Tx Power regulations

Hello, I know this is an old thread, if the best course for me is to start a new one feel free to tell me and I will do so, but I have been having lots of problems in regards to transmit power in my openwrt routers, and would like some help and clarification.

I live in brazil, where the maximum allowed power is 30dbm for 2.4 ghz, but it seems that openwrt sets my limits arbitraraly, if I have it stock, on driver default, my US bought router (TL-WR842ND, as mentioned here) outputs 21dbm, but if I change to brazil it limits me to 17dbm, and yes, I need the extra power, I use it in a rural setting, and do not care if my link is assymetrical, because download (that being, the router transmitting something to me) is my priority, does anyone know whats up with that? and why doesn`t openwrt hand control of those things to the user? it goes against the premiss of open-source software based on my understanding.

also had that problem today with this router I just bought.

This forces me to use my router as if I were on the US, with certain channels locked (that are available here) and is really sad for me to see something so good that is openwrt doing things like these, and hurting what I would describe as the perfect os for any router.

So if your concern is Rx what issue are you having?

Also, did your stock firmware count the antenna gain?

I think you didn't understand, one thing has nothing to do with the other, and when I say rx, I explained that it was my devices rx (thus the routers tx), and it was only for context

As for antenna gain, once again, it may or may not count, AFAIK I have no way of knowing, the issue is with regulatory domains, brazil's maximum allowed power on 2.4 GHZ is 30dbm, and openwrt is limiting me to 17dbm, and obviously I don`t have an antenna gain of 13dbm, therefore pointing the source of the problem to openwrt regulatory domains, as far as I understand it.

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I don't own the device so can't give specific answer, but I think it could help whoever can help if you mention what version of OpenWrt you are using.

It's probably also worth mentioning if there is any indication of region next to the model number at the bottom of the device.

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I'am running 19.07.4 stock.

As for the bottom of the device, I have some pictures, and it is of chinese origin (sold as an openwrt device), but what does that change? shouldn't it work acording to the regulation setting? isn't this why there is such a setting in place?

Sometimes manufacturers make different specs for different regions, which in turn might require different OpenWrt builds, so it helps with the h into is complete.

By thy way, its a good privacy and security practice to redact MAC and public IP addresses when you post info online.

Well, as for the mac, I`am already discussing what device I have, so I do not see why this would make a difference, I have no security measures in place that rely on the MAC address of the device (can be easily spoofed) and those are the stock IPs and passwords, not the ones I configured :wink:

also: seller advertises 20dbm on this router, so I don`t think the problem is a regional lock, because if you refer to my original comment, I had this problem with another router as well, and older tplink one, that when running as if it wore in the US (where it was bought) it would go to a higher maxumim power than brazil, and here we have the same maximum output power limitations per legislation.

Clearly the firmware and sticker are "value added" features by the seller, before selling they've replaced the OEM Chinese firmware for you. Did they get it direct from downloads.openwrt.org, or is it their third party build?

The dBm numbers you may see during configuration don't mean an awful lot. For example sometimes antenna gain is factored in and sometimes it is not. The only real way to compare radio output of two routers and say one is more is an on-air range test.

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Well, they claim it is stock directly from http://downloads.openwrt.org/, in any case, I did reflash it with trusted stock, and nothing really changed, as for the on-air test, my crappy router with internal (also crappy) antennas goes a tad bit farther than this one, so that's that, and as for antenna gain, I stated in my second comment that even factoring that in (or out, in this case) it doesen't make any sense for these to be the values.

Please find the Brazilian regulation...this has been on my mind since you mentioned it.

I usually do not try to do calculations; because people don't agree with actual radio terminology anyways...you're already convinced they're identical. You can likely find 1-2 threads where this was attempted to be explained...I recall one where some versions recalculated the antenna and people were pissed, lol. :laughing: ...til on-air tests.

But since I really don't want to search government sites trying to read Portuguese - if you're willing, I'll take a look.

Also, you never made an original post, you revived 2 year old thread.

Lastly, setting to a nation that's not yours is illegal (at least in the US it is). This really makes me think the Brazilian regulation is not the same.

well, firstly, I mean comment, not post, I will correct my mistake, English is not my first language, and I asked if it was better to start a new thread, and no one objected to my comment reviving this one, so that's what I did.

I assume by your comment that you think I'm American, I have to say I'm flattered, because I consider my English bad, given that I live in brazil, and never lived abroad.

any ways, for those interested in helping me, and many other with this problem, I found this link, old by now, but I'm lost as to where to open a ticket for this problem, on this hardware, because I found mentions of this scattered across many repositories, the forum, and the openwrt.org git

also, when running cat /sys/kernel/debug/ieee80211/phy0/mt76/rate_txpower
I get
CCK: 0 0 0 0
OFDM: 0 0 0 0 0 0 0 0
STBC: 0 0 0 0 0 0 0 0 0 0
HT: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
VHT: 0 0 0 0 0 0 0 0 0 0

leading me to believe the problem is with the driver or factory partition, as stated in this other post

I hope we can all have a civil discussion, and grow the community by helping each other, as well as having the best out of our hardware, opensource.

As for regulations, I found 5, all revoked, because our government is a mess. I will continue to search, last time I did so, I found out it was 30dbm. meaningless affirmation on my part without sources, I know, as such, I will go after them again, and once found I will update this comment to contain them.

this seems to be correct

source: http://www.ppgia.pucpr.br/~jamhour/Pessoal/Atual/WLAN-Parte1.pdf

as such, I will be using this router in a rural area, outside the city, where my maximum transmit power abiding regulations would be 4W

As an observation, this is somewhat clear in Resolução nº 506, de 1º de julho de 2008 da Anatel, but this one, that seems to be the basis for the table, has been revoked, and substituted by Resolução nº 680, de 27 de junho de 2017, but this new one is very hard to understand, therefor I cannot yet state that this information is 100% correct, but it seems like it is.


current wireless-regdb
country BR: DFS-FCC
	(2402 - 2482 @ 40), (20)
	(5170 - 5250 @ 80), (17), AUTO-BW
	(5250 - 5330 @ 80), (24), DFS, AUTO-BW
	(5490 - 5730 @ 160), (24), DFS
	(5735 - 5835 @ 80), (30)

...No, I think you're Brazilian. That's why I noted it's likely illegal to set your device to US.

I'm asking you to search because out of approximately 5 times someone has made such a topic, the REGDB was correct. Since it takes a lot to find the regulations - and it's the only way we can know if you're telling the truth and if your knowledge is current, we need to see them.


:+1: I'd follow this.

That ticket has been discussed, this is why I mentioned people disagree, and could you find the current regulation. You already proved by your own admission in Post No. 23 that the regulations changed.

When you hit the button, you post.

thanks for the wireless-regdb, upon finding the regulation, how do I proceed to get it changed if it turns out to really be incorect?

as for the power of my router, given the dev archive and the command output, as well as other threads, this seems to be a problem of the driver or the router partition, where should I post to get help for these?


Notify the upstream maintainer of REGDB. It is not maintained by OpenWrt. You will need offiical paperwork from Anatel - the maintainers of the REGDB handle this already.

Hummmm...just make a new post...I disagree you have a problem, though.

It is illegal for you to edit this partition - if you mean "WiFi parition" (at least in the US). It's actually "shady" to use a backup of another identical device.

yeah, using a different firmware I have more range, something reported on by other people as well, but sure, since you act as the know-it-all here, I will leave this be.

just a tip: try to work on your people skills just a bit, there was no need to act like this when all I wanted has a little help :wink:

SMH, I always know when people will get mad about REGDB.

I hope you the best for your router.

I have some ideas, but you think I'm not trying to help. e.g.:

  • Did it have a new or older REGDB???????
  • Can you test with a firmware with an old REGDB? :bulb:

Maybe they just changed the power regulations!

:wink: :brazil: :vulcan_salute:

Trying hard, but you don't seem as you you want any help...nor find/provide documents that can (before telling me about people skills).

(You won't make me feel bad because you want to parlay with the radio laws - that's another thing people seem to not understand. The documents will clearly show.)

Well, you definitely help, but the thing is, instead of working the problem you just seemed like someone showing off, instead of considering the possibilities.

well, for the land of the free it definitely seems like this is turning into a dictatorship, correct me if I'm wrong, but editing a partition cannot possibly be illegal, transmitting outside the regulations on the other hand, yeah, this is the type of misinformation that I dislike.

In any case, I will create a new post, but for future viewers sake, I will answer these

on another post, a user tried a version of openwrt before the new brazilian regulations came out, and had the same problem, all indicated that the partition is correct but the driver isn't parsing it correctely, therefor a solution was to alter the partition.

well, I provided a document from a well regarded university here, and the interpretation of the latest documentation from anatel, as well as the number of the regulation, if you search in google it is the first link that appears, but here you go

Title 47, United States Code of Federal Regulations, Part 15:

users manual or instruction manual for an intentional or unintentional radiator shall caution the user that changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate the equipment

Yes it can be illegal - it is illegal, and you are wrong. (I'm not trying to "show off" here.)

Good conclusion, see above.

Which likely has a licence, or their engineering students do.

Why is it illegal:

Because it's a radio, you have to calibrate it not edit data in files. :wink:

You are not the manufacturer of the radio - hence not the "compliant party". This is illegal in most nations - and hence not allowed discussion on this forum.