Hello Jim!
Am 05.08.2017 20:57, schrieb [email protected]:
Congratulations
Stefan, Markus and DL0AO team!
Is
this the first far-field link between 3.000 kHz and 4.000 kHz?
Yes it is, as far as i know. Or at least it is the first detection over
a distance of > 1 wavelength. The far field begins at 13 km
distance. I doubt that this was done before.
Now the distance is 226 km,
http://k7fry.com/grid/?qth=JN49IK00WD&from=JN59VK53NK or 2.77
wavelengths.
Another
great data point in the previously uncharted and rough terrain of 2 kHz
- 4 kHz, 100 km - 1000 km.
Yes this is certainly an interesting point in the spectrum down to DC
and i am looking forward to see some diurnal signal level changes on
that grabber. At that bandwidth and/or scroll rate and the QRN which
can vary by 20 dB and more it won't be easy to tell to much from the
spectrogram however...
BTW where is Paul and Jacek? Jacek often asked when i will do something
below 5.17 kHz. Now it is the time! But certainly not the best time in
the year for such tests :-)
73, Stefan
Analytical
and computational estimates of path loss 2 kHz - 4 kHz, 100 km - 1000
km are at best somewhat (to considerably) speculative for lack of data,
so I’d venture that the DK7FC/DF6NM/DL0AO team, and all those who
provided receivers, transmitters and processing for prior tests 2 kHz -
6 kHz*, 100 km - 1000 km, have done valuable pioneering work.
(great
work in hardware and processing, and especially pioneering work in
characterization of propagation in a little-understood and
not-too-friendly propagation realm 2 kHz - 4 kHz, 100 km - 1000 km)
From
a spectator’s perspective this is very exciting.
* (5 kHz and 6 kHz tests helping to assess an upper boundary for the
complicated 2 kHz - 4 kHz, 100 km - 1000 km space)
(Much
credit also to transmitter, receiver and processing work at 970 Hz
making the interesting sub-kHz world accessible)
Jim
AA5BW
From:
[email protected]
[mailto:[email protected]] On Behalf Of Markus
Vester
Sent: Saturday, August 5, 2017 8:35 AM
To: [email protected]
Subject: Re: VLF: Carrier on 3675.005 Hz
Yes
the signal is definitely making it to Amberg! This is a fine result of
mutual collaboration: Stefan DK7FC erecting the transmit facility and
posing the low frequency challenge, the DL0AO team (specifically Tom
DK1IS and Bernd DF9RB) laying out antennas in a quiet forest around
their club station and installing dedicated hardware, and myself trying
to tame 14 SpecLab instances without introducing too many errors.
The first indication of a 3675.005 Hz peak appeared already a couple
of days ago on the E-probe antenna, and is still shown in
the ultra-narrow 9.3 uHz window (waiting to be updated later tonight).
Since yesterday, antenna and GPS connections have been greatly
optimized, and the 31 uHz peak appeared early this morning after "only"
9 hours of averaging.
Best 73,
Markus (DF6NM)
-----Ursprüngliche Mitteilung-----
Von: DK7FC <[email protected]>
An: rsgb_lf_group <[email protected]>
Verschickt: Sa, 5. Aug 2017 11:17
Betreff: Re: VLF: Carrier on 3675.005 Hz
VLF,
After nearly 8 days the carrier is still on the air without an
interruption, despite occasional thunderstorms :-)
It looks like the SNR is suffering by summer QRN, as expected.
The stable carrier was good for doing local tests with my
Raspi+Octo-soundcard. The system is now completely configured including
system time setting via the GPS module. I recorded a few days from the
carrier, converted the data files into wav, reprocessed them in
SpecLab: The carrier is stable and on the expected frequency, so the
sample rate correction via vlfrx tools seems to work.
Forthermore i corrected some bugs in the circuit of my portable RX loop
preamp for VLF (must have been late in the night when i built it up a
few months ago). Now the noise is much lower. It looks promising! So it
is time for a portable VLF experiment in the far field, just to check
the system more seriously.
The crew of DL0AO has built up and optimised their VLF system to
receive the weak 3675.005 Hz carrier in abt 220 km distance. Looks like
there is something on their cardioidal spectrogram pointing to West,
http://df6nm.bplaced.net/dl0ao/VLFgrabber/vlfgrabber_dl0ao_test.htm
Something like 10 dB SNR in 31 uHz. That's not so bad!
I will run it for some more time until the trace is a bit longer. Then
in some days i like to start transmitting an EbNaut message on that
frequency which can be stacked until a decode appears. Markus has
developed a tool for windows to do the stacking, maybe it works in that
experiment... It will also be a test to see if i can decode the message
from my own recording using vlfrx tools, an important step to pass...
So far so good. What are YOUR projects you are currently working on,
LF/MF/VLF related?
73, Stefan
Am 28.07.2017 16:56, schrieb DK7FC:
Hi
VLF,
I'm back from LF for a while and built up my large VLF coil which was
used on 2970 Hz in the beginning of the year. Actually it is under
maintenance, one of the six stacks has to be replaced. It is already
dismantled but the new wire is not yet wound on the 250 mm diameter PVC
tube again.
So now the resonance is higher! I didn't know where it is and just
connected the coil and scanned the frequency downwards. Near 3685 Hz i
found a maximum of the antenna. Since the Q is not extremely high, i
decided to tune to 3675 Hz and added the usual 5 mHz offset, to stay
away from multiples of 1 Hz.
So, now since 14:40 UTC a carrier is running on 3675.005 Hz.
The antenna current is 170 mA. I estimate the ERP is just 3
uW!
I guess this is a first amateur radio transmission on the 82 km
band and that class of ERP (?).
Hopefully the coil will hold the 15.5 kV with just 5 stacks of
windings. It's inductance is 3.9 H in the moment!
I intend to run the carrier for at least a few days, depending on the
feedback.
Good luck for the VLF experts!
73, Stefan
PS: A 424 uHz RDF spectrogram is running at http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
(First pixel appears in 30 minutes)
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