# RST Decoder Pro — Audio Morse code Decoder

> Mobile application that decodes audio Morse code input from the microphone. (iPhone/iPad app by koji kamogawa.)

- Source: https://appshunter.io/ios/app/rst-decoder-pro/id1521025545 (this page in markdown: same URL + `.md`)
- Developer: [koji kamogawa](https://appshunter.io/developer/1488210713)
- Category: Education, Utilities
- Price: $1.99
- Rating: 5.00/5 from 1 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 17.0 · 1 MB
- Languages: American English, Japanese
- Released: 2020-06-30
- Data updated: 2026-08-03
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/rst-decoder-pro/id1521025545/reviews.md

## What is RST Decoder Pro?

This is an App that decodes Morse code input from the microphone.

I recommend that you try the basic functions and usage with the free version before purchasing.

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.
* The Pro version also supports waterfall display.

[Control parameters]
1.Language select English and Japanese(KANA)
2.Audio Input Level
3.BPF ON/OFF
4.BPF of Center Frequency
5.BPF of Band Width
6.BPF of Shape
7.Notch ON/OFF
8.Notch of Center Frequency
9.CW Speed Control ON/OFF
10.CW Speed Control Low, Mid1, Mid2 or High
11.Delete All Decoded Text
12.Realtime CW Signal Display
13.Input signal recording function.
14.Playback function from the file list.
15.Support the Garbage Data reduction function

[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(Free version)  working example video]
The GUI is slightly different, but the basic functionality is the same.
https://youtu.be/Pwp7W4m-m34

## Key features

- Microphone Morse code decoding
- BPF and FFT decoding methods
- Auto Frequency Detector (AFD)
- Auto Gain Control (AGC)
- Real-time CW signal display
- Waterfall display (Pro version)
- Adjustable control parameters

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/rst-decoder-pro/id1521025545/reviews.md

### 1/5 — No good

*2020-09-13*

As a Licensed HAM operator I have to say this is no good for decoding Morse much less anything!!!!!!

**Developer response:** I am very sorry for your bitter evaluation. I understand and explain when this decoder doesn't always work, and I also provide a free version of the software to check. However, I would like to continue studying software improvements, even if little by little.

## Frequently asked questions about RST Decoder Pro

### What is RST Decoder Pro?

RST Decoder Pro is a mobile application designed to decode Morse code signals received through your device's microphone. It offers advanced features for accurate reception and practice.

### How does RST Decoder Pro decode Morse code?

It utilizes two primary decoding methods: a Band Pass Filter (BPF) decoder and a Fast Fourier Transform (FFT) decoder. You can switch between them based on your needs and reception conditions.

### Does RST Decoder Pro have automatic adjustments?

Yes, it features an Auto Frequency Detector (AFD) and Auto Gain Control (AGC) to automatically adjust to the strongest signal and optimize reception. The AFD may have a 1-2 second lag for tracking.

### What control parameters can be adjusted in RST Decoder Pro?

You can adjust language selection (English/Japanese), audio input level, BPF settings (frequency, bandwidth, shape), notch filter, CW speed control, and more. These allow for fine-tuning to specific reception statuses.

### Is RST Decoder Pro suitable for beginners?

The app is recommended for practice and checking keying accuracy. While it decodes Morse code, users are advised to try the free version first to understand basic functions before purchasing the Pro version.

### What are the benefits of the Pro version?

The Pro version of RST Decoder Pro includes additional functions such as a waterfall display, which provides a visual representation of the received signal spectrum, enhancing the decoding experience.

### What is the price of RST Decoder Pro?

RST Decoder Pro is a paid application priced at $1.99. It is recommended to try the free version first to ensure it meets your needs before purchasing.

### How often is RST Decoder Pro updated?

The application was last updated on January 23, 2026, indicating a recent development cycle. The current version is 3.0.0.

## Version history (last 5 releases)

### 3.0.0 — 2026-01-23

You can call a decoder that implements the new algorithm.

### 2.1.0 — 2025-12-23

The display method has been upgraded.

### 2.0.0 — 2023-02-15

I reviewed the parameter of the decoder part and improved the performance.

### 1.9.0 — 2023-02-10

Fixed a screen scaling bug on iPhone mini.

### 1.8.0 — 2023-02-05

Adjusted the screen size.

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## More apps by koji kamogawa

- [UkeDrum](https://appshunter.io/ios/app/ukedrum/id1488210714)
- [RST 599](https://appshunter.io/ios/app/rst-599/id1488919851)
- [WabunMorse](https://appshunter.io/ios/app/wabunmorse/id1490745806)
- [音耳せん](https://appshunter.io/ios/app/id1496478545)
- [RST 599 Pro](https://appshunter.io/ios/app/rst-599-pro/id1497452984)
- [RST 599x](https://appshunter.io/ios/app/rst-599x/id1498597799)

All apps by koji kamogawa: https://appshunter.io/developer/1488210713

## Related topics

[rst decoder pro](https://appshunter.io/ios/topics/rst-decoder-pro) · [rst decoder](https://appshunter.io/ios/topics/rst-decoder)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-03.*