RST Decoder

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🔧 Utilities

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Updated
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Age Rating
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Data updated
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June 21, 2020
January 23, 2026
3.3.0
iOS 17.0+
4+
ad-supported
5.38MB
iPhone
a month ago
2

Developer

koji kamogawa

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About

This application decodes Morse code from your microphone, acting as a practice tool to verify your keying accuracy. It offers advanced features like BPF and FFT decoders with automatic frequency and gain control, allowing for fine-tuning of reception parameters.

✓Microphone Morse code decoding

✓Morse practice and keying check

✓BPF and FFT decoder options

✓Auto Frequency Detector (AFD)

✓Auto Gain Control (AGC)

✓Real-time CW signal display

✓Input signal recording/playback

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What's New in RST Decoder

3.3.0

January 23, 2026

You can call a decoder that implements the new algorithm.

User reviews

Works well!

After a few minutes to see what it’s all about, it showed the noise and code clearly. A bit of fiddling and I was copying nice code, as well as some pricy software.
Of course, signal fading and bursts of occasional QRM would lose the code as most others also do.
I will work more with this one, and so far I am very satisfied!

Eagleriverprof

4 years ago

Response from developer

Thanks for your comment and five stars. I need a time, but I will try to improve the decoding function.

Idiot hams don’t know how to use it.

If you think that this will copy someone with a bad fist, you’re an idiot. It does well with a strong signal and a good fist, as it should. The two decoding algorithms, Work well, even with QRN. If you don’t like what it does, then decode by ear, but go get a hearing aid, because you can’t hear like you did when you were in your 20s.

rickthedj

4 years ago

Response from developer

Thanks for your comment and five stars.

FFT Addition, great addition.

I am enjoying this CW tool more and more. Thank you for all the thought put into it.

73. ve3myz

nexus6gs [ve3myz]

5 years ago

Response from developer

Thanks for good review. I am trying to improve the algorithm of decoder, stay tuned. ----- I'm glad you're happy. (^_^)

Works great

Works great for practicing and making sure I’m keying right, one thing I would like to see in this app is the ability to have the app in landscape.

Nebben_Almighty

5 years ago

Response from developer

Thanks for your good comments. OK, I will try to study for implementation of the landscape mode. Please wait a while. --- Landscape mode is supported in Ver2.2.0.

Pretty bad

Has potential but it has too much difficulty unless your going extremely slow, at 15 wpm it’s mistaking x for k and y which sound nothing like eachother and t gets mistaken for e and the other way around. Just not viable for anything serious, humans can do it as good or better than this 100% of the time. Maybe if there was a custom wpm option to put in your actual key speed it might have an easier time but I need to pause for about a second between each letter for it to process them. Most people don’t send much slower than 15 wpm so this isn’t the solution to your problems.

sweatlord171

5 years ago

Response from developer

I am very sorry for pretty bad review. At first, you should understand that this App is for a Morse practice App that you can use to check if you are keying the correct code for the Morse Beginner. I understand this app is not for actual operation, and Auto mode of CW Speed algorithm is not enough.For general use, CW Speed of Mid1 or Mid2 is better than Audo. And as you may know the Audio Level detection has bad too. But, I will intend to improve this App a little by bit because of user being.

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