I mean it has an antenna gain of 21dBi. How does that work in a European country (Poland) that has a legal limit of 20dBi max?

Is a outdoor device, and outdoor frequency from 5490 to 5710 is allowed in all E.U. @27dBm (2 stream, or @30dBm 1 stream)

But this can not work as AP, just as CPE/Client or a single-bridge mode... (until you do not buy Level 4+ license)

Then if you want to put it inside the house, go ahead
Indoor from 5170 to 5250 are allowed @23dBm (2 stream, or @26dBm 1 stream)

Only the limited portion Indoor from 5250 to 5330 is limited to @20dBm (2 stream, or @23dBm 1 stream)

Remember: on outdoor only from 5490 to 5710 are allowed

So, in conclusion, it is always illegal if you use it outside on indoor frequencies, the only allowed go from 5490 to 5710


EDIT: product error...

Is a outdoor device, and outdoor frequency from 5490 to 5710 is allowed in all E.U. @27dBm (2 stream, or @30dBm 1 stream)

RBLHG-2nD-XL is 2.4GHz only......

Ops... RBLHG-5HPnD-XL

When selecting correct country in wireless settings, ROS will know about maximum allowed EIRP of 20 dBm. Since antenna gain will be set to 21 dBi, ROS will be able to calculate correct maximum allowed Tx power - output from wireless power amplifier (at -1 dBm).

So yes, this unit is legal ... if user sets it up correctly.

-1dBm? So off?

0dBm = 1mW
-1dBm ~ 795µW = 0,795mW = 0,000795W...

Is a outdoor device, and outdoor frequency from 2402 to 2482 is allowed in all E.U. @20dBm (2 stream, or @23dBm 1 stream)

But this can not work as AP, just as CPE/Client or a single-bridge mode... (until you do not buy Level 4+ license)

Then if you want to put it inside the house, go ahead
Indoor from 2402 to 2482 are allowed at the same @20dBm (2 stream, or @23dBm 1 stream)

1 stream = 20MHz channel width
2 stream = 40MHz channel width
correct?

no... stream = stream, channel = channel...

I do not use "channel" word for not misunderstand channel size...

1 stream = use only vertical or horizonal polarization for transmit (use only one tx chain)
2 stream = use both (default, use both tx chain)

While I know my setting are correct and within legal limits how do you protect yourself when working around other antennas you don't have access to? I always remember this post from bpwl where he states that at a certain power output you can go blind. Where is the limit after which can the Tx power harm a person working around the antenna?

Well some of this is old info. Safe distance for 20dBm was documented as about 0.15 meter in EU . It would double for a 6dBm higher power .
Full math is available now: https://educateemf.com/what-is-a-safe-d ... fi-router/

Know your LOG math. 3dB is 0.3Bell or 0.30103 , that is the log10 value of 2. (10**0.30103= 2). (10**0.0=1) (10**2=100)
Notation
** or ^ or exp

0 dBm is 1 milliWatt , 3 dBm is 2 mW, 6dBm is 4 mW, 10 dBm is 10mW, 20 dBm is 100mW, 23 dBm is 200mW, 26dBm is 400 mW, 30 dBm is 1000mW

and then also
-3 dBm is 0.5mW, -10dBm is 0.1 mW or 100µW

So that -1 dBm is far from OFF, it is around 0.8 mW
Received signals are very weak compaired to the transmitted power . e.g. -86dBm ???

There must be a conversion table somewhere, to make it easy: Aargh yes .... https://www.rapidtables.com/convert/pow ... to_mW.html

We also learn from the presentations by Ron Touw, that the MT radio's do not obey settings below 2 dBm (seems to be the minimum level)

Remember in the ETSI/FCC regulations there are frequencies
- that are indoor only (forbidden outdoor, would disturb priority services)
- that are outdoor also (allowed everywhere)
- I don't know of any indoor only frequencies, no one to disturb there but yourselves