I have previously done some testing on the Meraki APs regarding max transmit power an different external antennas, versus the maximum allowed EIRP in my regulatory domain (Denmark / ETSI) because the external ones , especially the MR46E had a clear problem when compared to a normal Cisco AP. I never got around to testing on 5Ghz. 😕 Sorry. But my results are here : https://docs.google.com/spreadsheets/d/1-s5IOMg09DTCFnODNapsYXta_onfO4W6SqG3E6sn9tg/edit?usp=sharing I your case, the antenna gain on 5Ghz in a MR57 is 5,5dbi, and the max EIRP in the US (as far as I remember) on UNII-1 is 23dbm (200 mWatt), on the UNII-3 channels in the US its 30dbm (1 Watt) ?? So the offset, if the AP is running in UNII-3, and you have your 23dbm radio power + 5,5dbi antenna gain = 28,5dbm EIRP , is missing 1,5 dbm of transmit power. Perhaps that AP is not able to turn up / down the power in such small db steps (this is me speculating, I have no knowledge of this). But it could mean that this is the max power of that AP.
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