Problem:
I'm trying to more deeply understand the /interface wireless 'antenna-gain=' setting with regards to what should be set to maximize signal strength in relation to the hardware specifications (i.e., LHG 5). In searching the forums and I found one similar post (viewtopic.php?f=7&t=150889). I've also read the Mikrotik FAQ(https://wiki.mikrotik.com/wiki/Manual:Wireless_FAQ) and Mikrotik Manual:Interface/Wireless (https://wiki.mikrotik.com/wiki/Manual:I ... e/Wireless), but none of these resources answer the question in much detail regarding what should be the recommended setting to both stay within Country Regulations and not transmit more power than the hardware specifications state to prevent damage to wireless cards. I understand 'tx-power-mode' set to anything other than default runs the risk of damage with improper settings, but I've also been advised by a 3rd party consultant that improper 'antenna-gain' can also damage the wireless card over time if set to 0, which I've questioned, but haven't found a clear explanation enough to believe it.

For example, a 'Mikrotik LHG 5' specs show Antenna gain dBi for 5 GHz to be '24.5' (https://mikrotik.com/product/RBLHG-5nD), which I'm led to assume this must be the value provided to 'antenna-gain=' for this hardware and should not be left set to 0 as seen with a default RouterOS configuration.

*Side note: '24.5' is not a valid value for the 'antenna-gain=' setting within '/interface wireless' unless you round up or down 25 or 24 DBi.

Example Config:
/interface wireless
set [ find default-name=wlan1 ] adaptive-noise-immunity=ap-and-client-mode \
allow-sharedkey=no ampdu-priorities=0,1,2,3,4,5,6,7 amsdu-limit=8192 amsdu-threshold=\
8192 antenna-gain=0 area="" arp=enabled arp-timeout=auto band=5ghz-a/n \
basic-rates-a/g=6Mbps bridge-mode=enabled channel-width=20/40mhz-XX compression=no \
country="united states3" default-ap-tx-limit=0 default-authentication=yes \
default-client-tx-limit=0 default-forwarding=yes disable-running-check=no disabled=no \
disconnect-timeout=3s distance=dynamic frame-lifetime=0 frequency=auto frequency-mode=\
regulatory-domain frequency-offset=0 guard-interval=any hide-ssid=no ht-basic-mcs=\
mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7 ht-supported-mcs="mcs-0,mcs-1,mcs-2,mcs\
-3,mcs-4,mcs-5,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-13,mcs-14,mcs-15,mcs-16\
,mcs-17,mcs-18,mcs-19,mcs-20,mcs-21,mcs-22,mcs-23" hw-fragmentation-threshold=disabled \
hw-protection-mode=cts-to-self hw-protection-threshold=0 hw-retries=7 installation=\
outdoor interworking-profile=disabled keepalive-frames=enabled l2mtu=1600 mac-address=\
XXXXXXXXX max-station-count=2007 mode=bridge mtu=1500 multicast-buffering=\
enabled multicast-helper=default name=wlan1 noise-floor-threshold=default \
nv2-cell-radius=30 nv2-downlink-ratio=50 nv2-mode=dynamic-downlink \
nv2-noise-floor-offset=default nv2-preshared-key="" nv2-qos=default nv2-queue-count=2 \
nv2-security=disabled nv2-sync-secret="" on-fail-retry-time=100ms preamble-mode=both \
radio-name=XXXXXXX rate-selection=advanced rate-set=default rx-chains=0,1 \
scan-list=default secondary-channel="" security-profile=default ssid=XXXXXXXX \
station-bridge-clone-mac=00:00:00:00:00:00 station-roaming=enabled \
supported-rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps \
tdma-period-size=2 tx-chains=0,1 tx-power-mode=default update-stats-interval=disabled \
vlan-id=1 vlan-mode=no-tag wds-cost-range=50-150 wds-default-bridge=none \
wds-default-cost=100 wds-ignore-ssid=no wds-mode=disabled wireless-protocol=nv2 \
wmm-support=disabled wps-mode=disabled

Questions:
- Is it possible to damage the wireless card of Mikrotik PTP/PTMP hardware if the 'antenna-gain=0' if the Country and Frequency Mode are set appropriately (e.g., united states3/regulatory-domain)?
- If not, then is damage possible if the Country is undefined and Frequency-Mode is set to 'manual-txpower' with 'antenna-gain=0'?

-----------------------------------------
- Any thoughts are greatly appreciated to fill in the gaps of what I may be missing or not understanding. I also hope answers may help resolve confusion for others seeking understand this as well in the community.

In the wireless tab change the country to your country.

Then select regulatory domain in order to be limited to the frequency channels available for your country and also for the max Tx power you are allowed to use...

Finally, insert the antenna's gain according to the specifications so that the max transmit power, eirp, can be calculated...the higher the gain you use the lower the Tx power value will be so that you stay inside the regulation limits...

Zacharias, thanks for the response. Per the example config, I'm aware how to set Country and Frequency Mode, but my question really has more to do about concerns with leaving the antenna-gain set to 0. Is there anywhere in Mikrotik documentation that actually describes that the antenna-gain should match the DBi of the specs sheet?

The meaning of antenna-gain is solely to alliw unit to calv+culate correct EIRP as @Zacharias already wrote. And units are dBi which is custommary unit for antenna gain (I haven't seen it written anywhere in MT documents, but this is common radio knowledge).

If you don't play with Tx power table, then leaving antenna gain set to 0 won't hurt hardware, ROS will automatically back-off Tx power for modes which require different Tx profile. Leaving antenna gain set to 0 will only make your station illegal due to excessive EIRP.

Leaving antenna gain set to 0 will only make your station illegal due to excessive EIRP.

@mkx even if he lets Gain to 0 but country is set to regulatory domain then again he will stay within limits... so why is it illegal?

As antennas in small RBs, for example, are usually 2dBi, your AP will be 2dBm stronger than allowed in your country.

Setting antenna gain at a non 0 value will tell the router to subtract that gain to stay with country regulation.

Sent from my cell phone. Sorry for the errors.

As antennas in small RBs, for example, are usually 2dBi, your AP will be 2dBm stronger than allowed in your country.

Oh yes... how i missed that
Although i know we should provide the real gain... my mistake...

The responses and clarification are much appreciated. This discussion has definitely helped me understand much more about the antenna-gain setting and what it does, but it seems like you'd need to manually calculate EIRP in order to figure out if you're over the legal limit depending on the wireless card unless it's assumed all wireless cards output would meet the dBm limit with the tx-power-mode set to default. Also, it's interesting to note that Mikrotik would not code the setting in the RouterOS firmware for device models that have internal or non-replaceable antennas so people with less understanding may avoid illegal dBm using the quickset feature with regards to having the appropriate antenna-gain set. Now I'm curious about finding resources to understand more about calculating EIRP, but I think that is beyond the scope of the the current forum topic.

Thank you all for your knowledge and time!

AFAIK there is no need to specify it for devices with integrated antenna.

AFAIK there is no need to specify it for devices with integrated antenna.

Any reference in the wiki for that?

Actually I would like to know the dBm shows in datasheet is EIRP(Board+antenna gain) or just dBm from ROS? For example cAP ac, it has 26dBm for both 2.4G and 5G, but it never tell either it's 24+2 or 26+2

EIRP (dbm) = Output power - cable/connector losses + Antenna Gain

I cant be sure but i believe the datasheet refers to the total radiated power, so the Antenna's Gain is included...

AFAIK there is no need to specify it for devices with integrated antenna.

This would be very interesting to verify if true since most of the devices I work with have an integrated antenna.

AFAIK there is no need to specify it for devices with integrated antenna.

This would be very interesting to verify if true since most of the devices I work with have an integrated antenna.

There is no reference in the wiki for that... so....
According to the manual in the Antenna-gain you specify the value of the antenna's gain... It doesnt say that if its intergrated let it to 0...

Is there any trusty source for that?

AFAIK there is no need to specify it for devices with integrated antenna.

Any reference in the wiki for that?

I was talking about changes made in this ROS version:
viewtopic.php?f=21&t=144949

If I understand this right, in theory, if frequency mode is set to regulatory domain and you have a correct country setting, then ROS won't let you set antenna gain value lower than needed for EIRP to stay inside country regulations. And as some of the users wrote, that was the exact situation for them - there was some minimal value depending on the country.
However I tried to do so myself now, and I haven't found any country setting, that won't let me set antenna gain to zero.

So either there were some other changes that I missed (for example making 0 a new default setting, meaning maximum TX-power for your country, so that you can only lower the TX-power setting the higher gain), or it just don't work for some reason.

To sum up:

The device itself for sure "knows" the gain of its integrated antennas.
You can check it yourself: And it is clear, that from ROS 6.43.11 version if in regulatory-domain mode the device won't let you fall out of your country regulations somehow.
That's what the change was about.

The only thing that is not clear for me - what does antenna gain setting represent after all:
Is it "real gain" = "hw gain" + user set "antenna gain"?
Or is it "real gain" = max("hw gain", user set "antenna gain").

xvo in the forum topic you posted someone said that gain exists as a value in the device and you can see it if in terminal type: interface wireless info hw-info wlan1

I tested it, in the result you can see that the antenna's gain exist even if you haven't configured it...

So, if the device knows its antenna's gain, then why should i provide it as well?

Since it knows that its antenna gain is lets say 2 dbi, then why i can change it to 0,1,2,3,4,5 ... ?

A few versions back (don't remember when exactly) MT implemented minimum antenna gain setting for models with fixed/internal antennae. E.g. if built-in antennae have 2dBi gain, then it's not possible to set this parameter to 0 or 1 ... but it is posible to set it higher, e.g. to 10. As ROS will reduce Tx power to maintain max EIRP within country regulations, setting high antenna gain (where in reality it is low) means reduced signal level ... and sometimes this is actually good.

So, if the device knows its antenna's gain, then why should i provide it as well?

I guess you no longer need to.

What needs to be clarified, is what happens when you set something there using frequency-mode=regulatory-domain.

E.g. if built-in antennae have 2dBi gain, then it's not possible to set this parameter to 0 or 1 ...

But it still is!
My guess, it just ignores it, if the value is lower than minimum for selected country.

mkx am sure you can set lower antenna Gain, lest say 1dbi.. i ve tested it in a rb951ui 2hnd and recently on a 952...

So what happens when i set it to 1 dbi and i use regulatory domain while my actual antenna gain is 2 dbi? Will my total Tx power be +1 dbi more than it should be or not? Does ROS ignore the 1 dbi since it knows its antenna is 2dbi?

Just tried on my RBD52G running ROS 6.45.1 and country properly set.
When I tried to set antenna-gain=0 on 2.4GHz wireless, it complained with "failure: minimal antenna-gain for this country is 3" ... So it seems to me that ROS wants me to stay legal

I'm not sure if minimum antena gain feature was retrofitted to older models or is it only available for recent ones ...

mkx you are right... i got confused...
Tried again in a 951 and same for me, " minimal antenna gain for this country is 3 (6) "

mkx can i contact you for a post here i need some help?

Now I see this too: just needed to try more countries

Now I see this too: just needed to try more countries

Yes... it lets you set Gain to 0 for some Countries... i dont know why...

I think that’s because for some devices and some countries you can work on max tx-power without breaking any rules.

One thing remains now, does a product that is indicated in the datasheet with lets say 28 dbm Tx power include the Antenna's Gain which is for example 12 dbi or not ?

You are confusing different things.
TX-power indicates the total amount of power radiated, it will not change if you change the antenna.

You are confusing different things.
TX-power indicates the total amount of power radiated, it will not change if you change the antenna.

That is wrong...
If you set regulatory domain and you have a 6 dbi antenna Gain, if you go to current Tx power tab you will see two values... one with lets say Tx power 10dbm and one indicated as total Tx power witch will be 16 dbm (10 Tx+6 Gain)...

Besides that, EiRP which is the effective radiated power is exactly that, for the values above it would be EiRP= 10 - 0 + 6 = 16 dbm , in case there are no losses...

So the total radiated power has two factors, the Tx power of our transmitter and the Antenna's Gain...

Nope.
TX-power and Total TX-power indicate values for one chain and for all enabled chains.
The difference between them has nothing to do with antenna gain.

https://wiki.mikrotik.com/wiki/Manual:I ... d_802.11ac

So the total radiated power has two factors, the Tx power of our transmitter and the Antenna's Gain...

That is totally wrong.
TX-power is a characteristic of the radio emitter, totally independent from the used antenna.
Antenna gain shows the distribution of this power in space (compared with an isotropic antenna, which radiates equally in all directions).
EIRP is a characteristic of a point in space - it shows TX-power needed on a theoretical device with isotropic antenna to have the same signal strength, that is actually measured.

xvo, if i have a 802.11 n card with lets say both chains enabled, if my Tx power is 10 dbm and the antenna Gain is 3 dbi then the total Txpower will be 13 dbm...

Without changing anything with the chains,still using 2 chains, if i set the Gain to 6 dbi then the total Txpower will be 16 dbm...

The wiki talks about changing the number of the chains 1, then 2 then 3 and how Tx power is affected by that

Again, the EiRP shows the power radiated, and that is the power that should be inside the legal limits, and TX + Gain give us the final dbm value... i dont understand why you say that Gain has nothing to do when thetr is a formula for that thing...

Have you tried it?
If you have tx-power-mode=default, antenna-gain=3dbi and tx-power/total-tx-power=14/17dbm and then change to antenna-gain=6dbi you will end up with 11/14dbm!
Because the device lowered the Tx-power to stay inside the regulations.

Seriously, just try it.
You can use tx-power-mode=all-rates-fixed, and see that setting antenna gain has no impact on total tx power.

Again, the EiRP shows the power radiated, and that is the power that should be inside the legal limits, and TX + Gain give us the final dbm value... i dont understand why you say that Gain has nothing to do when thetr is a formula for that thing...

Yes!
Tx-power + gain will give you the maximum theoretical signal that you can achieve!
So to be inside the regulations it has to be lower than specified EIRP!
But gain don't change tx-power, you (or your device) need to do it.

But gain don't change tx-power, you (or your device) need to do it.

No it wont change the Txpower, however it affects it in other ways...

For, example the Txpower will get lower and lower as we increase the Gain in order to stay legal...

And also if lets say i use an Antenna with a Gain of 6 dbi instead of one with 3 dbi, its like"doubling" the power because of the better directivity, concentration and distribution of the radiated power...

No it wont change the Txpower, however it affects it in other ways...

For, example the Txpower will get lower and lower as we increase the Gain in order to stay legal...

And also if lets say i use an Antenna with a Gain of 6 dbi instead of one with 3 dbi, its like"doubling" the power because of the better directivity, concentration and distribution of the radiated power...

All of that is true, but I never said the opposite.
And it is not what we were arguing about.

I only pointed that you have a misunderstanding of the physics of the process.
Tx-power can't include antenna gain, because they are two different things.
And indeed it is not included.

One thing remains now, does a product that is indicated in the datasheet with lets say 28 dbm Tx power include the Antenna's Gain which is for example 12 dbi or not ?

And I also corrected you about the meaning of tx-power and total tx-power columns, and that the difference between them has nothing to do with antenna gain.
And indeed it hasn't.

Nope.
TX-power and Total TX-power indicate values for one chain and for all enabled chains.
The difference between them has nothing to do with antenna gain.

You can test all the above:
1) leave only one chain.
2) set any european country and your minimal gain of 3.
3) you get 17dbm per chain and 17dbm total: 17+3 will be exactly the allowed 20dbm
4) enable the 2nd chain and you will get 14dbm per chain and 17dbm total - again

I just thought that the Total Tx power in ROS had the meaning of EiRP, thats why i wondered if the gain is included...

leave only one chain.
2) set any european country and your minimal gain of 3.
3) you get 17dbm per chain and 17dbm total: 17+3 will be exactly the allowed 20dbm
4) enable the 2nd chain and you will get 14dbm per chain and 17dbm total - again

Looks correct...

So I guess all the questions are of the table now

The main thing we figured out: Mikrotik in regulatory-domain mode won't let us break the law after all...
...For that we have manual-tx-power and superchannel!

In RouterOS 6.47.10 (May/31/2021) I had to set Frequency Mode to regulatory-domain first (and press Apply button). Then switch Installation to any [or indoor] (and press Apply button) to be able to connect to the indoor 5 GHz network.
I checked the status of the wireless interface (connection/disconnection/error state) by enabling debugging output in the Log window: I'm unable to set Country still to anything than no_country_set (the error message is: Minimal antenna gain for this country is 16 (6) and I don't know what to set in Tx power mode.

ON WinBox Push the "Reset Configuration" button when open wireless interface, then select your country,
then do not touch anything to do with "power", then configure the rest, on this way you do not rmp i cglion to the neighbors.