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Fumi
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Wrong TX-power values.

Tue May 04, 2010 11:48 am

There are several radios that RouterOS does not read well the TX-power value. RouterOS does not know the offset of all radios on the market.
If I have 25dBm radio but routerOS read max power 17dBm. The offset is 8dBm.

The question is.. I set TX-power mode=manual and if I configure for rate 6Mbps=25dBM, this configuration is good? or I have to configure 6Mbps=17dBm beacuse radio's offset...

Thanks!
 
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normis
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Re: Wrong TX-power values.

Wed May 05, 2010 9:05 am

leave tx power at default and it will run at the max, don't change the value. probably the card has some power amplifier built it, which is unknown to software.
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aaa
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Re: Wrong TX-power values.

Wed May 05, 2010 9:52 am

Better way to get max. TX power stick power meter to wireless card and increase TX-power until you reach tx-power noted on card documentation for each datarate. Else I noted that default TX power for UBNT wireless card is very far from max. TX power listed in UBNT documentation.
 
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normis
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Re: Wrong TX-power values.

Wed May 05, 2010 10:09 am

1. tx-power max depends on datarate and chosen frequency, the advertised maximum is never true in all datarates and frequencies
2. never trust chinese advertisements, chinese brands mostly show false maximum in their advertisement
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Fumi
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Re: Wrong TX-power values.

Wed May 05, 2010 11:03 am

Thanks for replies!

SR71-15 is 27dBm radio. In routerOS 5beta2 realTX Power=19dBm and TotalTXPowe=22dBm (6Mbps rate).
I know the best way is leave default settings but If I need to configrue to manual settings what is the good value for rate=6Mbps?Can I set to 27dBm to 6Mbps datarate?

Thanks!
 
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Re: Wrong TX-power values.

Wed May 05, 2010 11:47 am

you need to consult with UBNT about their power offset. Looks like it is 10db (but I am not sure), so to get the 27 tx-power you need to set the tx-power to 17. Total power is higher by 3db, as it is N card and most likely 2 chains are enabled.
 
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Re: Wrong TX-power values.

Wed May 05, 2010 6:23 pm

there is a sr71 tx power thread in the forums i started earlier. search. the offset is 7db I believe, so routeros is not using full power with defaults. you have to be careful though and set each data rate, i dont think card-rates will make best decisions. i havent had time to come back to this but i am very interested in it and will shortly.
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colebert
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Re: Wrong TX-power values.

Wed May 05, 2010 8:34 pm

Winbox does not give you the ability to set your MCS rate powers. To fully fix the issue you will need to set the card to manual power and then go into the command line and manually edit that way.
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wispwest
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Re: Wrong TX-power values.

Thu May 06, 2010 6:17 am

^^ wow this still isn't fixed in 5.0beta? hrm... I suppose Mikrotik sets the correct power for their R5Hn card though right?
 
changeip
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Re: Wrong TX-power values.

Thu May 06, 2010 6:58 am

i dont think they consider it a bug ... unless there are cards burning up from it they probably wont care. its just not using the fullest amount of power available by default i think. i will make some tests this week and report back.
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colebert
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Re: Wrong TX-power values.

Thu May 06, 2010 8:37 am

^^ wow this still isn't fixed in 5.0beta? hrm... I suppose Mikrotik sets the correct power for their R5Hn card though right?
Precisely. :?
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hurley12345
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Re: Wrong TX-power values.

Thu Oct 28, 2010 11:23 am

^^ wow this still isn't fixed in 5.0beta? hrm... I suppose Mikrotik sets the correct power for their R5Hn card though right?
Precisely. :?
Any ideas as to why Miktotik still haven't fixed the Tx power issue with the SR-71 card.
 
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Re: Wrong TX-power values.

Thu Oct 28, 2010 3:49 pm

So you all have contacted Ubiquiti and asked why they haven't fixed their bug on the tx-power? If they didn't use an offset (let me guess here. A 10db linear amp on the standard chipset output?), there wouldn't be a problem.

What did Ubiquiti say about this?

Just my opinion...
 
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colebert
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Re: Wrong TX-power values.

Thu Oct 28, 2010 4:52 pm

Their bug? Is it their bug that drops the TX power 10dB when you upgrade from ROS 4.11 to ROS 5.0rc2?
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SurferTim
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Re: Wrong TX-power values.

Thu Oct 28, 2010 4:54 pm

Their bug? Is it their bug that drops the TX power 10dB when you upgrade from ROS 4.11 to ROS 5.0rc2?
Yes, that is EXACTLY what I am saying! :D

ADD: That was a bit short. I suspect the reason there is a difference is: They forgot to correct for Ubiquiti's "10db offset" bug. So for that you will put the blame directly on MikroTik?

If you want to use a specific company's product, know how to use it. Ubiquiti is known for that offset. I have a SR2 here. Can't even get one now, can you? And this is not the first router product that I have compensated for the now infamous Ubiquiti "10db offset".
 
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colebert
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Re: Wrong TX-power values.

Thu Oct 28, 2010 7:40 pm

Mikrotik releases a new version of their software that results in the card performing 10dB worse than their previous version it's somehow UBNT's fault?

Seems to me that if care would be taken to make sure ROS can make proper use of a well-known and respected brand and model of 802.11n cards that this would not be an issue. I can't help but wonder what part having their own line of wireless cards plays into this. Latvian anti-trust law tradition must still be a work in progress. :)
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SurferTim
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Re: Wrong TX-power values.

Thu Oct 28, 2010 8:52 pm

Hi colebert. I am not trying to imply that MikroTik is not part of the challenge. If they compensated for UBNT incompatible settings in the past, then they should continue to support that.

And I thought 17 was the default value for tx-power, not the reported power setting of the card. Every card I have used in RouterOS units starts with tx-power=17 when I changed tx-power-mode the first time, even the R52 and R52H. If that is not correct, please let me know. On this I could be wrong. I will start paying closer attention now.
 
changeip
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Re: Wrong TX-power values.

Thu Oct 28, 2010 11:40 pm

Mike at ubnt told me the offset for the SR cards is 7db. The offset cant change between versions on the card itself, so its either mikrotik that is now compensating for it, or its a bug. If you purposely increase the tx power can you get it back up to where it was (depending on if you feel like burning up your card on accident)

http://forum.mikrotik.com/viewtopic.php ... db#p203551
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Re: Wrong TX-power values.

Fri Oct 29, 2010 2:02 pm

Thanks, changeip. But that is not correct. The SR71 may have 7db offset error, but the older SR2 has a 10db offset error.

And Mike at UBNT apparently told you the same thing they told me years ago, changing only the amount of the error: "We have a 7db output power error. We know about it, and we're not fixing it. Deal with it."

Does any other company have an error like that? Or it could be that anti-trust thing mentioned earlier. Imagine if you set a SR71 at tx-power=17 and a R52H tx-power=17. Boy! Would that SR71 look good!
 
changeip
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Re: Wrong TX-power values.

Fri Oct 29, 2010 7:28 pm

I meant SR71 cards, not SRx cards... Sorry. I know there is a 10db offset on the legacy cards.

The offset is put there to get around madwifi limitations (I think), not because one company wants to trick another. Wasn't there some max limit in driver land that had to be overcome, so building an offset into the card could allow the driver to push the card to its real max? It's in the firmware for a reason on the higher powered cards.
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