RST Decoder
Free
3.3.0for iPhone
Age Rating
RST Decoder Screenshots
About RST Decoder
This is an App that decodes Morse code input from the microphone.
It is a Morse practice App that you can use to check if you are keying the correct code.
Signals with good S/N can be decoded correctly, but signals with bad S/N cannot be decoded correctly.
Also, the performance will be degraded for extremely slow or fast signals.
Usually about 5 to 10 characters are required for speed synchronization of Morse Code.
Adjust the input signal so that the peak value changes from level 6 to level 7.
Make fine adjustments to each parameter according to the reception status.
[Additional Functions]
-In addition to the decoder using BPF, a new decoder using FFT has been added so that it can be switched according to the usage.
-AFD (Auto Frequency Detector) function has been added to the decoder using BPF, and BPF can be set automatically by pressing the AFD button.
-The decoder using FFT automatically follows the strongest signal in the band by AFD (Auto Frequency Detector) and AGC (Auto Gain Control). You can also hold the AFD / AGC parameters by pressing the Lock button.
* There will be a time lag of about 1 to 2 seconds for AFD tracking.
[Control parameters]
1. Audio Input Level
2.BPF ON/OFF
3.BPF of Center Frequency
4.BPF of Band Width
5.CW Speed Control ON/OFF
6.CW Speed Control Low, Mid1, Mid2 or High
7.Delete All Decoded Text
8.Realtime CW Signal Display
9.Input signal recording / playback function
*Japanese/KANA text is not supported.
[Note]
Since the signal after BPF is output to the audio output, it can also be used as an AF-CW filter.
[URL of this App working example video]
https://youtu.be/Pwp7W4m-m34
It is a Morse practice App that you can use to check if you are keying the correct code.
Signals with good S/N can be decoded correctly, but signals with bad S/N cannot be decoded correctly.
Also, the performance will be degraded for extremely slow or fast signals.
Usually about 5 to 10 characters are required for speed synchronization of Morse Code.
Adjust the input signal so that the peak value changes from level 6 to level 7.
Make fine adjustments to each parameter according to the reception status.
[Additional Functions]
-In addition to the decoder using BPF, a new decoder using FFT has been added so that it can be switched according to the usage.
-AFD (Auto Frequency Detector) function has been added to the decoder using BPF, and BPF can be set automatically by pressing the AFD button.
-The decoder using FFT automatically follows the strongest signal in the band by AFD (Auto Frequency Detector) and AGC (Auto Gain Control). You can also hold the AFD / AGC parameters by pressing the Lock button.
* There will be a time lag of about 1 to 2 seconds for AFD tracking.
[Control parameters]
1. Audio Input Level
2.BPF ON/OFF
3.BPF of Center Frequency
4.BPF of Band Width
5.CW Speed Control ON/OFF
6.CW Speed Control Low, Mid1, Mid2 or High
7.Delete All Decoded Text
8.Realtime CW Signal Display
9.Input signal recording / playback function
*Japanese/KANA text is not supported.
[Note]
Since the signal after BPF is output to the audio output, it can also be used as an AF-CW filter.
[URL of this App working example video]
https://youtu.be/Pwp7W4m-m34
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What's New in the Latest Version 3.3.0
Last updated on Jan 23, 2026
Old Versions
You can call a decoder that implements the new algorithm.
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Version History
3.3.0
Jan 23, 2026
You can call a decoder that implements the new algorithm.
RST Decoder FAQ
Click here to learn how to download RST Decoder in restricted country or region.
Check the following list to see the minimum requirements of RST Decoder.
iPhone
