IMPORTANT: Due to changes in Android OS is Android PIE 9 support limited. OS limits app up to 4 scans per 2 minutes. Future Android Q 10 will probably remove any support for wifi scan for apps. Proof bellow. This app is tested and provided primary for Android 8.1 and lower. If you have higher version or upgrading to higher version its up to you.

https://developer.android.com/reference/android/net/wifi/WifiManager.html#startScan()
"This method was deprecated in API level 28. The ability for apps to trigger scan requests will be removed in a future release. "
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Wifi Analyzer will provide useful information about wireless signals around you. App supports 2.4Ghz and 5Ghz.

- NO ADS
- screenshot/CSV export of found networks

- Helps to find optimal placement for wifi receivers
- Provides you information individually on wifi channels
- Shows signal strength in history graph
- Recommends the best channel for new AP
- Information of the channel width (20/40/80MHz - only Android 6+)

Note: Android 6+ (Marshmallow) requires LOCATION permission and location enabled - the reasons explained on the official website android.com: http://developer.android.com/about/versions/marshmallow/android-6.0-changes.html#behavior-hardware-id

Wifi Analyzer Pro will give you useful information about wifi signal around you.