Dear LF/VLF group and further VLF watchers :-)
After another very successful, exciting and fascinating /p VLF
experiment i want, as usual, thank all the many (>=24) receiving
stations who took the time to arrange a suitable antenna/receiver, PC
and to watch the experiment and take some interesting captures. The
transmissions took place on 2 VLF bands, 33km (8970 Hz) and 58km (5170
Hz).
So, thanks to TF3HZ, SQ5BPF, G4WGT, G3KEV, Daniele
Tincani, G3WCD, G3XDV,M0BMU, G3XBM, OK2BVG, OE3GHB,
G4AYT, IK1QFK, DL3ZID, F4DTL, OE5ODL, PA3CPM, PA3FNY, DL4YHF, DF6NM,
DJ2LF, DD7PC (bold = 1st positive reception on VLF).
Special thanks to Halldor/TF3HZ who wasn't member of this group
before but set up a very sensitive VLF receiver and even a most
intersting
grabber just by my email request. This is the first VLF detection
between DL and TF. My signal appeared at up to 15 dB SNR in 4.5 mHz in 2404
km. This helps a bit to get some imagination how far a
transatlantic detection is away.
Sorry to those who tried without success this time, like 4X1RF. The
next experiment will come soon, maybe in about one month.
Now, as usual, a looong report about last sunday:
The alarm clock ringed at 5:30 local time (4:30 UTC). The equipment was
already put into the car before. I arrived in the dark on the hill at
5:45 UTC and had to use my head lamp to build up the TX system. I am
getting more and more relaxed and routined in building up the system.
The wind was strong with some even stronger flurrys (like announced in
the forecast) so i decited to use the 3.6 m^2 kite. It was a
relatively warm day (compared to the 9th exp) at about 5 to 7 °C.
After rising the kite to 200m i started to transmit on 8970 Hz while
rolling out the second 100m long part since i didn't want to miss any
minute in the early morning. A capture of my total 8970 Hz activity can
be seen at
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/DFCW-600_DK7FC_10thEXP.jpg
Unfortunately my soundcard wasn't accurately locked to GPS within
SpecLab as it seems. Thus the signal looks fuzzy. Anyway there was good
copy on most receiving stations. Maybe this is caused by a high local E
field strength influencing the antenna but actually there was no
difference to the setup of the 9th experiment. I will work this out!
So the transmission started at 6:50 UTC. After getting the full
300m the signal became 15 dB stronger on my grabber ( i didn't get
exact resonance with the 200m part). Since it was wet i got an average antenna
current
of 1 A and peaks of 1.2 A at 8970 Hz, resulting in up to 84 mW
ERP and 13 kV rms on the wire.
The day before i bought a sledge hammer and hammered 2 long massive
steel earth rods into the soil. Since the soil was wet below the copper
plate and due to the rods it was possible to reduce the earth losses to
about 65 Ohms!! So the antenna efficiency was up to 0.013 % which
is very high :-) But unfortunately the generator seems to become
weaker and weaker. The average applied power was just about 250W.
Actually
it should be about 600W :-( So, another part to improve or to
replace. Thinking positive, this means i can improve my signal by at
least 3 dB if i get the generator running or 9 dB if i choose a 2 kW
type.
After transmitting a constant carrier at 8970 Hz for 80 minutes i
transmitted DFCW-600, for better ID at the various receivers. The
message was "FB-fine business", just for fun... After that i
did the first LF/VLF xband QSO in DFCW-3 with Markus/DF6NM over a
distance of 179 km! There was no problem to copy our signals in the
first attempt :-) This was very pleasing. Captures of this QSO can be
seen here:
http://dl.dropbox.com/u/19882028/DFCW3_QSO_DK7FC_DF6NM_9-137kHz.rar
Although solid copy of DF6NM was possible, the SNR was much lower than
expected. It is at least 15 dB lower than during driving on the highway
near HV transmission lines, even when the generator and so the netbooks
power supply is off! There was no improvement/change when the 300m wire
was disconnected or grounded. So i have to work on this too...
To my surprise i got informations (by mobile phone) that some other
stations seem to see me in DFCW-3 (like OK2BVG). So i will plan much
more QSOs in the next experiment.
Since the generator would have problems to stabilize the driving speed
when doing a DFCW-3 or CW transmission, i added such a tiny capacitor
of 60000 uF / 350V which averaged the load pretty good! This even means
that the TX power in CW or 3 is even higher than in DFCW-600!! When
switching on the PA after recharging the capacitors i got up to 1.7
A for a short while :-) A definite goal in this year is to get 2 A
antenna current. This may be the limit of this coil regarding power
dissipation and voltage stress (abt 30 kV rms).
After the QSO to DF6NM i did some CW transmissions. I did a recording
of the audio stream in a 30 GB wav file that is analysed in the moment.
Maybe this CW signal is audible in 40.0 km distance. I will report on
this later. It was funny to have a CW sidetone on 700 Hz and on 8970 Hz
together :-)
During the CW transmission the photographer of the last experiment
visited me again, taking a friend (also a photographer) there too.
There have been about 15...20 visitors on the hill asking interested
what i am doing :-) They both wrote a short article with some photos,
see http://mkorbit.de/2011/02/08/signalubertragung-auf-langstwelle-vlf/
and http://peweb.de/2011/02/06/dk7fc-signalubertragung-auf-einer-langstwelle-vlf/
After the CW message i moved to 5170 Hz, transmitting a long carrier
while talking to visitors there. Later i added a "K" in DFCW-600 just
for ID. During that time there was no QSP to the reflector except some
SMS to SQ5BPF and 4X1RF (thanks for the entertainment). BTW thanks to
DF6NM for QSP to the reflector during the first hours. I will now
actually try to improve my /m antenna for the 30m band to give better
chances for skeds.
Due to the low feedback i thought there is not much interest in 5170
Hz although i like that band very much. The coil is still not
resonated but anyway i reached the limit of the generator, resulting in
about 800 mA antenna current, so up to 12 mW ERP on the 58
km band. BTW Markus/DF6NM is planning to visit me in one of the
next experiments carrying his coil there. We will couple them and try
to transmit on 4 and 3 kHz! I estimate we can reach about 6 mW ERP at 3
kHz :-).
Another story: Jacek/SQ5BPF asked me via SMS to make QSY by 10 Hz for 1
minute. So i switched to 5180 Hz for a while. After that i pressed the
DEL button in the text field of SpecLab where the TX frequency is
typed. I did this during transmitting. I wanted to replace the 8 by a 7
to come back to 5170 Hz. Suddenly i heared a short BEEP! at a much
lower frequency and realized quickly that i obviously transmitted on
510 Hz :-) But all this is no problem for the PA :-)
Later i came back to 8970 Hz. No transmission on 6470 since i have to
reduce the antenna to 200m for this and wasn't sure if a QSO to HE3OM
on 137 was possible... In the late afternoon the WX was fine, sunny,
warm but the wind slightly decreased and the antenna began to sag.
Since i didn't want to go home and loose this valuable TX time i
actually changed the kite and used the 8.1m^2 kite later. This one is
much more stable in the wind and at a high angle! So my average ERP
must have been a bit higher in the late afternoon. This gave
Roger/G3XBM the chance to copy me later. I haven't known all that on
the hill ;-)
Some DFCW-10 messages and DFCW-60
(http://dl.dropbox.com/u/19882028/dk7fc_60_110206_1652.jpg)
was the
last transmission of my 10th VLF experiment.
Ending arround 17 UTC and slowly building up the setup needs to use the
head lamp again! It takes more than a hour to build up and down the
system. So i spend the whole day on the hill and had a lot of fun there.
I'm once again happy about so many detections by stations across
EU/UK/Iceland and hope you'll be there in the next experiment, would be
pleased about that :-)
A list of successful receptions of my 10th experiment with locator and
distance can be found here:
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/VLF_DX_DK7FC_10th.png
A complete list of positive receptions of all my experiments can be
found here:
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/VLF_DX_DK7FC_all.png
A google earth map of these stations can be found here:
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/VLF_DX_DK7FC_map_all_above_200km.png
A google earth map of rather local stations can be found here:
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/VLF_DX_DK7FC_map_local.png
Last not least a map that shows the presence of the sun during my
attempt to leave a trace at Laurence's / KL7UK VLF grabber in the early
morning:
http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/map_KL7UK_DK7FC_10th_morning_sun.png
So, see you in the 11th experiment. :-)
Vy 73, Stefan/DK7FC
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