Hi Stefan, Edgar,
>> boundary of the garden
fence
Well the signal did end up in a garden fence. Only
this time the garden is on the other side of Earth
;-)
Absolutely impressive and truly groundbreaking work!
Best 73,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: DK7FC <
[email protected]>
An: rsgb_lf_group <
[email protected]>
Verschickt: Fr, 6. Apr 2018 14:07
Betreff: VLF:
Carrier detection DL > VK7 on 17.4701 kHz
Hi VLF,
A few weeks ago i had
the crazy idea to try an attempt to be detected on
17.4701 kHz
in Tasmania / VK7.
Edgar J.T. is the one on the
other side. A few years ago he managed to
detect my DFCW-180
signal on 136 kHz at two different locations. He is
currently
watching ZEVS as well as other special signals on the VLF.
Using an omidirectional whip antenna on his side we attempted to
detect
a pure carrier transmission that was transmitted daily
from my site in
JN49IK00WD, beginning at March, 15th.
Each day i transmitted from 16...23 UTC with about 1 A antenna
current
on my INV-L antenna wire 30m above the ground. My
average ERP estimate
is 2.5 mW on that frequency (average
estimate, not average ERP ;-) ).
At the beginning
there were frequency stability problems on the RX site
but
since the 21st of March the system was running well and stable. So
we could observe a growing SNR during certain times within the
stacked
files.
We ended up
stacking 13 daily transmissions into one file to analyse. I
build a simple script in vlfrx tools to produce a set of data which
was
plotted in Excel. Here is the latest plot:
http://www.iup.uni-heidelberg.de/schaefer_vlf/VLF/DL_VK7_17470.pngThe curves show the SNR of the carrier for different
start times and
durations. The best SNR (12.70 dB in my stack)
is obtained when starting
at 19:20 UTC and watching the signal
in 93 uHz, i.e. 3 hours.
After reaching about 12
dB SNR it became clear that this will become a
successful
detection. So i informed Paul Nicholson to evaluate the files
and asked for a critical comment regarding the significance. He
used his
new fast PC to run a number of permutations of the
files to produce an
even better SNR, by dropping a few days
which do not contribute
positively to the stack. In the end we
ended up at > 14 dB SNR and found
the strongest peak of the
file(s) exactly on the expected frequency.
I
leave it to Paul to present the best spectrum peak and comment further
on the statistical significance of the signal.
BTW this is the path:
http://k7fry.com/grid/?qth=QE37PD&from=JN49IK00WDMy thanks and congratulations go to Edgar J.T. for
the successful
carrier detection and the permanent available RX
system, as well as for
daily providing of the txt files
containing the FFT data. Oh and not to
forget about the
patience :-)
Also thanks to Markus and Paul for the discussion
and support in the
background. And not to forget about DL4YHF
for developing SpecLab, which
is a part of most of these
achievements.
The boundary of the garden fence
has been pushed a little bit more these
days!
73, Stefan
