Message-ID: <4CB4BAF8.80903@iup.uni-heidelberg.de>
Date: Tue, 12 Oct 2010 21:46:00 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
CC: Paul <paul@abelian.netcom.co.uk>, Renato Romero <contact@vlf.it>
References: <8CD38567F4B0C6A-1C1C-116D@webmail-m021.sysops.aol.com>
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Subject: Re: VLF: Detections of 5 microwatt transmission
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Hi Markus and Paul,

Congratulations to this remarkable success! It seems almost impossible 
that this is possible ;-)

Now we know that many amateurs could get a reception of their signals, 
transmitted on the Dreamers Band. It takes a long time for this 
detection but usually we have enough time, isn't it?
Furthermore it confirms that we (or Paul) can calculate and compare 
signal levels and thus the antenna efficiency of a unknown antenna can 
be calculated or estimated (e.g. if trees are near the antenna and cause 
a unknown efficiency reduction). This fact is very interesting and 
important for transmissions on my earth antenna! I will try to leave a 
trace there as well. Additionaly we can make tests to do some research 
of VLF propagation on ~ 9 kHz!

Even lower ERP tests could be done. Your transmission took about 8 hours 
at 80 W TX power(?). If one is using 10 W TX power (reducing the noise 
and the high voltage and the risk of a burn!) and the integration time 
would be 64 hours, could the S/N become the same?

All in all very interesting and a nice step forward in exploring the 
Dreamers Band! Thanks Markus!

73, Stefan/DK7FC



Am 12.10.2010 20:57, schrieb Markus Vester:
>
> Dear LF,
> for my VLF test transmissions on the last weekend (Oct 9: 8969.998 Hz, 
> Oct. 10: 8989.997 Hz), I have received reports from three receiving 
> stations:
> - Walter DJ2LF near Erlangen (20.2 km) received the carrier again in 
> good quality, using 0.95 mHz resolution. Radiated power and received 
> SNR were quite similar to our two-way QSO on June 4th.
> - Stefan DK7FC in Heidelberg (178.5 km) reported about 10 dB SNR, and 
> both dashes are still visible in the QRN minima on his 47uHz grabber 
> window
> http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html
> This was the intended purpose of the experiment, and a nice 
> counterpart to the earlier detection of a 200 uW kite transmission on 
> Aug 29th. Even though both of us were locking the samplerate to a 10 
> kHz GPS-derived reference, the dashes appeared about two pixels low - 
> perhaps due to a very minute rounding error in SpecLab's frequency 
> scale display.
> - To my utter surprise, Paul Nicholson (Todmorden, 1030.5 km) produced 
> two spectra, taken over the duration of the transmissions:
> http://abelian.org/vlf/df6nm/2010_10_09a.gif   (9:50 - 18:00, 34 uHz)
> http://abelian.org/vlf/df6nm/2010_10_10a.gif   (9:00 - 15:00, 46 uHz)
> After taking a deep breath, we now have to deal with the question 
> whether this is a significant positive detection. Except for a known 
> central artifact on 8970, the highest peak appears in the correct 
> frequency bin in both spectra. Naively, one could then propose that 
> the probability of this happening at random would simply be the 
> inverse of the number of displayed bins, ie. around 1:230 for Saturday 
> and 1:170 for Sunday. Thus the combined probability of a false 
> positive detection on both days would seem to be only 1 in 40000. 
> Certainly there is a degree of arbitrariness in the choice of the 
> display range (8 mHz).
> Paul estimated that the signal was about 3 standard deviations on 
> Saturday (0.3% false detection rate), and 2 sigma in the higher noise 
> on Sunday (5%), giving a combined false positive probability of 1 in 6667.
> We can also look at the plausibility of the absolute fieldstrength of 
> the peaks (about 0.2 fT, equivalent to 0.06 uV/m). If I remember 
> correctly, Paul's first detection of Stefan's kite signal on March 15 
> was at about 3 fT, and Stefan was then radiating approx. 1 mW EMRP. 
> Scaling this down to my estimated 5 uW EMRP, and taking another dB for 
> the slightly higher distance, would theoretically result in 24 dB less 
> fieldstrength, or 0.19 fT - almost a perfect match.
> So by these lines, it would seem at least very likely that Paul has 
> indeed observed my feeble signal! We intend to do repeat the 
> experiment in the near future for additional confirmation.
> Very many thanks to all involved in this work!
> 73, Markus (DF6NM)

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Hi Markus and Paul,<br>
<br>
Congratulations to this remarkable success! It seems almost impossible
that this is possible ;-) <br>
<br>
Now we know that many amateurs could get a reception of their signals,
transmitted on the Dreamers Band. It takes a long time for this
detection but usually we have enough time, isn't it?<br>
Furthermore it confirms that we (or Paul) can calculate and compare
signal levels and thus the antenna efficiency of a unknown antenna can
be calculated or estimated (e.g. if trees are near the antenna and
cause a unknown efficiency reduction). This fact is very interesting
and important for transmissions on my earth antenna! I will try to
leave a trace there as well. Additionaly we can make tests to do some
research of VLF propagation on ~ 9 kHz! <br>
<br>
Even lower ERP tests could be done. Your transmission took about 8
hours at 80 W TX power(?). If one is using 10 W TX power (reducing the
noise and the high voltage and the risk of a burn!) and the integration
time would be 64 hours, could the S/N become the same?<br>
<br>
All in all very interesting and a nice step forward in exploring the
Dreamers Band! Thanks Markus!<br>
<br>
73, Stefan/DK7FC<br>
<br>
<br>
<br>
Am 12.10.2010 20:57, schrieb Markus Vester:
<blockquote   cite="mid:8CD38567F4B0C6A-1C1C-116D@webmail-m021.sysops.aol.com"   type="cite"><font color="black" face="arial" size="2">
  <div><br>
Dear LF,</div>
  <div>&nbsp;</div>
  <div>for my VLF test transmissions on the last weekend (Oct 9:
8969.998 Hz, Oct. 10: 8989.997 Hz), I have received reports from three
receiving stations:</div>
  <div>&nbsp;</div>
  <div>- Walter DJ2LF near Erlangen (20.2 km) received the carrier
again in good quality, using&nbsp;0.95 mHz resolution. Radiated power and
received SNR were quite similar to our two-way QSO on June 4th.</div>
  <div>&nbsp;</div>
  <div>- Stefan DK7FC in Heidelberg (178.5 km) reported about 10 dB
SNR, and both dashes are still visible in the QRN minima on his 47uHz
grabber window </div>
  <div>&nbsp;</div>
  <div><a moz-do-not-send="true"   href="http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html">http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html</a></div>
  <div>&nbsp;</div>
  <div>This was the&nbsp;intended purpose of the experiment, and&nbsp;a nice
counterpart to the earlier detection of a 200 uW kite transmission on
Aug 29th. Even though both of us were locking the samplerate to a 10
kHz GPS-derived reference, the dashes appeared about&nbsp;two pixels low -
perhaps due to a very minute rounding error in SpecLab's frequency
scale display.</div>
  <div>&nbsp;</div>
  <div>- To my utter surprise, Paul Nicholson (Todmorden, 1030.5
km)&nbsp;produced two spectra, taken over the duration of the transmissions:</div>
  <div>&nbsp;</div>
  <div>&nbsp;&nbsp; <a moz-do-not-send="true"   href="http://abelian.org/vlf/df6nm/2010_10_09a.gif">http://abelian.org/vlf/df6nm/2010_10_09a.gif</a>&nbsp;&nbsp;
(9:50 - 18:00, 34 uHz)<br>
&nbsp;&nbsp; <a moz-do-not-send="true"   href="http://abelian.org/vlf/df6nm/2010_10_10a.gif">http://abelian.org/vlf/df6nm/2010_10_10a.gif</a>&nbsp;&nbsp;
(9:00 - 15:00, 46 uHz)</div>
  <div>&nbsp;</div>
  <div>After taking a deep breath, we now have to deal with the
question whether this is a significant positive detection. Except for a
known central artifact on 8970, the highest peak appears in the correct
frequency bin in both spectra. Naively, one could then propose that the
probability of this happening at random would simply be the inverse of
the number of displayed bins, ie. around 1:230 for Saturday and 1:170
for Sunday. Thus the combined probability of a false positive detection
on both days would seem to be only 1 in 40000. Certainly there is a
degree of arbitrariness in the choice of the display range (8 mHz).</div>
  <div>&nbsp;</div>
  <div>Paul estimated that the signal was about 3 standard deviations
on Saturday (0.3% false detection rate), and 2 sigma in the higher
noise on Sunday (5%), giving a combined false positive probability of 1
in 6667.</div>
  <div>&nbsp;</div>
  <div>We can also look at the plausibility of the absolute
fieldstrength of the peaks (about 0.2 fT, equivalent to 0.06 uV/m). If
I remember correctly, Paul's first detection of Stefan's kite signal on
March 15 was at about 3 fT, and Stefan was then radiating approx. 1 mW
EMRP. Scaling this down to my estimated 5 uW EMRP, and taking another
dB for the slightly higher distance, would theoretically result in 24
dB less fieldstrength, or 0.19 fT - almost a perfect match.</div>
  <div>&nbsp;</div>
  <div>So by these lines, it would seem at least very likely that Paul
has indeed observed my feeble signal! We intend to do repeat the
experiment in the near future for additional confirmation.</div>
  <div>&nbsp;</div>
  <div>Very many thanks to all involved in this work!</div>
  <div>&nbsp;</div>
  <div>73, Markus (DF6NM)<br>
  </div>
  </font>
</blockquote>
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