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macrumors regular
Original poster
Jun 19, 2009
I have a 5th Gen Airport Extreme running firmware version 7.7.7.

According to Airport Utility, all of the connected devices have an "Excellent" connection, with a data rate of 300 MB/s, an RSSI in the -55 to -59 range, and 802.11a/n mode. That suggests things are fine.

BUT, on a MacBook Air I have installed WiFi Signal, and that software tells me that in most of my house, I have at best a "Good" connection, and in many places a "Poor" connection with a S/N ratio of about 22. Even when the laptop is in a place where WiFi Signal reports a "Poor" connection, Airport Utility tells me that the Airport Extreme is reporting an "Excellent" connection.

Whom do I believe here? Are these two data points telling me different things? How do I assess the validity of what I see?


macrumors member
Jun 12, 2015
Well if you RSSI is -55 to -59 but your SnR is only 22... you have a lot of noise, especially for an a/n channel. 802.11a/n does extremely well in open areas but is a very poor performer when there are things in the way, especially metals. I have an 802.11 a/n access point that is only about 50 ft away from me but my computer always reverts to the 2.4 Ghz channel because there is so much physical material between the AP and my computer. I can force the 5Ghz channel and it works well but the SnR is significantly lower because of the signal side (not the noise).

Usually the built in Wi-Fi software only cares about signal, they don't care about noise. so it sees a RSSI of -55 and says "this is great" but if you something else on the same channel blaring away and gives you a noise floor around -70 that isn't very good. In your case the noise floor is around -78 to -81. You may want to make sure that you don't have any other 5Ghz items on the same channel as your wifi, it is extremely rare for 5Ghz to bleed through buildings so it is unlikely that is coming from your neighbor unless you live in an apartment or townhouse type area. even if it is there should be enough channels to choose one that is not as noisy.
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