Dusan,
To build on what Kdisc98 mentioned...it depends. The "show ap monitor scan-info ap-name <name of ap>" command will show you how long an access point remains on each channel: http://www.arubanetworks.com/techdocs/ArubaOS_64_Web_Help/Web_Help_Index.htm#ArubaFrameStyles/New_WIP/TotalWatch_Administratio.htm
How long an Air Monitor stays on each channel (the dwell time) depends on what kind of channel it is:
Here are the default dwell times for an Air Monitor (all-reg-domain setting):
Active Channel (channel with clients on it) - 500 milliseconds
Regulatory domain channels with no clients - 250 milliseconds
Regulatory domain channels outside of current regulatory domain - 200 milliseconds
Rare Channels - 100 milliseconds - (only active if scan mode is set to rare)
DOS or channel with a rogue access point - 500 milliseconds
(7240) #show ap monitor scan-info ap-name Office-225
WIF Scanning State: wifi0: 9c:1c:12:90:59:50
---------------------------------------------
Parameter Value
--------- -----
Probe Type am
Phy Type 80211a-VHT-80
Scan Mode all-reg-domain
Scan Channel yes
Disable Scanning no
RegDomain Scan Completed yes
DOS Channel Count 0
Current Channel 161E
Current Scan Channel 161E
Current Channel Index 27
Current Scan Start Milli Tick 162479200
Current Dwell Time 250
Current Scan Type all-reg-domain
Scan-Type-Info
---------------
Info-Type Active Reg-domain All-reg-domain Rare DOS
--------- ------ ---------- -------------- ---- ---
Dwell Times 500 250 200 100 500
Last Scan Channel 36E 161E 46E 0 0
#7240