From: <hvanesce@comcast.net>
To: <rsgb_lf_group@blacksheep.org>
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Date: Sun, 25 Dec 2016 16:46:43 -0500
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Subject: RE: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz
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Wow!

Fine work, quite an accomplishment in many respects.

I cheered in private.

Thank you Stefan and Paul.

Jim AA5BW

-----Original Message-----
From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Paul Nicholson
Sent: Sunday, December 25, 2016 2:05 PM
To: rsgb_lf_group@blacksheep.org
Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz


Some figures.

Average S/N: -60.7dB in 2.5kHz after sferic blanking;

Information bits: 427.5  (5.7 bits per character); Code symbols: 3872; Overall code rate: 1/9.057; Total duration: 189728 seconds;

Info bit rate: 8.11 bits per hour (76% of channel capacity);

With such long messages, it isn't necessary to use a CRC.
The redundant 0.3 bits per character add up to 22.5 bits which is plenty enough for the outer error detection layer to use.

With 22.5 plus the default 16 bit CRC, the optimum list length for the outer layer is impractical and we don't get the full coding gain.

On the Linux version you can set CRC size to zero to turn it off, I'm not sure the Windows version will accept zero.

--
Paul Nicholson
--