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[195.171.43.25]) by mx.google.com with ESMTP id ge10si1587061wib.108.2014.05.11.04.11.52 for ; Sun, 11 May 2014 04:11:52 -0700 (PDT) Received-SPF: none (google.com: owner-rsgb_lf_group@blacksheep.org does not designate permitted sender hosts) client-ip=195.171.43.25; Authentication-Results: mx.google.com; spf=neutral (google.com: owner-rsgb_lf_group@blacksheep.org does not designate permitted sender hosts) smtp.mail=owner-rsgb_lf_group@blacksheep.org; dkim=pass header.i=@mx.aol.com; dmarc=pass (p=REJECT dis=NONE) header.from=aol.com Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1WjQiw-0001Vf-QA for rs_out_1@blacksheep.org; Sun, 11 May 2014 11:11:14 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1WjQiw-0001VW-4C for rsgb_lf_group@blacksheep.org; Sun, 11 May 2014 11:11:14 +0100 Received: from omr-d01.mx.aol.com ([205.188.252.208]) by relay1.thorcom.net with esmtps (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.82) (envelope-from ) id 1WjQis-0002cm-Qs for rsgb_lf_group@blacksheep.org; Sun, 11 May 2014 11:11:13 +0100 Received: from mtaout-mbc01.mx.aol.com (mtaout-mbc01.mx.aol.com [172.26.221.141]) by omr-d01.mx.aol.com (Outbound Mail Relay) with ESMTP id 1EB7D700000AC for ; Sun, 11 May 2014 06:11:09 -0400 (EDT) Received: from White (95-91-237-52-dynip.superkabel.de [95.91.237.52]) by mtaout-mbc01.mx.aol.com (MUA/Third Party Client Interface) with ESMTPA id 18B9C38000089 for ; Sun, 11 May 2014 06:11:07 -0400 (EDT) Message-ID: From: "Markus Vester" To: References: <536F1A51.3060806@abelian.org> Date: Sun, 11 May 2014 12:11:06 +0200 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 12.0.1606 x-mimeole: Produced By Microsoft MimeOLE V12.0.1606 x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1399803069; bh=pRgr2GNuI8mzpJcnLWZReHgalcC1jyKmmE+dliTdLsk=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=uzUvO/0bzxB+QCFzspkvgy8+Tfyh5mHrBahArXE7HtJyHCH67/efBRAv82uhg51zw J9wuwkruV+pYkRFCZbPc+gQWNtBkfcLWkYVsWpFNnkZlmzMvFNMPGXA8oWfJYlQZN+ c0yfjTHlCr5k0LkAuiO5zYaCOSTsCf9Gu0bzBhu4= x-aol-sid: 3039ac1add8d536f4cbb5e6e X-AOL-IP: 95.91.237.52 X-Spam-Score: -0.6 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Thanks Paul, for devising this experiment in the first place, and encouraging me to take part in it. It looks like we are now getting real close to the ultimate Shannon limit, making best use of your superb receive capabilities. [...] Content analysis details: (-0.6 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [205.188.252.208 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (markusvester[at]aol.com) -0.0 SPF_PASS SPF: sender matches SPF record -0.7 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: f548c2e6c4e712c1eb3dcc8bf83f0d4f Subject: Re: VLF: Coherent BPSK at 8270 from DF6NM Content-Type: multipart/alternative; boundary="----=_NextPart_000_0033_01CF6D12.162CAFE0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.6 required=5.0 tests=HTML_20_30,HTML_MESSAGE, MAILTO_TO_SPAM_ADDR,MISSING_OUTLOOK_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false Dies ist eine mehrteilige Nachricht im MIME-Format. ------=_NextPart_000_0033_01CF6D12.162CAFE0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Thanks Paul, for devising this experiment in the first place, and = encouraging me to take part in it. It looks like we are now getting real = close to the ultimate Shannon limit, making best use of your superb = receive capabilities. The transmit hardware setup is similar to the previously used one, with = a couple of minor extensions. Here are some pictures: = df6nm.bplaced.net/VLF/pictures/VLF_PSK_140510/=20 The 8270 Hz carrier comes from a Rubidium-referenced decadic = synthesizer, with frequency calibrated to Loran-C to within about 1e-10. = For the test, an encoded bit sequence for the five-character message was = obtained beforehand from Paul's script on his website. SpecLab's = digimode terminal (configured similar as previously for Opera, and = initiated by "scheduled actions") is used to generate a keyed sidetone, = with bit timing controlled by NTP to within a second. The tone is being = rectified at the soundcard output and drives an ancient and sensitive = telephone relay, commuting the carrier between two complimentary outputs = of a small pot core transformer. The phase-keyed signal is then amplified by the usual "Nitro" audio PA = to about 60 Watts (28 V rms). A large ferrite transformer (in the brown = chocolate box) bought the voltage up to 200 V rms, feeding 0.3 A antenna = current to the venerable seven-bucket coil which is sitting in the blue = rubber bins outside the window. To keep the antenna on resonance, the phase detector from my LF = automatic tuner (basically an XOR comparing the phase of voltage and = current, with sensors modified for the lower frequency) was inserted = between the amp and the transformer. It drives a little DC motor, = pulling on a nylon string, which then rotates a 10x10x0.5 cm^3 ferrite = plate inside the coil. This effectively mitigates current reductions and = phase variations caused by wind, temperature and humidity. During = operation, one can hear the whistle of the coil and transformers, = occasionally interrupted by a short "krk" sound when the relay is = bouncing during phase changes at full or half minute. All the best, 73, Markus (DF6NM) =20 From: Paul Nicholson=20 Sent: Sunday, May 11, 2014 8:36 AM To: rsgb_lf_group@blacksheep.org=20 Subject: VLF: Coherent BPSK at 8270 from DF6NM I am pleased to report reception of two test transmissions from DF6NM on 8270.000 Hz which took place on Saturday 2014-05-10 morning. Markus was sending coherent BPSK with UT synchronous symbols using a symbol period of 30 seconds. The FEC is a terminated rate 1/4 convolutional code with constraint length 21, cascaded with an outer error detecting code using a 16 bit CRC. Two transmissions of 46 bits were made, each lasting 132 minutes with a 20 minute carrier test in between. ERP was probably around 5 or 10 uW and the range is 1028 km. Eb/N0 was about -0.5dB in the first test and about -1.5 dB in the second, which is below -7dB in the symbol bandwidth of 33.3 mHz. Both messages were decoded with some margin to spare. The decoder is a list Viterbi decoder using the tree trellis algorithm with a list length of 2000 and stack size 20000. Both messages decoded at the top of the list so the list decoding wasn't actually necessary for this strength of signal. The transmitter uses a rubidium source and the receiver is GPS timed. A reference phase at the receiver is obtained by averaging the phase of the squared signal but at such low signal strengths the resulting reference is unreliable and the decoder makes a search for the correct phase and phase drift rate. The signal is completely invisible in any spectrogram at the receiver. In a spectrogram running at the symbol bandwidth the signal is too far below noise and the bandwidth of the transmission is such that, in a resolution capable of seeing the signal above noise, the signal is too wide. For example, this spectrogram uses the symbol bandwidth, http://abelian.org/vlf/tmp/df6nm_140510a.png Maybe someone can see some very faint line at 8270.000 ? The first test ran 07:02 to 09:12 and the second from 09:32 to 11:44. The 20 minute carrier in between is also below noise at this resolution. Following the second test, an hour of carrier is visible in the 278 uHz spectrogram at http://abelian.org/vlf/fbins.shtml#p=3D1399780800&b=3D110&s=3Dsp More information on the FEC codes, trials, and search for good polynomials can be found at http://abelian.org/fec Stronger codes with constraint length up to 25 are available and hopefully further tests will be made soon. -- Paul Nicholson -- ------=_NextPart_000_0033_01CF6D12.162CAFE0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks Paul, for devising this experiment in the first place, and encouraging me = to take=20 part in it. It looks like we are now getting real = close to the ultimate Shannon limit, making best use = of your=20 superb receive capabilities.
 
The transmit hardware setup is = similar to the=20 previously used one, with a couple of minor extensions. Here are = some=20 pictures: df6nm.bpla= ced.net/VLF/pictures/VLF_PSK_140510/ 
 
The 8270 Hz carrier comes from a=20 Rubidium-referenced decadic synthesizer, with frequency calibrated to=20 Loran-C to within about 1e-10. For the test, an encoded bit sequence for the five-character message=20 was obtained beforehand from Paul's script on his=20 website. SpecLab's digimode terminal (configured similar = as previously=20 for Opera, and initiated by "scheduled actions") is used to = generate a=20 keyed sidetone, with bit timing controlled by NTP to within a second.=20 The tone is being rectified at the = soundcard=20 output and drives an ancient and sensitive telephone relay, = commuting=20 the carrier between two complimentary outputs of a small pot core=20 transformer.
 
The phase-keyed signal is then = amplified=20 by the usual "Nitro" audio PA to about 60 Watts (28 V=20 rms). A large ferrite transformer (in the brown chocolate = box) bought the voltage up to 200 V rms, feeding 0.3 = A=20 antenna current to the venerable seven-bucket coil which = is sitting in=20 the blue rubber bins outside the window.
 
To keep the antenna on resonance, the = phase=20 detector from my LF automatic tuner (basically an XOR comparing the = phase=20 of voltage and current, with sensors modified for the lower = frequency)=20 was inserted between the amp and the transformer. It drives a little DC motor, pulling on a nylon string, = which then=20 rotates a 10x10x0.5 cm^3 ferrite plate inside the coil.=20 This effectively mitigates current reductions and phase = variations=20 caused by wind, temperature and humidity. During=20 operation, one can hear the whistle of the coil and transformers,=20 occasionally interrupted by a short "krk" sound when the relay is = bouncing=20 during phase changes at full or half minute.
 
All the best,
73, Markus (DF6NM)

 
Sent: Sunday, May 11, 2014 8:36 AM
Subject: VLF: Coherent BPSK at 8270 from = DF6NM

I=20 am pleased to report reception of two test transmissions from
DF6NM = on=20 8270.000 Hz which took place on Saturday = 2014-05-10
morning.

Markus=20 was sending coherent BPSK with UT synchronous symbols
using a symbol = period=20 of 30 seconds.  The FEC is a terminated rate
1/4 convolutional = code with=20 constraint length 21, cascaded
with an outer error detecting code = using a 16=20 bit CRC.

Two transmissions of 46 bits were made, each lasting=20 132
minutes with a 20 minute carrier test in between.  ERP=20 was
probably around 5 or 10 uW and the range is 1028 km.

Eb/N0 = was=20 about -0.5dB in the first test and about -1.5 dB
in the second, which = is=20 below -7dB in the symbol bandwidth
of 33.3 mHz.

Both messages = were=20 decoded with some margin to spare.

The decoder is a list Viterbi = decoder=20 using the tree trellis
algorithm with a list length of 2000 and stack = size=20 20000.
Both messages decoded at the top of the list so the = list
decoding=20 wasn't actually necessary for this strength of signal.

The = transmitter=20 uses a rubidium source and the receiver is
GPS timed.   A = reference=20 phase at the receiver is obtained by
averaging the phase of the = squared=20 signal but at such low signal
strengths the resulting reference is = unreliable=20 and the decoder
makes a search for the correct phase and phase drift=20 rate.

The signal is completely invisible in any spectrogram at=20 the
receiver.   In a spectrogram running at the symbol=20 bandwidth
the signal is too far below noise and the bandwidth of=20 the
transmission is such that, in a resolution capable of = seeing
the=20 signal above noise, the signal is too wide.

For example, this = spectrogram=20 uses the symbol bandwidth,

  http://abelian.org/= vlf/tmp/df6nm_140510a.png

Maybe=20 someone can see some very faint line at 8270.000 ?

The first test = ran=20 07:02 to 09:12 and the second
from 09:32 to 11:44.   The 20 = minute=20 carrier in between is
also below noise at this = resolution.

Following=20 the second test, an hour of carrier is visible in
the 278 uHz = spectrogram=20 at

  http://abelian.org/vlf/fbins.shtml#p=3D1399780800&b=3D110&am= p;s=3Dsp

More=20 information on the FEC codes, trials, and search for
good polynomials = can be=20 found at

  http://abelian.org/fec

Stronge= r codes=20 with constraint length up to 25 are available
and hopefully further = tests=20 will be made soon.
--
Paul Nicholson
--

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