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Re: LF: my results on VLF 05-08 May 2017

To: [email protected]
Subject: Re: LF: my results on VLF 05-08 May 2017
From: Paul Nicholson <[email protected]>
Date: Thu, 11 May 2017 07:52:44 +0000
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Alex wrote:

> {06 May 18:10 6470.1 2-char} transmissions.


Sorry this one did not decode.  The message is there, at
offset +636 seconds but the Eb/N0 is only -1.6 dB.

Incidentally, the command I use on Linux to decode from these WAV
files is (for the 4-char message)

 dd if=ebnaut06_MAY_0136_8270-1pps.wav bs=1 skip=124 |
   od -v -An -w8 -tfF |
   ebnaut -dp16K21A -N4 -S40 -r0.342935 -PS -c8 -k6 -L100 -v -T1001

'dd' strips off the header by skipping 124 bytes and 'od' converts
the 32 bit IEEE floats to two columns of ASCII numbers for input
to ebnaut.

The 4-char WAV header contained timestamp

  1494010730.79 = 2017-05-05_18:58:50.79

and the message started at

  2017-05-05_19:15 = 1494011700.00

so the start offset for EbNaut should be

  1494011700.00 - 1494010730.79 = 969.21

but the message was found at offset 1001.

For the 2-char

 WAV 1494093574.79  2017-05-06_17:59:34.79
 Msg 1494094200.00  2017-05-06_18:10:00.00

Offset should be: +625.21
Message found at: +636.00

Eb/N0 with the +625.21 drops to -3.7 dB due to the symbol

Paul Nicholson

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