Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: NA VLF

To: [email protected]
Subject: Re: LF: NA VLF
From: Paul Nicholson <[email protected]>
Date: Tue, 9 May 2017 10:26:45 +0000
Dkim-signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=abelian.org ; s=default; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:To:Subject:Sender:Reply-To:Cc: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=usdnqmHbu6+EUEFPtPPXzff75tM4F+YIqxMBZo8k0T4=; b=3HDKv/qKjEcn1DwLRKqSh2Z8ot T3ExjA+jz3KAJ0vJG4045TS67sFD39i1Rm6mxuHItN5DwiS610Ufv6vTzMpSLzP+br++y08K6+0tB Ufh+tw3wCPPu9ONxZie0OP7nWkY+PP8J8Yeg/1aAdpNyLg4EHzpnlw/r1ZOYjmrMTlDE=;
In-reply-to: <[email protected]cal>
References: <[email protected]cal>
Reply-to: [email protected]
Sender: [email protected]
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1
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:

 http://abelian.org/vlf/tmp/170509a.png

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:

 http://abelian.org/vlf/tmp/170509b.png

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
gives

 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
decode.
--
Paul Nicholson
--

<Prev in Thread] Current Thread [Next in Thread>