If the antenna used says 6db on it does that mean the antenna gain should be set at 6? I am trying to improve the range of my router as it doesn’t perform very well.
Entering the antenna gain against a wireless interface usually makes matters worse as this is used to ensure you keep within the legal EIRP for your location. Set TX Power to manual or anntena gain to 0 to get the highest output from your card, but beware you might then be transmitting at illegal power levels.
If you have a problem with range try buying a higher gain antenna. A 6dB antenna won’t go far even with a high power card.
Try using the Link Possibility Calculator in the Wiki to determine what gain antenna you need for the distance you’re trying to bridge.
http://www.mikrotik.com/test_link.php
One tip, make sure you enter receiver sensitivity as negative numbers, all other numbers must be positive.
thank you. dumb question. is there a limit to high big of an antenna i can put on this thing?
also when you say set transmit level to manually, do you mean to put it at 100%? is it not their by default?
There is no theoretical limit to the gain of what antenna you can attach, only a practical one. The higher the gain of an antenna, the narrower the angle it covers.
A 0db antenna covers an area roughly spherical, between 2dB and 15db you have the option of omni-directional or sector. Omni-directional antennae cover a area roughly doughnut shaped, getting squashed flatter the higher the gain. Sector antennae cover a smaller and smaller arc the higher the gain.
You can get antennae with gains of 26dB and more, but you usually have to turn down the power of the wireless in order to keep within legal limits, e.g. in the UK legal EIRP @ 2.4GHz is 20dBi, so ignoring cable loss using a 26dBi antenna would require the wireless to be set to -6db. In the US higher power limits apply, max EIRP @ 2.4GHz is 36dBi (assuming you’re using a narrow beam angle antenna), so the wireless card could be set to 10dB. Don’t think that you can just buy a high power card and high gain antenna and set both to Max, you’d likely be exceeding 52dBi which I’m fairly certain is illegal pretty much everywhere.
In wireless options set TX power to manual, then in the TX power tab select “card rates” and then enter the max value for your card, e.g. 100mW = 20dB, 200mW = 23dB. However, as said before you have to determine what the max EIRP is for your location, the TX power of the wireless plus the gain of your antenna minus any cables losses must not exceed the legal EIRP otherwise you will interfere with other users and likely end up with some enforcement officer turning up on your doorstep.
Regards
Chris Macneill
I live out in the middle of nowhere. actually, just south of nowhere. i doubt anybody will be monitoring my wireless activities. but I’ll keep that mind, thanks.
Hi!
I would like to keep my wireless as weak as possible.
What setting should I put in antenna power and tx-power?
Thank you
Hi
I doubt if it’s still necessary. However,
it depends on your board. But putting the antenn gain as high as possible and your tx power as low as possible will make your wirelles coverag as weak as possible.
Set your country regulatory domain and laborate with antenna gain value. The higher gain you set the lower tx power will be applied.
To clarify once more, since this bit of information got lost in the discussion …
setting the antenna gain number in RouterOS settings has only one use - reduction of TX power to match the total output power with the local regulations. If you don’t care about that, do not enter anything in this setting, because it will allow the device to output full power.
But teodorch wanted to reduce the tx power…
sorry, I was answering the OP
So setting the antenna gain does not focus the radiation beam?
How can it possibly do that? 
Antenna gain (and thus a radiation pattern) is a physical characteristic dependant on antenna’s geometry, and can’t be changed unless an antenna can change it’s geometry on the go 
Surely you’re right as far as traditional antennae go. With modern beam-forming antennae (physically they are 2D array of simple antennae with appropriate number of lower-powered Tx elements which act as a phase-array antenna) it is actually possible to change focus of radiation beam(s), but mostly that’s not done.
What usually is done is to have a few constant-focus narrow beams that change directions to follow stations movement … and a single wide beam for transmitting beacon and to start off communication with a new (or previously idle) station.
That counts for
unless an antenna can change it’s geometry on the go >
Not in the verbatim sense of meaning. Phase array doesn’t change geometry of antenna, it changes Tx timing of individual (tiny) dipoles and ditto for Rx (where constructive resonance of all Rx elements contributes to higher overall Rx signal from one direction) … but yes, the net effect is similar, antenna pattern changes.
Well, in the verbatim sense of meaning antenna array is not a single antenna, as you already wrote yourself 
Modern access points can transmit simultanously to different users on multiple patterns of the same antenna by adjusting the phase of the different elements of an array.
(MU-MIMO)
So … if I have cAP ac and want to cover as match is possible what gain should I set?