Wireless device RB751U includes a 2GHz 802.11b/g/n wireless device built in. It has PIF (Planar Inverted F-Shaped Antenna) type antennas (2.5dBi) built into the case, and one MMCX connector for an optional external antenna.

RB 751U has 3 built-in wireless antennas:

• Chain0
  • one antenna for TX
  • one antenna for RX

• Chain1
  • one antenna for TX/RX
  • MMCX connector for external antenna

To enable the external MMCX connector, set “antenna mode: antenna‐b” in RouterOS wireless settings, in the HT tab of Winbox. Note: enabling the external antenna disables the built-in Chain1 antenna.

• Use both chains for TX and RX.
• Chain0 tx and seperate antenna for rx.
• Chain1 tx/rx antenna.

  antenna-mode=ant-a
  ht-txchains=0,1
  ht-rxchains=0,1

• Disables internal antenna chain1.
• Disables tx/rx on chain0.

  antenna-mode=ant-b 
  ht-txchains=1
  ht-rxchains=1

• Disables internal antenna chain1.
• Enables tx/rx on chain0 (seperate antenna's).

  antenna-mode=ant-b 
  ht-txchains=0
  ht-rxchains=0

• Disables internal antenna's chain0.
• Enables tx/rx on chain1.

  antenna-mode=ant-a
  ht-txchains=1
  ht-rxchains=1

Maximum radiated power in The Netherlands is 100mW / 20dBm (e.i.r.p.).

• Real tx power = single chain power
• Total tx power = dual chain power

Example:
14dBm + 14dBm = 17dBm (logarithmic)
25mW + 25mW = 50mW

Antenna gain in dBi, used to calculate maximum transmit power according to country regulations.

• Antenna gain:

  antenna-gain=2

• Frequency mode:

  frequency-mode=regulatory-domain

• Country:

  country=netherlands

• TX power mode:

  tx-power-mode=default

• Show current TX powers:

  /interface wireless> monitor wlan1 once 
                   status: running-ap
                     band: 2ghz-n
                frequency: 2472MHz
        wireless-protocol: 802.11
              noise-floor: -109dBm
           overall-tx-ccq: 40%
       registered-clients: 0
    authenticated-clients: 0
              wmm-enabled: yes
        current-tx-powers: 1Mbps:14(14/17),2Mbps:14(14/17),5.5Mbps:14(14/17),11Mbps:14(14/17),6Mbps:14(14/17),
                           9Mbps:14(14/17),12Mbps:14(14/17),18Mbps:14(14/17),24Mbps:14(14/17),36Mbps:14(14/17),
                           48Mbps:14(14/17),54Mbps:14(14/17),HT20-0:14(14/17),HT20-1:14(14/17),HT20-2:14(14/17),
                           HT20-3:14(14/17),HT20-4:14(14/17),HT20-5:14(14/17),HT20-6:14(14/17),HT20-7:14(14/17),
                           HT40-0:15(15/18),HT40-1:15(15/18),HT40-2:15(15/18),HT40-3:15(15/18),HT40-4:15(15/18),
                           HT40-5:15(15/18),HT40-6:15(15/18),HT40-7:15(15/18)
      notify-external-fdb: no

• Band:

  band=2ghz-b/g/n

• Frequency:

  frequency=2472

• Offset 0:

  frequency-offset=0

• Possible widths: 10mhz, 20/40mhz-ht-above, 20/40mhz-ht-below, 20mhz, 40mhz-turbo, 5mhz

  channel-width=20/40mhz-ht-below

• Dynamic Frequency Selection off:

  dfs-mode=none