Max radio transmit power on MR57 - limited to 23dBm?

[Russell_F]

Recently started experiencing an issue with the radio transmit power on our MR57s.  For our environment, and based on our experience with prior Meraki APs (MR34s, MR52s), we saw anything from 26-30dBm transmit powers (as shown on Wireless -> Configure -> Radio Settings in the dashboard) on both 2.4Ghz and 5Ghz radios.

At some point in the last few months, we've seen the transmit powers drop significantly. Now everything maxes out at 23dBm across all radios.  I believe (but can't be 100% sure) that this started sometime after we upgraded the APs to MR57s.  At the same time, users started complaining about reduced WiFi coverage at the edges of our network, so pretty sure something is up.

By way of troubleshooting:

• The APs are not operating in low power mode, as confirmed in the dashboard.
• The Target power in the assigned RF Profile is set to 30dBm, and no radio has any manual override.
• The MRs are running only GA code - currently MR 30.7.1.
• We are not using any DFS channels.
• We only have 3 APs so there's no overlapping bands between the APs.
• We are not in a crowded RF space, with between 4-7% average channel utilization on the 5Ghz band as an example (and around 20% on the 2.4Ghz band).
• The MR57 flex radio is set to a second 5Ghz radio (although have tried disabling it to see if it helps).

I raised a ticket with Meraki support, and after much back and forth over a period of a month, they've come back to me having "consulted with engineering" and are saying that because of the antenna gain in the MR57, the max transmit power that will *ever* be shown in Radio Settings in the dashboard is 23dBm, and therefore everything is working as it should.

This doesn't seem right to me (for all the reasons mentioned above) but, before I push back on support, I wanted to see if anyone else in the community could check their own dashboard and see whether they have any MR57s that are showing a higher Transmit Power than the 23 I mentioned before.  Hopefully it's someone in the same regulatory domain (I'm US based, so FCC).  If I can't find anyone else with something higher, I'll have to grudgingly accept their conclusions.

Thanks!

[Russell_F]

To add, I've reviewed the information at https://documentation.meraki.com/MR/Radio_Settings/RF_Profiles#Max_Radio_Power_Limitations, and I don't believe any of it would explain this situation...  but open to feedback. 

• Regulatory Domain - I’m in FCC/US so I understand this isn’t a problem?
• Channel Selection/Band Edge - this is happening across all radios regardless of band, so not relevant to my situation.
• Bit Rate - minimum bit rate on 2.4Ghz is 12, and on 5Ghz it’s set to 9.  Which I understand is relatively low.
• AP Model - can’t find the RF performance table for the MR57, so if anyone can point me in the right direction, I’d appreciate it.

[RWelch]

Curious to hear if you are assigning separate RF Profiles to each AP?  Or one RF Profile to all 3 APs?

Not assuming this to be the culprit but I've had mixed results similar to what you described.

[Russell_F]

Same single RF profile is being applied to all AP radios.  I've set the target transmit power to 30dBm now, but at the beginning of all this is was for years set to 26-30.  However, it never goes above 23dBm....

[ww]

I think its normal,it get 17 on lower and 23 on higher channels here in EU.  it has to do with antenna gain and beamforming that you have to add up.  Look at te last post here

https://community.meraki.com/t5/Wireless/Why-does-the-Target-Power-not-equal-the-Transmit-Power/m-p/...

Documentation

https://documentation.meraki.com/MR/Radio_Settings/EU_Compliance_Information

[GreenMan]

The rules are certainly different between Europe and the US (FCC, where Russell_F is operating) - and more restrictive in Europe (where I am too @ww )

From a quick look at the FCC rules, I think 30 dBm may be legal, but I seriously question whether you'd ever want to actively use it;  clients will not be generating that kind of output, so you'd likely end up with one-way transmission, if you're reliant on that kind of power setting.

[PhilipDAth]

I am going to take a different tack to the others (they have addressed it well already).

How closely have you looked at the clients?  Is it all clients with the issue, or only Windows machines.  Is it all Windows machines, or only machines with a WiFi chipset by a particular manufacturer?

Have you tried taking a problem device, and upgradig the WiFi drivers on it?  Don't use the OEM manufcaturers drive (such as Lenovo, Dell, HP, etc) - but get the actual drive from the WiFi chipset manufcaturer (such as intel).

This would have just as easily been a Windows/Device update.

Is it happening across all APs, or perhaps only a single AP?  Has there been any other newly added devices in the WiFi environment?  Cordless phones.  WiFi LEDs (saw a site recently where these flooded the WiFi network taking it down).

Do the clients report a good signal strength?

What does Wireless Health and Wireless Overview say?

Under Wireless Overview, do these show anything interesting (particularly with a known problematic client)?

I just re-read your post - you don't actually mention there being an actual issue that clients are experiencing.  You are simply noticed a different power level.  Are clients actually reporting issues?  If so, refer above.