Hello
Maybe I missed something in the specifications, in which case I’m sorry
The question is why all devices are connected in “65Mbps-20MHz / 1S” instead of “130Mbps-20MHz / 2S” in TX Rate
In RX Rate all was fine ( “130Mbps-20MHz/2S” )
Example of client is “ASUS PCE-AC55BT B1” based on “Intel AC-8260”
For “2S” you need 2 chains, or 2 antenna’s. Antenna-mode is not on all Mkt AP’s. To get to the default in Winbox there should be a little down arrow to clear the input.
The RB751 2nD has 2 chains, so it should work.
antenna-mode (ant-a | ant-b | rxa-txb | txa-rxb; Default: )
Select antenna to use for transmitting and for receiving
ant-a - use only ‘a’ antenna
ant-b - use only ‘b’ antenna
txa-rxb - use antenna ‘a’ for transmitting, antenna ‘b’ for receiving
rxa-txb - use antenna ‘b’ for transmitting, antenna ‘a’ for receiving
Thanks for the advices
Here is my “/interface wireless export”
# may/23/2020 10:05:32 by RouterOS 6.46.6
# software id = 6QTQ-UTUA
#
# model = 751U-2HnD
# serial number = 412E025F15A1
/interface wireless
set [ find default-name=wlan1 ] adaptive-noise-immunity=ap-and-client-mode band=2ghz-onlyn bridge-mode=disabled country=ukraine disabled=no disconnect-timeout=5s distance=indoors frequency=2462 hw-protection-mode=rts-cts installation=indoor \
keepalive-frames=disabled mode=ap-bridge multicast-buffering=disabled multicast-helper=disabled preamble-mode=short ssid=MikroTik wireless-protocol=802.11 wps-mode=disabled
/interface wireless nstreme
set wlan1 enable-polling=no
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/interface wireless access-list
add allow-signal-out-of-range=5s interface=wlan1 signal-range=-81..120 time=0s-1d,sun,mon,tue,wed,thu,fri,sat vlan-mode=no-tag
add allow-signal-out-of-range=5s authentication=no forwarding=no interface=wlan1 signal-range=-120..-82 time=0s-1d,sun,mon,tue,wed,thu,fri,sat vlan-mode=no-tag
I don’t see a “chain” field on it
But in Winbox gui on the “HT” tab I marked both “chain” ( I am attaching a screenshot_1 )
I also don’t have “default” choice in “Antenna mode” field ( I am attaching a screenshot_1 )
And I tested all 4 available modes, the situation has not changed
BTW, when device is just connected, in “Registration” table I can see something like “26 Mbps-20Mhz/2S” but then it became 65Mbps in 1S ( I am attaching an example on screenshot_2 )
Your AP has the full 2x2 (2S) capability correctly configured and it is used. The “interface rate selector” selects the interface rate it can work in. The top is MCS15 (actually 2X2 MCS7) , one step lower is MCS14 (2X2 MCS6) … if there are still problems in transmitting a packet the “interface rate selector” will step further down. The algoritm is brand dependend. Also if one of the chains is weak then only 1S can be choosen. The registration screen (if you select ‘detail mode’ in the right down arrow) will show the signal strength per channel, and many more. A low CCQ will make the rate selector step down, a good CCQ will make it step up. (That step up/down process can be unstable). The number of retransmits can be calculated from RX and TX packets versus RX and TX HW packets. That is how CCQ and P-throughput is calculated.
If the connection drops to 1S, then either the signal has become too weak, or there are so many reflections, refractions, scattering and interference of the signal that the receiver cannot separate the 2 streams.
To have the registration information as text ,you can use the CLI command
“interface wireless registration print stats”
