Message-ID: <548D6237.5060400@abelian.org>
Date: Sun, 14 Dec 2014 10:11:03 +0000
From: Paul Nicholson <vlf0403@abelian.org>
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CC: Renato Romero <contact@vlf.it>
References: <548B3BA6.5050907@gmail.com> <548BB9F7.80007@gmail.com> <548CA421.1080905@abelian.org> <025901d01728$41a8da20$c4fa8e60$@comcast.net>
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Subject: Re: LF: Re: 8957 Hz
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Status: O


Last night Dex was testing at 9177 Hz.

W4DEX at Todmorden and Bielefeld (DL4YHF) in 1 hour steps
at 9177 Hz:

  Start    Todmorden        Bielefeld
           S/N    Phase     S/N    Phase

  22:00   10.4dB  -39.3     5.8dB  -62.2
  22:30   11.7dB  -56.9     3.3dB
  23:00    8.6dB  -85.3     2.6dB
  23:30    5.7dB  -85.6     4.1dB  -74.3
  00:00    8.9dB  -74.6     2.6dB  -96.9
  00:30   11.9dB  -86.8    -2.5dB
  01:00   10.2dB  -91.1    -6.0dB
  01:30    7.9dB  -84.1     4.0dB  -14.1
  02:00    6.0dB  -51.5     5.2dB  -38.4
  02:30    5.5dB  -59.5     1.2dB
  03:00    4.9dB  -92.4     2.1dB

Really, there is nothing significant at all at Bielefeld, I
tried a range of times bandwidths but couldn't pull anything
out of the noise to measure.

Average at Todmorden 22:00 to 02:00 0.20 fT (equiv 60nV)
                      22:00 to 04:00 0.16 fT (equiv 48nV)

Max signal bearing 290, max S/N bearing 310 was 15.7dB
in 46uHz.

H-field spectrum

    http://abelian.org/vlf/tmp/141214b.gif

E-field spectrum

    http://abelian.org/vlf/tmp/141214c.gif

with grossly incorrect calibration thanks to a herd of cows.
(This is the old E-field rx, the new one is sat in the corner of
my office having disgraced itself in a recent near-field test).

Combining E and H coherently gives 18.0db S/N.

    http://abelian.org/vlf/tmp/141214d.gif

Last night was perhaps overall the best so far from Dex, signal
was 1.3dB stronger than the previous night at 8957Hz but the
background noise was higher too.  Looking at those plots and
the stable phase you would think there is quite a bit in hand
with which to push further into Europe.  You could lose 6dB
off the signal and still get a clear detection - that's a
margin that gets you at least another 1000km overland.

At Cumiana Italy, the online receiver run by Renato Romero IK1QFK,
produced this interesting peak in the spectrum,

    http://abelian.org/vlf/tmp/141214e.gif

It is visible in wider bandwidths too and improves towards 04:00.
Previous night at 8957Hz turned up nothing at all.  The S/N is about
what we would expect given the extra distance to Cumiana (7173km).
I'll be having a closer look at this, expect a follow-up post in a
couple of hours.

At Forest VA:

  http://abelian.org/vlf/tmp/141214a.png

  UT     S/N     Phase
  21:40  12.2dB   10.8
  22:00  13.7dB   -2.8
  22:20  15.3dB   14.3
  22:40  18.0dB   19.2
  23:00  16.1dB   14.0
  23:20  16.1dB   -2.3
  23:40  17.0dB  -10.8
  00:00  18.3dB   -3.6
  00:20  18.5dB   -1.7
  00:40  18.6dB    7.4
  01:00  18.9dB    3.5
  01:20  17.3dB   -7.0
  01:40  18.7dB  -12.5
  02:00  20.6dB    2.0
  02:20  18.3dB   -1.5
  02:40  17.9dB    5.9
  03:00  18.9dB    2.7
  03:20  18.6dB    5.8
  03:40  20.2dB    9.8

With such a strong and stable signal you could reliably
send over 150 bits per hour.
--
Paul Nicholson
--