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To: [email protected]
Subject: Re: LF: NA VLF
From: Paul Nicholson <[email protected]>
Date: Tue, 9 May 2017 10:26:45 +0000
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I can't detect any signal from Joe last night
8th/9th 22:00 to 04:00, not a trace - perhaps
the tx has gone off.

After sweeping for optimum settings, I couldn't get
much improvement.

Daytime reception, S/N = 13.5 dB in 23.148 uHz:

Some of the energy is in adjacent bins on this 12
hour integration, the frequency probably drifted
a little, losing a dB or so.

Nighttime, S/N = 14.3 dB in 46.296 uHz:

Tried an EbNaut 'decode' of the 6 hour nighttime
signal.  Unmodulated carrier is a valid message which
decodes to a string of '*' characters. Because of the
linearity of the coding, the performance is representative
of any other message with the same settings.

4 chars 16K25A CRC=12 Symbols = 22 seconds, duration 05:52:00

 rank 946 ber 42.2% '****'

 carrier Eb/N0: -0.1 dB
 carrier S/N: 13.53 dB in 47.3 uHz,
             -29.72 dB in 1Hz,
             -63.70 dB in 2.5kHz

The snag is, this 'decode' is only possible because I could
see the signal and measure its frequency.  A real EbNaut
message is invisible and if the frequency is out by more than
about 5uHz it will not decode.

5 chars should just be possible but I could not get it to
Paul Nicholson

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