R52N tx power

RouterOS Wireless Networking
1

Hi all!

I’m testing my first 11n installation, PtP with 411 and R52N, but I get some strange behaviors about tx-power.
I’ve set tx-power-mode=default, frequency-mode=regulatory-domain, country=italy and antenna-gain=17

If I do /interface wireless monitor wlan1 I get

      current-tx-powers: 6Mbps:4(4/7),9Mbps:4(4/7),12Mbps:4(4/7),
                         18Mbps:4(4/7),24Mbps:4(4/7),36Mbps:4(4/7),
                         48Mbps:4(4/7),54Mbps:4(4/7),HT20-0:4(4/7),
                         HT20-1:4(4/7),HT20-2:4(4/7),HT20-3:4(4/7),
                         HT20-4:4(4/7),HT20-5:4(4/7),HT20-6:4(4/7),
                         HT20-7:4(4/7),HT40-0:4(4/7),HT40-1:4(4/7),
                         HT40-2:4(4/7),HT40-3:4(4/7),HT40-4:4(4/7),
                         HT40-5:4(4/7),HT40-6:4(4/7),HT40-7:4(4/7)

and in winbox table I read tx-power=4dBm real-tx-power=4dBm and total-tx-power=7dBm for all datarates.

Could you please explain me what total-tx-power is and why neither tx-power + antenna-gain (=4+17=21) nor total-tx-power + antenna-gain (=7+17=24) is 27dBm as it should be?

Thanks!

2

Each chain on 802.11n adds 3dB to the tx and rx by improving signal reconstruction.

Check 802.11n on wikipedia.

3

ok, so with two chains 3dB are added, and this is why total-tx-power is greater then tx-power.

but why total-tx-power + antenna-gain is not equal to regulatory domain limit (27dBm)?

4

such information is written in the N cards eeeprom and we are using it for the regulatory domain settings - for tx-power limiting.