable of seeing AP's configured for 5GHz operation so that's one data point that matches what you see.

Of course this theory only makes sense if the AP is capable of being configured to operate on both the 2.4GHz and 5GHz bands. If it is one of those, set it up to work on a 2.4GHz channel (channels 1-11 but best to use channels 1, 6 or 11). All Wi-Fi devices should see it then.

Background: Wi-Fi operates on two radio bands - one at 2.4GHz and the other at 5GHz. All devices support operation in the 2.4GHz band. Higher end devices will support both.

[A A Gruntpuddock]

Perhaps they are set to run on different frequencies?

List of WLAN channels - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/List_of_WLAN_channels)

[llondel]

Further to that, given that different parts of the world have a different number of channels in the 2.4GHz band, it's possible that the AP and the working devices are using a channel that the other devices aren't even looking at because they're set for the wrong country.

[Octane]

Thanks for that. Will look into it.
Cheers
Octane

[JimR]

I had this problem with my home WiFi. In my case it was due to the type of encryption my router was set for (and which I had to modify).
My smartphone etc has no problem with WPA2 etc, but my poor old laptop will only accept WEP which is of course not very secure, and certainly not recommended. Unfortunately, I cannot update my laptop hardware to accept the newer protocols. I don't want to change it because, other than that it works just great!

[boguing]

I have a Zyxel AMG1302 router which does this with an Android tablet. All Windows pcs see the router, but on two occasions the Android refused to see it.

It's not an Android problem as such, because it will see other routers appear and disappear as they are switched on and off.

This has happened twice in six months of daily use. On the first occasion I reset the router through it's firmware. When it happened yesterday I tried a simple paperclip reset, which cured it. Either will set everything back to defaults, which is a minor bore if it's just the SSID and password, more so if it's set up to do clever streaming etc.

[MacBoero]

I resolved an issue at a local cafe that was getting complaints from some of its customers unable to use its wifi. When I went observe the problem I had a Apple MacBook Pro and an iPhone with me. And sure enough neither could see the network. I rebooted the macBook into Windows 7 and this could see the network.

The problem was the SSID. The cafe had asked for the SSID to be the name of the cafe which included an accent over one of the characters. Turns out Mac OS, iOS and some other handheld devices were not happy with the accented character. Change the character for an un-accented one and the problem was fixed.

Not suggesting this is definitely the problem you might be having, but is a simple thing to check for whilst you are looking.