Why does the Target Power not equal the Transmit Power?

Jamieinbox
Getting noticed

Why does the Target Power not equal the Transmit Power?

Why should there be any difference here when hard coding (turning off auto power).

Thanks in advance, Jamie

5 REPLIES 5
ww
Kind of a big deal
Kind of a big deal

There are regulatory limitations that limit the dbm  on some (or all) channels. It depends where you live and it can vary  between channels and type of ap(antenna-dbi, beamforming). 

The dashboard allows you to set the max, but it will not alway use it.

 

If you press  the I (info button) on the dashboard page it will give you some additional  info and a link to documentation

Inderdeep
Kind of a big deal

@Jamieinbox : what transmit power you are getting 12? YOu can set manually i think to 16 

Regards/Inder
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Jamieinbox
Getting noticed

Thank you both for responses. I wanted to see how far the signal would go with open hallway and with a first set of offices with drywall  measuring at 5Ghz from 29, 25, 20, 15, 10, 5 & 1. Please see PDF for details. I'm not sure I understand the power chosen vs. output, but I saw something about having to wait to see the adjustment, as well. I changed the power, took note of the change, and walked. 7_2.png7.png6_2.png6.png5_5.png5.png4_2.png4.png3_2.png3.png2_2.png2.png1_2.png1.png

ww
Kind of a big deal
Kind of a big deal

GiacomoS
Meraki Employee

Hey Jamie,

 

Echoing what super knowledgeable ww mentioned, this is likely to do with the regulatory domain.

Each country has a specific maximum power that it allows on its soil, for example for Europe you are likely looking at 20/23dBm (depending if you are on 2.4 or 5 GHz)  maximum ( source ). 

 

If we assume we have a brand new MR46 broadcasting on channel 136 (5GHz), we can look at the datasheet  , see that the antenna gain for the 5GHz radio is at 6dBi, factor in 3 dB for beamforming and we can then reverse the EIRP formula:

 

Maximum transmit power = 23 dBm (maximum EIRP) - 6 dBi (antenna gain) - 3 dB (beamforming) + 0 dB (pretending for a second we don't live in the real world where there is cable loss) 

 

Which results in 14 dBm of maximum transmit power achievable in Europe on the 5GHz range. 

 

Dashboard would still allow you to target the highest transmit power possible (30), but it will then do all the calculations and work its magic for you to ensure you remain compliant to the legal regulations for wireless transmission. 

 

Hope this helps!

Giac

 

 

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