How to read signal strength of Airport Base Station

Not with v6.x of the AirPort Utility for OS X or macOS. You could with the iOS version of this utility or via the Wi-Fi icon in OS X/macOS. Otherwise, a number of third-party apps can do this for you.

For the iOS AirPort Utility:

• Method #1:
  • Tap on the AirPort Utility app.
  • Tap on the AirPort base station.
  • Tap on Wireless Clients.
  • Tap on any of the clients that are connected to the AirPort.
  • Tap on Connection.
  • RSSI = signal strength (Granted, this would be the signal strength as "seen" by the iOS client where it is located in respect to the base station. However, one of those clients could also be another base station.)
• Method #2:
  • Tap on Settings.
  • Tap on AirPort Utility.
  • Enable Wi-Fi Scanner.
  • Exit the Settings app.
  • Tap on the AirPort Utility app.
  • In the upper right corner you should now have the Wi-Fi Scan option. Tap on it.
  • Tap on Scan.
  • You should now get a continuous real-time scan of your Wi-Fi network. Again, this is what the iOS client "sees" as your network.

For macOS:

• Method #1:
  • Option-click on the Wi-Fi icon on the macOS menu bar.
  • In addition to the RSSI value, you should see a number of other Wi-Fi related ones. Again, this would be how your Mac clients "see" your Wi-Fi network.
• Method #2:
  • Run Wireless Diagnostics.
  • From the Diagnostics menu bar, choose Window > Monitor. Alternatively, you could also choose either Performance or Scan.

Third-party solutions:

• WiFi Explorer
• WiFi Scanner
• iStumbler

The v6 airport utility has great limitations.. It is much closer to toy hammer rather than real tool.

But you can see at least half the connection.

Click on the wireless link airport icon in the airport utility.. and float your mouse pointer over the connection. It takes a second or so for it to respond.

Much the same as the instructions Tesserax gave you for iOS version really.. (he may have missed it in the Mac version.. I found it by accident).

When you look the summary list in the background it shows the connection as Unknown.. it has been Unknown since about Yosemite.. but the extra info is hidden in behind it.. The link then shows up with actual speed and RSSI.

I spent a lot of time getting this to work on 5ghz to get the speed up.

What is a total failure is the other side.. aegen5 does not even show as a wireless client of aegenx.

Running the older version of airport utility on this Mac (possible up to Sierra where it got broken).

I can see the values on the other side of the wireless bridge match very well.

I believe that the only way you can "see" a base station as a wireless client is if it is extending another base station. In that case, it should show up as a client in the AirPort Utility ... and the methods I provided should work.