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EFWilson
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Noise Floor < -100 dBm, normal??

Sat Sep 29, 2012 12:47 am

Hi All

I have installed a new AP in my area and am having poor signal to my other AP using WDS. I have done some digging and it my noise floor value on the card is sitting at -113dBm. People have mentioned to me this is usually caused by a wireless card or antenna fault, is this so? When I do a scan of the area, all the frequencies show a noise floor above < -100dBm.

Thanks
Last edited by EFWilson on Sun Sep 30, 2012 8:43 am, edited 1 time in total.
 
plisken
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Re: Noise Floor > 100 dBm, normal??

Sat Sep 29, 2012 7:17 pm

with what routerboarden and wireless cards do you work?
 
EFWilson
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Re: Noise Floor > 100 dBm, normal??

Sat Sep 29, 2012 7:51 pm

with what routerboarden and wireless cards do you work?
Hi

RouterBoard Groove 2A with 2.4GHz 12dBi Vertical Omni Antenna.

Thanks
 
plisken
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Re: Noise Floor > 100 dBm, normal??

Sat Sep 29, 2012 8:25 pm

I also have a groove 2 but the results with a 10dB omni are clearly better.
Are the regional settings set correctly? and the bandweith
Is possible the antenna not of good quality or there are too many disturbance factors outside.
Maby try another antenna
Sorry for my bad englisch
 
EFWilson
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Re: Noise Floor > 100 dBm, normal??

Sun Sep 30, 2012 12:10 am

I also have a groove 2 but the results with a 10dB omni are clearly better.
Are the regional settings set correctly? and the bandweith
Is possible the antenna not of good quality or there are too many disturbance factors outside.
Maby try another antenna
Sorry for my bad englisch
Thanks for your assistance thus far, please see my response below:

Regional settings are correct.
Bandwidth is limited to 36Mbps.
I have tried my 9dB antenna and am getting the same Noise Floor value.

This is the value that concerns me, is it possible to have a noise floor so low? My Total Tx CCQ is also all over the place. What is your Noise Floor value sitting at?
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ditonet
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Re: Noise Floor > 100 dBm, normal??

Sun Sep 30, 2012 3:32 am

The lower the 'noise floor', the better.
Your 'noise floor' is not higher than 100 dBm, but lower than -100 dBm.
Notice a minus sign in 'noise floor' value.

HTH,
Grzegorz | MTCNA, MTCRE, MTCSE | konsultacje MikroTik Warszawa
It is a book about a Spanish guy called Manual. You should read it. - Dilbert
 
EFWilson
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Re: Noise Floor > 100 dBm, normal??

Sun Sep 30, 2012 8:48 am

The lower the 'noise floor', the better.
Your 'noise floor' is not higher than 100 dBm, but lower than -100 dBm.
Notice a minus sign in 'noise floor' value.

HTH,
Post corrected thanks. What I was told and am wanting to confirm is if a noise floor value is between -100dBm and -127dBm there is a problem with the wireless card or antenna and if it is between -80dBm and -99dBm that's normal -99dBm being the best?

I am relatively new to wireless so please do forgive me if I am asking a silly question but would just like some clarity on this?
 
plisken
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 10:13 am

Sorry but a had misunderstood, this is very good result.
Nothing for worry about it.
 
ditonet
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 1:06 pm

'Noise floor' value shows measured enviromental RF noise.
As I wrote earlier, lower is better, below -100 dBm is pretty good.
You should observe 'Signal to Noise' parameter in 'Wireless/Registration' tab,
it shows how much your signal is stronger than noise, 50-60 dB is OK.

HTH,
Grzegorz | MTCNA, MTCRE, MTCSE | konsultacje MikroTik Warszawa
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 4:18 pm

...this is very good result. Nothing for worry about it.
The OP is concerned that an "unnaturally" low noise floor might indicate a defective receiver. And he has a point. Even with low-power cards with no antenna connected, internal RF is usually enough to keep the noise floor above -100.
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uldis
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 6:21 pm

Sorry but a had misunderstood, this is very good result.
Nothing for worry about it.
Correct, you don't need to worry about it - it is a good result.
Older legacy chipsets could have noise level approx up to -97, but new N chipset cards has better results and could go to above -100.
 
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 6:45 pm

Older legacy chipsets could have noise level approx up to -97, but new N chipset cards has better results and could go to above -100.
I'm sure they have improved, but -113? That would be one heck of a quiet neighborhood--less than 3% as much ambient RF as I have ever seen.

You could add a second identical radio to the RB (or to a different RB in the same location) and see if they give similar noise floor readings. That would settle your concerns once and for all.
Principal, Engineering
Cape Ann Communications, Inc.
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EFWilson
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 11:28 pm

Sorry but a had misunderstood, this is very good result.
Nothing for worry about it.
Correct, you don't need to worry about it - it is a good result.
Older legacy chipsets could have noise level approx up to -97, but new N chipset cards has better results and could go to above -100.
So even if I force the Groove unit to run use b/g the noise floor could be lower than -100 and still be considered normal?

On an older RB433 that only supports b/g I'm getting a noise floor value of -93, even when I move the Groove unit to close proximity of that unit it's still reporting a noise floor value < -100.
 
plisken
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Re: Noise Floor < -100 dBm, normal??

Sun Sep 30, 2012 11:45 pm

how force je the groove for b/g setting?
 
uldis
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Re: Noise Floor < -100 dBm, normal??

Mon Oct 01, 2012 11:45 am

if you do not like such high noise floor readings then for the N chipset cards you can manually set the noise floor by using noise-floor-threshold setting.
 
lorenzesz
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Re: Noise Floor < -100 dBm, normal??

Wed Jul 10, 2013 11:31 pm

I have -113 dBm with rb912 here
 
stefanosp
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Re: Noise Floor < -100 dBm, normal??

Tue Jul 16, 2013 5:53 pm

I Have -118dB on RB711
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Ivoshiee
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Re: Noise Floor < -100 dBm, normal??

Tue Jul 16, 2013 11:27 pm

Noise floor should not be an issue itself. When you see strange issues with RF signals then start to tinker with it.

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