Hi guys.

I have tplink 1043nd powered by openwrt 15.05.1 I configured two SSIDs a81m for empliyee and a81m-guets for visitors.

my config looks like bellow:

/etc/config/wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option channel '11'
        option hwmode '11g'
        option path 'platform/qca955x_wmac'
        option country 'US'
        option htmode 'HT40-'
        option txpower '20'
        option noscan '1'
        option distance '10'

config wifi-iface
        option device 'radio0'
        option ssid 'a81m'
        option mode 'ap'
        option encryption 'psk2+ccmp'
        option key 'censored'
        option macfilter 'deny'
        list maclist '1C:AF:F7:D6:82:C3'
        option network 'wan lan'

config wifi-iface
option device 'radio0'
option mode 'ap'
option hidden '0'
option encryption 'psk2+ccmp'
option key 'censored'
option bgscan '0'
option wds '0'
option macfilter 'none'
option ssid 'a81m-guest'
option network 'vlan12'
option channel '5'
option disabled '0'
option isolate '1'

but I'm still see via wireless scanned network a81m-guest broadcasring via channel 11 not 5 seleccted above.
it looks like wifi-iface inherit settings from wifi-device?
how to force different SSID to use diferrent channels?

Thank you.

You have only one radio, you can only tune into one channel.

so rule is:
one radio can broadcast any SSID via one (same) channel?
that device has 2.4 ghz and two SSID configured. it's only one way force second SSID to use different chanel is agregate it with another radio interface or move second SSID to 5.4 ghz?

Is it correct assuption?

One radio can only tune into a single channel at a time.
Some wireless chipsets can create multiple AP interfaces (with different SSIDs) on the same channel, this is usually limited to around 4-8 at most.
These days most of the better routers come with two radios, one exclusively for 2.4 GHz, the other exclusively for 5 GHz.
The market is slowly seeing some highend devices with three radios, one in the 2.4 GHz band, two in the 5 GHz band to aid with meshing or repeating (or to divide the large 5 GHz band into a low (non-DFS sub-band and DFS based high sub-band with a much larger bandwidth).

It is correct that some chipset manufacturers are experimenting with multi-channel operations (partially as a side effect of large bandwidth channels), but those efforts seem to have stalled (or are simply too difficult/ expensive for the market).
None of these have left laboratories or reached the enduser market so far.

I see. Thank you.