Message-ID: <5B868DB0.4080209@posteo.de>
Date: Wed, 29 Aug 2018 14:12:32 +0200
From: DK7FC <selberdenken@posteo.de>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <1658523aabb-1ec0-b2@webjasstg-vab44.srv.aolmail.net>
In-Reply-To: <1658523aabb-1ec0-b2@webjasstg-vab44.srv.aolmail.net>
Subject: Re: VLF: New experiments on 17.47 kHz planned...
Content-Type: multipart/alternative;
 boundary="------------080705040804020308060905"
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

This is a multi-part message in MIME format.
--------------080705040804020308060905
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

PS: Ah, you decoded the message. That's fine because i didn't know yet 
if all worked well. What was the carrier S/N?

73, Stefan

Am 29.08.2018 12:03, schrieb Markus Vester:
> Hi Stefan and Edgar,
>
> I am still deeply impressed by your groundbreaking work. With close to 
> 12 dB SNR after three nights, it looks like you could chat at a rate 
> of one character per day.
>
> The Excel plots are a nice way to observe the carrier with different 
> integration times and optimize time and bandwidth. It looks like there 
> is another weaker maximum after 21 UT, shortly after sunrise in Hobart 
> (now 20:41 UT).
> For a more intuitive interpretation, I would suggest to plot the 
> middle of the integration time rather than the start time on the x 
> axis, i.e. offset each curve to the right by half the duration. Then 
> all curves should more or less peak at the time of a propagation 
> maximum. There may also be a minor offset in the SNR scale because the 
> noise power is slightly underestimated due to rolloff of SpecLab's 
> decimation filter, I think the carrier SNR is really about 0.8 dB 
> lower than indicated on the y axis.
>
> The NWC phase plot at DL0AO shows a negative phase slope around -45° 
> per hour, so it may be worth to also plot SNR with a small negative 
> frequency offset (~ -35 uHz), possibly gaining a bit more at long 
> integration times.
>
> After decoding your message, I have set up the DL0AO 17.47 kHz 
> instance to unspread the PSK, so it may be used as a local control of 
> transmit phase and sequence timing.
>
> Good luck!
> Markus
>
>
> -----Ursprüngliche Mitteilung-----
> Von: DK7FC <selberdenken@posteo.de>
> An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
> Verschickt: Mo, 27. Aug 2018 15:12
> Betreff: Re: VLF: New experiments on 17.47 kHz planned...
>
> Hi VLF,
>
> After transmitting carriers for the last 5 days, there are 3 good days 
> to stack, the others were noisy.
> The resulting SNR via start time plot for different carrier length is 
> attached. With some uncertainty we can say that these days the ideal 
> start time for the path from DL to VK7 is 17:50 UTC and the message 
> duration should be between 2.5...3 hours.
>
> This evening i'm going to start an attempt for a 2 character EbNaut 
> message. With some luck, just 2 days, i.e. 2 stacks will be enough to 
> get a clear decode.
>
> *f = 17470.1000 Hz
> Start time: 27.Aug.2018  17:50:00 UTC (daily)
> Symbol period: 12 s
> Characters: 2
> CRC bits: 23
> Coding 16K21A
> Duration: 02:56 [hh:mm]
> Antenna current: 1.2 A*
>
>
> 73, Stefan
>
>
>
>
> Am 24.08.2018 14:02, schrieb DK7FC:
>
>     Hi Edgar,
>
>     Thanks for the spectrogram showing JXN nicely! Here i'm watching
>     NWC but the SNR is much lower, probably due to the strong QRN we
>     still have in late August...
>     I'm going to calculate the weighting factors for the stacking
>     based on the noise amplitude from 18...21 UTC. And obviously it is
>     not necessary to transmit until 0 UTC, so i will stop an hour
>     earlier from now on.
>
>     Your SpecLab settings are fine as they are. There is no advantage
>     from a shorter and wider FFT. The observed spectrum width
>     currently allows to display more than 2000 FFT bins centered on
>     the TX frequency, allowing to display enough noise arround the
>     peak to demonstrate that the peak is most unlikely a by-chance peak...
>
>     Thanks for last nights txt file. We can produce a first stack from
>     the two days. Last night is weighted by -1.3 dB. The result is
>     attached. We can already see a peak of 11.3 dB SNR, not
>     unrealistic but still not significant enough. The spectrum peak
>     produced from the suggestion of the Excel plot (Start 17:50 UTC,
>     duration 2 hours) is attached as well. It shows a higher SNR,
>     which depends on the noise floor calculation (0 dB line). I need
>     to work on this but anyway the peak looks good relative to the
>     noise already.
>
>     Another carrier will follow tonite.
>
>     73, Stefan
>
>
>
>     Am 23.08.2018 23:40, schrieb Edgar:
>
>         Hi Stefan,
>
>         Based on the past two days signal from JXN, would it improve
>         the chance of detecting the carrier if the "FFT window time
>         (length)" matched the time when the signal is at maximum?
>
>         The FFT length is now 8.847 hours. The period when JXN signal
>         is white is about 1.5 hours.
>
>         The FFT bin width would be wider, and a larger percentage of
>         bins would have a stronger signal.
>
>
>

--------------080705040804020308060905
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
PS: Ah, you decoded the message. That's fine because i didn't know yet
if all worked well. What was the carrier S/N?<br>
<br>
73, Stefan<br>
<br>
Am 29.08.2018 12:03, schrieb Markus Vester:
<blockquote
 cite="mid:1658523aabb-1ec0-b2@webjasstg-vab44.srv.aolmail.net"
 type="cite">
  <div
 style="font-size: 10pt; font-family: arial,helvetica,sans-serif; color: black;">
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;">Hi
Stefan and Edgar,</div>
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br>
I am still deeply impressed by your groundbreaking work. With close to
12 dB SNR after three nights, it looks like you could chat at a rate of
one character per day.</div>
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br>
The Excel plots are a nice way to observe the carrier with different
integration times and optimize time and bandwidth. It looks like there
is another weaker maximum after 21 UT, shortly after sunrise in Hobart
(now 20:41 UT).</div>
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;">For
a more intuitive interpretation, I would suggest to plot the middle of
the integration time rather than the start time on the x axis, i.e.
offset each curve to the right by half the duration. Then all curves
should more or less peak at the time of a propagation maximum. There
may also be a minor offset in the SNR scale because the noise power is
slightly underestimated due to rolloff of SpecLab's decimation filter,
I think the carrier SNR is really about 0.8 dB lower than indicated on
the y axis. </div>
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br>
The NWC phase plot at DL0AO shows a negative phase slope around -45°
per hour, so it may be worth to also plot SNR with a small negative
frequency offset (~ -35 uHz), possibly gaining a bit more at long
integration times.</div>
  <div
 style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br>
After decoding your message, I have set up the DL0AO 17.47 kHz instance
to unspread the PSK, so it may be used as a local control of transmit
phase and sequence timing.<br>
 <br>
Good luck!<br>
Markus<br>
  <br>
  <br>
-----Ursprüngliche Mitteilung----- <br>
Von: DK7FC <a class="moz-txt-link-rfc2396E" href="mailto:selberdenken@posteo.de">&lt;selberdenken@posteo.de&gt;</a><br>
An: rsgb_lf_group <a class="moz-txt-link-rfc2396E" href="mailto:rsgb_lf_group@blacksheep.org">&lt;rsgb_lf_group@blacksheep.org&gt;</a><br>
Verschickt: Mo, 27. Aug 2018 15:12<br>
Betreff: Re: VLF: New experiments on 17.47 kHz planned...<br>
  <br>
  </div>
  <div id="AOLMsgPart_1.2_6f301457-d8f8-4149-a245-02d5ae9f7676">
  <div class="aolReplacedBody" text="#000000" bgcolor="#ffffff">Hi VLF,
  <br>
  <br>
After transmitting carriers for the last 5 days, there are 3 good days
to stack, the others were noisy. <br>
The resulting SNR via start time plot for different carrier length is
attached. With some uncertainty we can say that these days the ideal
start time for the path from DL to VK7 is 17:50 UTC and the message
duration should be between 2.5...3 hours.<br>
  <br>
This evening i'm going to start an attempt for a 2 character EbNaut
message. With some luck, just 2 days, i.e. 2 stacks will be enough to
get a clear decode.<br>
  <br>
  <b>f = 17470.1000 Hz<br>
Start time: 27.Aug.2018  17:50:00 UTC (daily)<br>
Symbol period: 12 s<br>
Characters: 2<br>
CRC bits: 23<br>
Coding 16K21A<br>
Duration: 02:56 [hh:mm] <br>
Antenna current: 1.2 A</b><br>
  <br>
  <br>
73, Stefan<br>
  <br>
  <br>
  <br>
  <br>
Am 24.08.2018 14:02, schrieb DK7FC:
  <blockquote cite="about:blank"> Hi Edgar, <br>
    <br>
Thanks for the spectrogram showing JXN nicely! Here i'm watching NWC
but the SNR is much lower, probably due to the strong QRN we still have
in late August...<br>
I'm going to calculate the weighting factors for the stacking based on
the noise amplitude from 18...21 UTC. And obviously it is not necessary
to transmit until 0 UTC, so i will stop an hour earlier from now on.<br>
    <br>
Your SpecLab settings are fine as they are. There is no advantage from
a shorter and wider FFT. The observed spectrum width currently allows
to display more than 2000 FFT bins centered on the TX frequency,
allowing to display enough noise arround the peak to demonstrate that
the peak is most unlikely a by-chance peak...<br>
    <br>
Thanks for last nights txt file. We can produce a first stack from the
two days. Last night is weighted by -1.3 dB. The result is attached. We
can already see a peak of 11.3 dB SNR, not unrealistic but still not
significant enough. The spectrum peak produced from the suggestion of
the Excel plot (Start 17:50 UTC, duration 2 hours) is attached as well.
It shows a higher SNR, which depends on the noise floor calculation (0
dB line). I need to work on this but anyway the peak looks good
relative to the noise already.<br>
    <br>
Another carrier will follow tonite.<br>
    <br>
73, Stefan<br>
    <br>
    <br>
    <br>
Am 23.08.2018 23:40, schrieb Edgar:
    <blockquote cite="about:blank"> <span style="font-family: Arial;"
 data-mce-style="font-family: Arial;" face="Arial">Hi Stefan,<br>
      <br>
Based on the past two days signal from JXN, would it improve the chance
of detecting the carrier if the "FFT window time (length)" matched the
time when the signal is at maximum?<br>
      <br>
The FFT length is now 8.847 hours. The period when JXN signal is white
is about 1.5 hours.<br>
      <br>
The FFT bin width would be wider, and a larger percentage of bins would
have a stronger signal.<br>
      <br>
      </span>
      <div id="aolmail_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
      </div>
    </blockquote>
  </blockquote>
  </div>
  </div>
  <br>
  </div>
</blockquote>
</body>
</html>

--------------080705040804020308060905--