Hello,
Can someone tell me why a WiFi client disconnects from AP at relatively good signal?
There are no changes in the environment between the two during the trial period.
There is no access list rule defined.
cAPax wave2 / v7.11rc4
2GHz/n, channel auto, full allowed power (14dB reported, not explicitly set), antenna gain not set
According to the specification, the AP is expected to maintain the connection applying MCS7 or MCS0:
https://mikrotik.com/product/cap_ax
A relatively good signal is -60, -80…-75 is a poor or satisfactory signal.
The client starts looking for another access point when the signal strength is weaker than -68. MSC7 requires a signal stronger than -64
Sometimes they can already move above -68dB.
I have clients roaming when still being connected around -50dB.
And yes, everything lower then -70dB I wouldn’t classify as “relatively good signal”
Example from warehouse capsman installation.
Thank you both, your opinion is valuable to me.
I have configured many Mikrotik wifi devices and maintained them in production environment, so I am aware that not only Tx power is a factor, but also obstacles impacting the link quality (CCQ). If CCQ is high enough then established connection may stay stable even at -80dB, and -75dB then may seem as “good enough”:
If Green is “good” then why not the Orange be “relatively good”, well - “satisfactory”.
However, I don’t have much practice with “same SSID” setups. I had seen “radar” log message, but never seen “roamed” message. I indeed thought that when a connection to AP is established it is maintained until re-transmit threshold is reached. And here is the question - how do we know what is the threshold for MT and especially more - for non MT clients?
I don’t know as well, if scanning for better AP is possible while in a connection, or it is lost - as in initial or manual scan.
I really don’t believe that MT looks at signal power only when taking the decision for roaming. It wouldn’t be nice also, if you loose the connection because of dropping it for scanning, before a better AP was already found. And what means “better” - more powerful or with better CCQ, sometimes they may diverge.
How do you read the following message in AP’s log?:
B4:6C:60:2D:4D:74@wifi2 disconnected, connection lost, signal strength -66
Who initiated the disconnection - the client with the specified MAC? Why did it disconnect? Most probably not because the signal strength at MT AP was -66dB. May be the signal strength at the station device was poor - how poor, how do you know? I don’t have such information for our non MT device - an assembled LCD panel/tablet with AW859A radio chip. And there are no logs in it for such events.
So, I’ve came to the following conclusion:
If I don’t know why the non MT client disconnects, how will you or MT know? 
Sorry for the rushed post 
Discussing the case however was useful for me and I believe - for you too.
Meanwhile, I’ve found that the client has connected to the AP and wanted an IP address from DHCP server, which couldn’t be reached, because there was no such server configured in the AP and it was not connected to any other device. This might upset the client and lead it to the decision of disconnection, may be to try again later - and this should be answered by the device manufacturer and support team. As well as the power threshold of Rx signal. When I provided access to dhcp server, the disconnections stopped or at least became more rare.