Hi ULF,
Here are the results of my post processing of my recording from the
last weekends experiment. The recording time was just 28 hours,
a 9.4 GB file.
The experiment took place in France, JN38OO27QJ
The distance to my transmit antenna is 140 km:
http://no.nonsense.ee/qth/map.html?qth=JN38OO27QJ&from=jn49ik00wd
The experiment was done on 2970 Hz, with an antenna current of 150...160
mA on my inv-L antenna. The ERP was in the range of 2.8
uW. Up to 17.8 kV was applied to the antenna wire and coil.
On the recording one can find a carrier taking 8 hours, a DFCW-10800
transmission (message 'F') and 4 EbNaut messages.
First, a spectrogram showing the complete recording, without filters
and blankers: https://dl.dropboxusercontent.com/u/19882028/ULF/ULF140km.jpg
The RX antenna is a single turn vertical loop having 40m circumference
hanging into trees. It is coupled to the soundcard input by a ferrite
transformer with 2 primary turns and 250 secondary secondary turns. On
the secondary side, the loop is resonated with low Q, about 40 nF (WIMA
FKP-1). Then there is a soundcard powered transistor preamp (ZTX690B)
with a RC low pass filter. So the QRN appears pronounced arround 3 kHz.
An analog band pass filter with low Q. But it provides more than 10 dB
of additional gain on that frequency.
https://dl.dropboxusercontent.com/u/19882028/ULF/424NMEA.jpg
Gives the best overview of the received signals. The carrier is very
clear with an SNR peaking > 20 dB in 424 uHz. The DFCW
message is partly hard to identify but the human-decoding experts will
confirm the character 'F'. Between the DFCW elements (1 hour long each)
i transmitted the same character 'F' in EbNaut (8K19A, 1ch, CRC21,
10s), i.e. 3 times. In the morning hours the last DFCW dash was very
strong and clear. The final part was an EbNaut message with 7
characters and a long symbol length. Apart from detecting the carrier
it was one of the main goals to detect this EbNaut message. 3 of 4
EbNaut messages decoded without a problem. The 7 characer message is so
strong that the signal becomes even visible in the 424 uHz spectrogram.
It was a noisy night for this time of the year! A noise background
difference of more than 20 dB between day and night.
Screenshots of the detection of the single character 'F':
https://dl.dropboxusercontent.com/u/19882028/ULF/2nd%20message.png
https://dl.dropboxusercontent.com/u/19882028/ULF/3rd%20message.png
Screenshot of the detection of the 7 character message 'F/DK7FC'
https://dl.dropboxusercontent.com/u/19882028/ULF/4th%20message.png
The signal could have been 10 dB weaker and would still decode easily!
More than 50 characters could have been transferred in the same time!
So there is MUCH space for further experiments in farer locations :-)
For comparison here's a screenshot of the transmission as received on
the tree grabber in 3.5 km distance.
https://dl.dropboxusercontent.com/u/19882028/ULF/ULF140km_Referenzbild%20_3.5kmQRB.jpg
These results are the first international (Germany -> France)
detection of an amateur generated signal on ULF (0.3...3 kHz) and a
first detection over a distance greater than 1 wavelength.
Last not least some images of the location and equipment (the loop is
hard to find, black wire...):
https://www.dropbox.com/sh/smoomlhlnv9ye9i/AADXXhxCbfrx6mWa1qt_ipwja?dl=0
73, Stefan
Am 19.01.2017 21:31, schrieb DK7FC:
VLF, ULF,
This weekend there will be some activity on VLF and ULF!
I'm running my next experiment on 2.97 kHz, my goal is to reach a 140
km distant location in France, JN38OO.
During that time (recording in F/ starting staurday arround 10 UTC) i'm
recording the spectrum from 0...12 kHz with a loop pointing to 30/210
deg. It is a very quiet location.
I invited DF6NM and DJ8WX to transmit on 8270 Hz. I guess that Paul,
SQ5BPF and RN3AUS as well as DF6NM and DK7FC are watching. Of course
everyone is invited to transmit and receive. Transmit stations should
announce their time/frequency here, to avoid any collisions. I am only
transmitting on 2970 Hz and i expect there will be no one else.
My transmission plan is:
Friday, 20th:
8...17 UTC carrier on 2970.005 Hz at 150 mA antenna current.
Saturday, 21th:
8...17 UTC carrier on 2970.005 Hz at 150 mA antenna current.
17 UTC...8 UTC: DFCW-10800 on 2970.005- 2970.000_ Hz (each dash takes
3h, each break takes 1h). Message: 'F'
Between each break (20...21, 0...1, 4...5 UTC): EbNaut, 8K19A, 10s,
CRC21, 1ch on 2970.000 Hz
Sunday, 22th:
8 UTC: End of the DFCW transmission
8UTC: EbNaut 8K19A, 32s, CRC16, 7ch on 2970.000 Hz
13:24:16 UTC: QRT.
More details soon...
73, Stefan
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