This is an app for amateur radio operators with a narrow band of audio frequency, spectrum scope & waterfall display.

You can get a rich display by microphone inputting the speaker output of a radio that does not have a spectrum scope or waterfall function. The FFT allows you to distinguish between the dot and dash of Morse code.

[function]
1. Ability to change the speed of the waterfall
2. Ability to adjust the level of audio input
3. Function to switch the display band between wide and narrow
4. Display pause function (pause / cancel by touching the screen)
5. Function to switch the cross hatch ON / OFF by longTap
6. Frequency resolution is fixed at 40Hz.
7. Function to switch the USB/LSB by Left/Right Swipe
8.Recording/Playback function of Input Sound

RST Scope(Free)
https://www.youtube.com/watch?v=1s9RvOFp52g