New Version 1.3 - with PPC 2002 & PPC 2003 support.
PocketMorse is a utility for decoding Morse Code audio signals. It runs on Pocket PC devices with the Pocket PC 2003 or 2002 operating system or Windows XP desktop systems (equipped with a soundcard). The Morse Code signal is either taken from the microphone input on the PocketPC/desktop or from a Line input (desktop).

Features

• The Scrolling Decoder Window shows a complete history of the Morse Code received, and how the characters have been converted to text. Each Morse character in the Window is delimited by a vertical bar "|". When a word is complete, a new line is started.
• The Text Output Ticker shows the most recent decoded text stream (without the Morse). As more text is received, the text is moved to the left.
• The Statistics and Information Window shows some useful data about how the decoder is functioning:
  • S/N: The Signal to Noise ratio is a dB measurement of the loudest detected audio level against the lowest detected audio level. The decoder will not attempt to extract Morse from a signal having S/N
  • D: The currently measured length of a Morse "dot", in samples. PocketMorse records at the rate of 8000 samples/second. So a dot length of 800 samples corresponds to a time length of 800/8000 i.e. one tenth of a second. As the decoder detects Morse, it adjusts the dot length according to the sent rate. From the dot length the Words Per Minute value is calculated (see WPM, below).
  • I: The currently measured time between Morse words, in samples. For 1:3:7 Morse code, this should be 7 times the dot length. It can (and does) vary considerably from this in practice.
  • T: The sensitivity threshold. This number can be varied between 0.1 and 0.9 (see Sensitivity below). Its default is 0.5, corresponding to average sensitivity. The sensitivity effectively determines the threshold above which the audio signal is said to be sending a dot or a dash.
  • WPM: This indicates the currently measured Words Per Minute send rate, and is simply computed as 1.2 divided by the dot length (in seconds).
• The Raw Audio Signal is shown as a green trace: this is a plot of the audio samples as picked up by the microphone.
• The Smoothed Input Signal is shown as a red trace. To smooth the raw signal a DSP filter that applies an exponential decay with a time constant of 125 milliseconds is applied. This has the effect of making random noise fluctuations affect the decoder less than if the raw samples were used.
• Cutting across the smoothed signal from left to right is a dashed yellow line that shows the current setting of the Threshold value. Any part of the red curve above the yellow line is decoded as a dot or a dash. The results of the decoding are shown by a series of "*" and "-" symbols at the top of the signal window.
• The complete log of decoded Morse may be saved to a Log file.

Capability
PocketMorse can decode Morse when the signal is reasonably clear, and sent at a usual rate. If the signal is very noisy, faint, or sent very slowly (less than about 5 WPM) or very quickly (more than about 25 WPM) then the results from PocketMorse are unreliable.

Version 1.3: Adds bandpass filters (250Hz, 500Hz and 1kHz) for aiding decoding transmissions with noise.