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Original Article

Performance of Electronic Morse Decoders in Decoding Telegraphy Masked by Noise

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Pages 57-62 | Received 10 Jan 1994, Accepted 05 Apr 1994, Published online: 12 Oct 2009
 

Abstract

The performance of five different electronic Morse decoders in decoding telegraphy signs (Morse code) consisting of 800 Hz pure tones masked by a narrow-band noise with a bandwidth of 185 Hz (1/3 octave 713-890 Hz) centred at 800 Hz and a broadband noise (100-2500 Hz) was studied at 20, 40, 80, 150 and 200 signs/min telegraphy speed. In steps of 1 dB the S/N ratios were varied from high values where 100% was recognized to low values where nothing was recognized. At narrow-band masking noise with 80 and 150 signs/min telegraphy speed a S/N ratio varying from +8 to + 12 dB and +8 to +11 dB respectively was required for 100% recognition. At broad-band masking noise the S/N ratios required for 100% recognition varied from -4 to +3 dB at 80 signs/min telegraphy speed and -3 to +3 dB at 150 signs/min telegraphy speed. When compared to earlier findings in our laboratory concerning human recognition of Morse signs it seems that man outperforms electronic Morse decoders at low S/N ratios and low to moderate telegraphy speeds (< 100 signs/min).

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