Subtleties when working with wifi 5Ghz

Question

Android

There is RT-N66U
ipad 2
samsung p6800
nexus 4 The
router distributes Wi-Fi at a frequency of 2.4GHz and 5GHz. Nexus and Samsung see only the 2.4GHz band, Ipad sees perfectly and works at a frequency of 5GHz.
Help, where should I dig? I don't even have any idea why this is happening.
here are the settings
https://www.dropbox.com/s/k3dz8dkvuawa6vj/%D0%A1%D...
https://www.dropbox.com/s/umxjidrl32y0q1n/%D0%A1%D...

Answer 1

Most likely the devices have different country codes. Different channels are available for different countries.
I changed the country code on my router:

$ ssh 192.168.0.1 
 
 
ASUSWRT RT-AC66U_3.0.0.4 Tue Sep 25 02:42:17 UTC 2012
[email protected](none):/tmp/home/root# nvram show | grep -E 'ccode|regrev|regulation|wl[0-9]_country|wl[0-9]_reg_mode' | sort
size: 38607 bytes (26929 left)
pci/1/1/ccode=EU
pci/1/1/regrev=15
pci/2/1/ccode=EU
pci/2/1/regrev=15
regulation_domain=EU
regulation_domain_5G=EU
wl0_country_code=EU
wl0_country_rev=15
wl0_reg_mode=off
wl1_country_code=EU
wl1_country_rev=15
wl1_reg_mode=off
[email protected](none):/tmp/home/root# nvram set pci/1/1/ccode=CN
[email protected](none):/tmp/home/root# nvram set pci/1/1/regrev=5
[email protected](none):/tmp/home/root# nvram set pci/2/1/ccode=CN
[email protected](none):/tmp/home/root# nvram set pci/2/1/regrev=5
[email protected](none):/tmp/home/root# nvram set regulation_domain=CN
[email protected](none):/tmp/home/root# nvram set regulation_domain_5G=CN
[email protected](none):/tmp/home/root# nvram set wl0_country_code=CN
[email protected](none):/tmp/home/root# nvram set wl0_country_rev=5
[email protected](none):/tmp/home/root# nvram set wl1_country_code=CN
[email protected](none):/tmp/home/root# nvram set wl1_country_rev=5
[email protected](none):/tmp/home/root# nvram show | grep -E 'ccode|regrev|regulation|wl[0-9]_country|wl[0-9]_reg_mode' | sort 
size: 38599 bytes (26937 left)
pci/1/1/ccode=CN
pci/1/1/regrev=5
pci/2/1/ccode=CN
pci/2/1/regrev=5
regulation_domain=CN
regulation_domain_5G=CN
wl0_country_code=CN
wl0_country_rev=5
wl0_reg_mode=off
wl1_country_code=CN
wl1_country_rev=5
wl1_reg_mode=off
[email protected](none):/tmp/home/root# nvram commit 
[email protected](none):/tmp/home/root# reboot

Answer 2

Change the channel in the router to another one.

Answer 3

Most likely the Nexus and Samsung simply do not know how to 5GHz

Answer 4

Remove the space from the SSID.

Answer 5

I have Nexus 4 and Nexus 5 point RT-N56U. True with alternative firmware. Both quietly work with both frequencies. Something in the settings of the router seems to be wrong.