Essais TX VLF DK7FC

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F4DTL
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Inscription : 10 mars 2008, 23:07
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Re: Essais TX VLF DK7FC

Message par F4DTL » 03 décembre 2010, 19:34

Dear VLF/LF group,

I will do my 9th VLF experiment tomorrow, saturday 4th December. The permission for a 300m vertical antenna is available! The wind forecast changed again and tomorrow is a very suitable day with stable wind and some sun. Anyway the temperature is about -6 °C. The forecast says that the wind will come up arround 9 UTC and it was shown that the 24h forecast is very accurate to the truth. Thus i plan to start transmitting arround 9 UTC. This may be unfavourable for a TA contact but it just makes no sense before sunrise here without wind. So we need a even greater wonder ;-)

My planned program (if all works well) is:
-Trying to use the 300m vertical on 8970 Hz. At 550W this may radiate up to 100 mW ERP!
-Transmitting a long carrier (about 40 minutes) and after that a short message in DFCW-600 on 8970.00000 Hz (50 mHz DFCW-shift)
-Transmitting a CW on 8970 message for a local test (recording in 4.7 and 17 km distance)
-Maybe transmitting a short message in DFCW-120 on 8970 Hz
-Transmitting DFCW-600 on 6470 Hz. I have to use the 200m antenna for this.
-Transmitting DFCW-600 on 5170 Hz. Since the coil is improved now i can manage to feed more power in the system. The last time it was 150W. Maybe i can reach the full 550 W this time.
-Building up the 137 kHz system during the VLF transmissions and doing some resonating tests with the 200m and 300m antenna.
-Transmitting CW (137.7) and DFCW-4 (137.7) and DFCW-60 (137.777 or 136.320, after talking to Markus or the other QSP partner).
-Maybe coming back to 8970 just befor sunset
-Trying to reach as most stations as possible.
-Trying to make a new distance record, e.g. 4X1RF on 8970 Hz in 2873 km and/or EI8JK on 6470 Hz in 1310 km.
-all i have forgotten

The signals are tracked by a GPS module and are transmitted by using DL4YHFs SpecLab! The accuracy is about 10 ppb.

You can follow the activity on many grabbers. Mine is in 40.00 km distance and is the nearest one. As usual, 8970 Hz can be watched at http://www.iup.uni-heidelberg.de/schaef ... abber.html , 6470 Hz and 5170 Hz at http://www.iup.uni-heidelberg.de/schaef ... bber2.html (the VLF-PC has had a power supply failure tonight. This has been exchanged today, so some windows (especially 6000 and 60000)) have lost some data. I hope it works now...
The 4X1RF grabber which is one of my goals is available at http://qsl.net/4x1rf/vlf/vlfgrabber.htm. There are several other grabbers that have and will be announced here.

All reports are very much appreciated!

Wish you fun and low noise :-)

Best 73, Stefan/DK7FC

F4DTL
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Re: Essais TX VLF DK7FC

Message par F4DTL » 04 décembre 2010, 17:14

Reception de DK7FC en portable sous la neige de Soignolles JN18IP, l'antenne est une boucle monospire fermée de 1m de diametre en cuivre recuit de 14mm de diametre.Le preampli faible bluit avec OP27 recupere les signaux via un tore monté en transfo de courant. Le recepteur est Spectrum Lab avec une configuration speciale de DF6NM avec une fenetre spectrale de 4 milli Hz pour ces essais amateurs.

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F4DTL
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Re: Essais TX VLF DK7FC

Message par F4DTL » 05 décembre 2010, 22:21

Hello Nicolas,

Congratulations to your very successful reception! Our distance is 453 km and this is one of the most impressing captures out of such a distance! I have never seen such a clearly reception at all. More than 30 dB SNR is a kind of new record too, almost unbelivable.

Thank you for your effort to build this antenna and to go out in the field in the cold snow. That makes me glad, to motivate people in the world to do such things :-) You can imagine that i can imagine what it means to be out there so long ;-)

I will write my detailed report tomorrow and be pleased to add you to the list of my successful VLF receptions :-)

Best 73, Stefan/DK7FC

F4DTL
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Re: Essais TX VLF DK7FC

Message par F4DTL » 07 décembre 2010, 19:11

Dear VLF/LF group,

After a very exciting and stressing VLF experiment i am back in the civilisation and am relaxed again. It was a very hard fight with kite in the dark cold until i have pulled it down after one hour!

A new distance record by amateurs on VLF was reached, 2873 km distance in DFCW-600 with a good SNR by 4X1RF on 8970 Hz and even fragments on 6470 Hz. Chris recorded the signal as a wav file so we can re-process the experiment in a even smaller FFT to at least extract a dash with better SNR. Congratulations!!! :-)

Many thanks to all the many receiving stations all over the world! That makes me glad to see the effort, people are doing to receive my weak signal (e.g. F4DTL). The receiving stations are an important part of this experiment! Not only new stations and/or distance records are fascinating but each station, no matter what the distance is! There have been 23 stations in 9 countries and 2 continents who successfully managed to receive the signals, partly on all the 3 VLF bands where i can transmit.

Special congratulations to 4X1RF, G4WGT, G3XBM, OK2BVG, G4AYT, F4DTL and ON7YD for the first successful reception on VLF. OK2BVG is the first contact between Germany and Czech Republic, ON7YD is the first contact between Germany and Belgium, 4X1RF the first contact between Germany and Israel (that counts to Asia if i am correctly informed). Attached you find a list of the successful receptions just of this 9th experiment. The overall receptions of my kite experiments and a geographic card will appear on my QRZ.com page in a few days.

Lets hope the activity, not only mine, can be increased even more by the upcoming stations with fixed antennas! It is worth to try it, even if much slower modes are necessary.

Now my report about the 9th experiment:

The wind forecast said that the wind will start to come up arround 9 UTC and that was true! So i arrived about 8 UTC on the hill. The temperature was about -6 °C and this didn't change during the day. But the sun came out and it was, once again, a wonderful day in the field. I have had 2.5 liters hot tea and enough to drink and fuel for the generator to stand a 10 hours activity out there. The wind was at excellent strength and stable. Once i lifted the kite it was up in the sky until i pulled it down! No QSB ;-)
After lifting up the first 200m i got the idea to start at 6470 Hz since i cannot resonate a 300m wire on this frequency, just 200m. Unfortunately some RX stations missed my 6470 Hz due to that change in schedule. (Hint: You can run all the 3 SpecLab instance to the same time, just by 3x double clicking the SpecLab symbol and load each of the 3 usr files into one instance! This takes some more CPU power but it is no problem. So you cannot miss anything. Its like having 3 TVs for each of the 3 programs ;-). )
Since the whole hill was covered by dry white snow, i haven't found my buried copper rod into the earth and so i had just the copper plate and one /p earth rod. But the sun shined on the copper plate and seemed to melt some of the snow under the plate, so the contact was not to bad. On 6470 Hz i managed to get an average antenna current of 800 mA , equal to up to 9 mW ERP and 18 kV rms on the antenna wire.

After that, the transmission on 8970 Hz followed. I have had several mobile phone contacts to DF9PW and top DF6NM but suddenly i got the message of the positive reception in Israel and a call from 4X1RF. This was very pleasing and exciting :-)
To my surprise my signal was visible in QRSS-3 at DF6NM but unfortunately i haven't had a suitable RX on 137 kHz available to this time. In the next experiment i will be better prepared on receiving LF (and HF, for some crossband contacts) and will try to make the first xband QSO on 9/137 kHz DFCW-3/CW to DF6NM.

After preparing the loading coil and making a tap at 190 mH (RDC=180 Ohm, which is rather worse) i easily found the resonance at 8970 Hz on the 300m vertical antenna which was very stable at a high angle (> 60 deg) for the whole transmission! Here the achieved antenna current was up to 1 A (950 mA average) so i reached an ERP of 58 mW and the voltage was just 10 kV rms (about LF conditions)!

During the transmission of "CU" in DFCW-600 i got a visit of a very kind man who wanted to take some photos of the great nature there. Of course he saw my high kite and asked what i am doing. Since he was a CB radio man in former times and works in the electric sector, he predominantly understood what i am doing and was impressed by the currently achieved world record and the whole setup and the technical data (such as Lambda=33km). So he took some nice photos and even wrote a report out of the view of a non VLF radio amateur which is really interesting to read. Here, some pictures are published as well. See: http://mkorbit.de/2010/12/05/weltrekord ... welle-vlf/ (in Geran language) If you want, just leave a comment there, he would be pleased by that i assume ;-)

Aftter a longer carrier and the message "CU" i moved to 5170 Hz. Changing the wire to the other tap (550 mH) was a little dangerous since the air was very dry and the wind seemed to carry charged particles that caused a static voltage on the wire. I got sparks of about 10...15 mm and since the C is about 1.65 nF there was a reasonable high energy on the wire. So i have to earth the antenna by a second cable befor removing the main wire. Anyway, QSY to 5170 Hz took about 2 minutes. After increasing the number of turns on the loading coil by about 12 i got some more antenna current on 5170 Hz, i.e. about 530 mA. In the last experiment it was just 400 mA but i am still not in resonance. So it should be possible to get 800 mA there as well. So, my ERP on 5170 Hz was about 5 mW and the voltage about 9 kV rms.

During the 5170 Hz transmission i prepared the LF/137 kHz equipment but i already gets dark slowly. So i haven't had much time on LF. Just a test to find the resonance and transmit some dashes that seemed to appear on the UA4WPF grabber in 3009 km :-) Although i was playing with a 100W soldering iron there on the hill it was not possible to make a suitable tap on the correct place. Also, there was a resonance but not 50 Ohms so it wasn't possible to use the class E PA but only a class D PA with very low power. Next time i will be better prepared and will do a experiment just on LF! :-)

After coming home in the dark i not even put the things out of my car but immediately fell in my bed ;-)

This was the 9th experiment and it was very exciting, funny, and successful. No problems, nothing missed, good WX, a nice record and still some challenges left :-)

I hope to CU in the next experiment, probably in January 2011! :-)

Best 73, Stefan/DK7FC

F4DTL
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Inscription : 10 mars 2008, 23:07
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Re: Essais TX VLF DK7FC

Message par F4DTL » 07 décembre 2010, 19:18

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