Translate Morse Code or CW audio to text.
The HotPaw Morse Code Decoder takes audio input from the microphone or headset input on your iPhone or iPad, decodes Morse Code, and displays the results in text form. It includes both automatic decoding of longer clean signals and manual controls to allow the decoding of more difficult signals in QRM. Decoding parameters that can be manually adjusted include the audio frequency of an optional narrow-band DSP filter, the WPM dot/dash speed used for detecting characters, the threshold level of background noise, and whether Farnsworth timing is to be used for detecting spaces between individual characters.
The Morse Code Decoder includes a built-in spectrogram to help determine the audio frequency of the Morse Code tones. You can then use the optional narrow-band audio filter to help filter out background noise. If the audio filter is enabled (frequency lock icon locked), it can be set for frequencies in the range of 400 to 1400 Hz. The filter can also be left off in a wide-band mode (frequency lock icon unlocked). Tap the spectrogram to set the audio filter to the frequency of a selected frequency peak. On the iPhone, tap the lock button to the right of the spectrum graph to toggle the filter off and on.
The Morse code WPM (words per minute) detection speed is automatically adaptive from about 8 to 40 WPM, and can be locked to the current estimated WPM dot speed (WPM lock icon locked). One the iPhone, tap the lock button to the right of the waveform graph to lock and unlock automatic WPM detection. You can also manually set the WPM code speed using the plus and minus symbols that appear in the waveform graph, or the slider control on an iPad. There is a QRQ High Speed WPM Mode which will work better for code speeds in the range of 30 to 80 WPM. (QRQ mode also supports higher frequency dot-dash tones.)
By default, the threshold (the signal level above any background noise required to detect a dot or dash) is set automatically by the AGC. But you can also manually control the threshold setting. On the iPhone or iPod Touch, tap to the left of the waveform graph to switch the manual threshold slider on and off. The iPad version also includes a switch to enable manual threshold control. A Histogram of the tone signal levels with a marker for the detection threshold level are displayed next to the waveform graph.
For best results, make sure the Morse Code tone frequency isn't too high (above 1 kHz), and that the Morse Code speed isn't 3 times or more above or below the WPM settings. Use the manual settings if automatic decoding does not adjust to the frequency, WPM or background noise threshold level properly.
For users who can't get the decoder to start decoding at all, the problem is likely to be an inappropriate audio level, a bit of room echo,
a tone frequency too high, too much background noise,
or some radio noise causing an unrealistic initial WPM setting
at startup. Please see the new help file on the HotPaw website for hints as to how to solve some of these issues.