MacBook Wireless Diagnostics
Wi-Fi Analyzer on an Android phone is the best free tool for analyzing an diagnosing problems on Wi-Fi.
However, I use an iPhone and a MacBook. OSC comes with a powerful built-in Wi-Fi analyzer. This page shows how to access it.
OSX on the MacBook, has a utility called Wireless Diagnostics.
Open a Finder window and Scan "This Mac" for: Wireless Diagnostics
Open Wireless Diagnostics, the one with Wrench and Screwdriver app at the bottom of the screenshot below
Optional: Once open, click on options and keep this app in Dock
See the image below, ignore the pop-up window and the Continue button
Click on Window menu bae item and select Scan (or use shortcut option-command-4)
It will scan available SSIDs and display RSSI, Noise, Channel, Security and so on. See the sample below