Is there any values for TX Power i want to decrease the power of the radio.
With which values should i play to decrease my TX-Power?
I’ve found tx values from other vendors ,are there same as MikroTik?
Thanks
When you are operating with the setting “regulatory - domain” (as is always advisable) and you want
to decrease the TX power the easiest way to do so is to set a higher value in the antenna gain (in advanced mode).
The unit will compute the maximum EiRP using this larger antenna gain and will reduce the TX power to compensate.
E.g. antenna gain 10 more → 10 dB less TX power.
At the moment i’m using RB951ui-2hnd.
So about antenna gain i found in the specification about this router, it say “Antenna gain dBi for 2.4 GH.” That is the max tx power that this Rb can produce? Also i’m using regulatory domain
Have you got document about antenna gain 10 more → 10 dB less TX power., like more examples?
Thanks a lot
When you set the antenna gain to 12.5dB you will have 10dB less power than when you set it to 2.5dB.
I’m afraid there is no document explaining the obvious.
Simplified:
A (theoretically supposed) ideal omnidirectional antenna would spread the power evenly to all directions (it is called “isotropic” radiation, or a spheric radiation diagram).
An antenna with a gain concentrates the power into only a part of the sphere (if simplified again to make it easier to imagine, into a cone) thus raising the power density in that cone.
In the receiving direction the mechansim is the same.
Most regulators do not set a limit to the transmit power sent to the antenna but to the resulting power density. As the latter is not easy to express, the “EIRP” (which means "equivalent to isotropically radiated power) power value is stated instead. So if your antenna concentrates all the power into e.g. a cone which occupies only 1/4 of the sphere, the power density will be 4 times or 6 dB higher there. So to stay within the regulation limit, you must decrease the transmitted power by 6 dB.
To make it simple for the users, Mikrotik has internal tables with EIRP limits for the individual regulatory domains (countries). So by choosing the country you choose the maximum EIRP power allowed in that country. And RouterOS subtracts from it the antenna gain and sets the result as Tx power.
That’s why you can control the Tx power the way described by @pe1chl.
Even more obvious (because I’m also fairly new to concepts like EiRP):
MikroTik isn’t just giving you direct control over radio power, like a lot of other 3rd party firmwares do. To do this might violate regulatory controls. They don’t want to do this. And you shouldn’t do it. And since you’re decreasing your power you probably won’t 
But they let you do it anyway through an indirect method.
EiRP (the number that is controlled by regulation) is a calculated value and it includes antenna gain.
These guys are telling you that you can manipulate TX power by changing antenna gain.
If you tell the firmware that your antenna is much better (higher gain) than it is, it will then reduce TX power accordingly, and that’s how you reduce TX power.
What is there to violate…when we want do decrease TX level. (which is good idea having multiple APs in “small” area)
If I want to violate regulations…what happens when I configure my antenna as if it does -20 dB gain?
The possible violation was mentioned to explain the background of how it is done
Of course you cannot violate anything by decreasing power, and of course if you tell the RouterBoard that you’ve got a bad antenna (or long cable to it) while you actually haven’t, the RouterBoard increases power accordingly (up to the physical limit of the transmitter) and the EIRP thus exceeds the limit.
It is just that indicating the antenna gain and letting RouterOS calculate and set the needed Tx power from it and the regional EIRP limit retrieved from a table is more convenient for most users than having to calculate the needed Tx power manually from the same values.
Decreasing the power below the maximum permitted limit is required by much less users, that’s all.
It will probably not accept that value.
But when you have a directional antenna connected or integrated into the AP, it is possible to violate regulations by setting a gain of 0dB or another value lower than the actual gain.
Note that all manufacturers point out that it is the responsibility of the owner/operator to obey local regulations.
However, the regulatory authorities are not naive either, and as you can see more and more limitations on wireless settings are becoming enforced instead of user-settable.
Personally, I would not be surprised when at some point the gain setting would get a lower limit for at least the APs with integrated antenna.
What is the proper way to do this with current RouterOS 6.47.7? “antenna-gain” is missing since 6.47. I did not find a recommended way to decrese the TX-power of my Access Points.
Proper way to set TX power is by setting TX power 
On the WLAN interface, enable ‘advanced mode’ and select the Tx Power tab. Here you can set the Tx Power Mode and corresponding power.
Don’t forget to configure country code first.
As you can see my prediction from Jan 25, 2018 became reality! Now it is no longer possible to set the gain to a fake value.
However, the implementation has bugs. When you had an older version than 6.47 and set a fake gain there (like 0) and now you have upgraded to 6.47 and above, you can no longer change the gain to an acceptable value in winbox and webfig but the error message that the gain is unacceptable still appears when you try to change the country code and other settings in that screen.
You will need to go to commandline mode to change the gain before you can set anything else.
I currently have a RB4011 and several cap ACs in a home environment. What I did in the past was to increase antenna gain of the interfaces in the caps. One idea was to reduce 2,4Ghz by 7dbm compared to 5Ghz, the other idea was to reduce the interfaces to the lowest required value to make the Wifi work best. I used frequency mode regulatory-domain and the correct country as suggested by several people.
So now I have to reset my cap ACs by setting antenna-gain to 2 (2,4Ghz) and 3 (5Ghz) in the CLI. After that I shall use Tx Power Mode “all-rates-fixed” and a manual Tx Power for each interface? I tried this, but the dbm-value of the interface does not change. Is it because the interfaces are managed by CAPsMAN? How do I configure each interface on my own and still be able to use CAPsMAN?
I added channels with the corresponding TX Power setting. Might be a bit hard in a big environment, but for my three accesspoints it works great!
/caps-man channel