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Re: LF: Bugfix for ebnaut_ifft utility

To: [email protected]
Subject: Re: LF: Bugfix for ebnaut_ifft utility
From: DK7FC <[email protected]>
Date: Wed, 07 Jun 2017 18:47:42 +0200
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Thanks Markus,

What does minor SNR degradation mean, in dB, and on what does this value depend? (e.g. transmission time, symbol length, etc).

73, Stefan

Am 07.06.2017 17:59, schrieb Markus Vester:

Dear EbNauteers,

I recently stumbled upon a bug in my ebnaut_ifft3a utility, which is used to convert SpecLab FFT export files to IQ wav files. The first step of the inverse FFT is to take the complex conjugate of the data array. Due to the bug, the respective loop was executed only N-1 times, leaving a sign error in the imaginary part of a single bin next to the center frequency. When fed with a high-SNR signal close to SpecLab's center frequency, this can produce strange undulation patterns in the phase display and a minor SNR degradation for the decoder.

The bug has been fixed in version 3b, available on
 http://df6nm.bplaced.net/VLF/fec_tests/ebnaut_ifft3b.zip

Best regards,
Markus (DF6NM)

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