Essais TX VLF DK7FC

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F4DTL
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Re: Essais 6,5 kHz DK7FC

Message par F4DTL » 02 octobre 2010, 16:13

Hello Stefan LF/VLF group,

Very nice copy in a quiet location in JN18IP. Distance is roughly 460 km.
I have a full record, almost 1 Gb, of the input.

Thank you Stefan.

73 Michel - F5WK

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Re: Essais 6,5 kHz DK7FC

Message par F4DTL » 02 octobre 2010, 17:54

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Re: Essais 6,5 kHz DK7FC

Message par F4DTL » 03 octobre 2010, 01:44

Wow!
Dear VLF,
This was very nice to read. So many messages and so many positive receptions. I am really impressed!

Many thanks to you all who have been active on this day, watching on 8,97 kHz, the Dreamers Band :-)

We have a new world record of the maximum distanced reception on VLF (by amateurs): SQ5BPF at a distance of 904 km with excellent S/N. Congratulations!! See attached picture.

Thanks to Markus/DF6NM for QSP to the reflector. Sorry to Wolf/DL4YHF that i was not QRV on 2m CW but there were problems to that time (see below). Thanks to SQ5BPF for the positive SMS ;-) Thanks to the US and canadian stations who tried to receive the signal. It becomes more and more probably since the S/N values are impressive here in EU.

Congratulations to all successful receiving stations, especially the new ones (on 8970 Hz) which are as far as i can see: Daniele Tincani, SQ5BPF, DD7PC, DF0WD, F1AFJ (683 km since my locator is/was JN49IS), F5WK (very impressive S/N 25 dB at 460km distance!), DL3ZID(463 km) :-)

Those S/Ns we have seen in this test seems to make even much more possible in future experiments. And the QRN will even go down in the coming months i hope.

My todays report:

It was raining in the early morning and i asked myselfe if it makes sense at all to go out of the bed. But i did and as i finished packing all the stuff in the car the rain stopped :-) Arriving on the hill there was everything wet and my copper ground plate was hidden at some meters into some buddles. So the earth losses were reasonably low!
After building up the wind was even strong enough and almost during the whole experiment the wind was strong and stable. The kite was in an angle of 60 deg and above. First i used the 3.6m^2 kite, later the wind was a little weaker and i changed to the 8.1m^2 kite. The antenna length was 200 m (about, maybe 220 m).
The first time i became QRV on 8970 Hz with the 200 m vertical after finding the correct tap on the coil which reduces the DC resistance by 100 Ohm.
Also the first time i measured the PA power by a true rms digital multimeter which has a mains adapter and can measure (U, I, P, cos phi). The average power (resistive power in W, not VA) is, to my surprise, just arround 300 W. Anyway i reached an antenna current of more than 1 A. The amperemeter was hanging on the right catch sometimes, just as it has to be ;-) So this goal is reached! :-) I have to change the measuring range now ;-)
Feeding 1 A in this antenna means just about 16 kV on the antenna and an ERP of 27 mW. The overall losses are now estimated to be 380 Ohm (180 for the coil). The antenna efficiency is now 0,0037 % :-). So, the 50 mW ERP level was not reached. I think this is due to the changed ratio of the winding turn numbers of the coil, so i have to reduce the primary turns in the same ratio (70%)...
300 W means that even 3 dB more should be possible with this generator but this will probably be the maximum ERP i can achieve, at least on a 200 m antenna ;-)
First there were some problems with the FET drivers (2x IR2110 for the H bridge) but after making a connection between ground/earth/soil and the heat sink it was no problem at all for the rest of the time. BTW: Still the first FETs in the PA(s)! During finding the problem i used my small class D PA with the 12V input and achieved 600 mA antenna current.
Actually i wanted to transmit "CU" on 8970 Hz but later i saw that the DFCW switch didn't work. So it was just a 40 minute carrier instead of a C, never mind ;-) Later i changed manually the DFCW step during telephoing to Markus/DF6NM ;-)
Suddenly the fuel of the generator was gone and i made a stupid mistake. It is a two-stike engine and needs some oil into the fuel, 2%. But instead putting the oil into the fuel i put it into the tank and later put the fuel in the tank too. This caused that the oil was in the engine and carburettor (100% not 2%) :-( Thus it was not possible to get the generator running again. More than 100x i tried to start it but no chance. During the tests to get it running again the kite was at a very high angle, about 70...80 deg and it was very stable for hours! No wind problems at all this time. Thus i started the small PA again and got the power from the car generator. The volatge was lower as it seems. This seems to be the reason for the... aah, i just got idea that it was the temperature rise of the car engine that heated the VFO and thus my last carrier dropped continously in frequency. The VFO was placed on the car, you know ;-)...
OK, after a longer carrier i stopped since there was no chance to get the generator running and so i finished my 7th experiment at 15°C and optimal wind and a nice saturday afternoon at low QRN :-/ But anyway it was a great success, isn't it? :-)
Sadly, there was no chance to transmit on 6470 Hz since the H bridge PA has to be used for this (ferrite core of small PA is already in saturation at 6470 Hz). Also a longer carrier would have been good on 8970 Hz during the time of the Florida's QRN minimum (sri Paul), but the 40 min carrier should be fine for long time integration tests. Maybe a surprise will come up by Paul? :-)
The CW tests were not done since the signal levels have been to weak at DF8ZR and most probably even on my grabber. But i have recorded an audio file and will try to bury the CW signal out of the noise in 40 km distance...

If the QRN is at least as low as today and i can manage to add a last 3 dB power it should be possible to cross the pond i can imagine. Furthermore i will try to arrange a 300 m vertical on the next experiment and will transmit on (arround) 5170 Hz, the 58 km band! ;-) Coming back with 300 m on 8970 Hz means again 3 dB more. It seems to have no end ;-) BTW: i have heared about special licences for kites up to 1500m above GND! ;-)
Another advantage in the next test will be a GPS tracked VFO signal, the GPS module is already ordered...

OK that's i have to report so far ;-)

Some photos of the experiment will appear on http://www.qrz.com/db/DK7FC

Again many thanks for all reports and screenshots and i hope you will take part of the next experiment, that will be in some weeks (maybe just 2 or 3). Maybe other experimenters will come up soon? Would be nice!

73, Stefan/DK7FC

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Re: Essais 6,5 kHz DK7FC

Message par F4DTL » 04 octobre 2010, 23:46

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Re: Essais TX VLF DK7FC

Message par F4DTL » 16 octobre 2010, 13:36

Dear VLF,

I have updated my website at http://www.qrz.com/db/DK7FC with some
photos and a short summary. If you are interested, take a look at it ;-)

73, Stefan/DK7FC

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Re: Essais TX VLF DK7FC

Message par F4DTL » 21 octobre 2010, 17:15

Dear VLF,

This weekend i plan to do my next kite experiment. I have got the permission for a kite ascent up to 300m above GND on my QTH in JN49IS36VH.

I will be QRV either on saturday or on sunday, depending on the wx. Attached you see the current wind forecast. For saturday the wind is not optimal, a little weak but it will be dry. On sunday the wind is quite strong and stable but there is probably some rain... I will have to see on friday evening if i can start on saturday or sunday and will announce that here.

If i will start on sunday, where the SAQ transmission takes place, this will be no problem since one can listen to SAQ and receive my transmission on an other computer based RX (e.g. SpecLab), so both can be done to the same time :-).

The starting time should be as early as possible. I have the permission at 6...16 UTC!

The program is to...

- rise the 200m vertical and transmit a long carrier (30 min) on 8970 Hz, after that a message in DFCW-600 and after that a message in DFCW-120, then a short CW test.
- transmit on 6470 Hz in DFCW-600 hoping to be copied at further stations (maybe M0BMU, SQ5BPF, OE3GHB, PA3FWM...?)
- if the wind will be optimal i will add another 100m and will try to transmit at 5170 Hz, 58 km band. This might be once again the lowest frequency an amateur has ever transmitted and reached the far field and above 1 Lambda, so each reception will be a WR for amateurs ;-) BTW, my grabber in Heidelberg is in < 1 Lambda ;-) The mode will be DFCW-600 as well.
- Then, coming back to 8970 Hz (maybe in the late afternoon) and transmit a looong carrier for long time integrations, maybe for a new ODX.
- reach 1,4 A at 8970 Hz, 1 A at 6470 and 5170 Hz
- be detected at 3 new stations and a new ODX ;-)
- use a GPS disciplined transmitter (trying SpecLab as the VFO and DFCW generator the first time)
- measure the R, 'C' of this 300m vertical on 137 kHz, preparing a new test there ;-) Since it is 55 % of a full size lambda/4 GP, 5 pF/m is not valid i assume
- be fascinated by the view of such an antenna which easily finds place in my car after the test ;-)

Until now i don't know who of the german LF group members would be possibly on the phone to make QSP to the reflector, just like Markus did it in the past. If there is a german member who likes to do that job, please send me a personal mail to exchange the phone numbers (Festnetz oder O2). Otherwise i have to play my game there alone and will see what happend in the evening ;-)

BTW, the generator is running again. It started to run again just as i have packed all my stuff in the car after the last experiment :-/ Never mind...

Have i forgotten something?

Please tell me if you think it is no good idea to transmit during the SAQ transmission or what is your favorite day, if both is possible here. I would prefer sunday, if the rain forecast changes to sunny :-)

73 and looking forward to the weekend :-)

Stefan/DK7FC

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Re: Essais TX VLF DK7FC

Message par F4DTL » 22 octobre 2010, 18:28

Dear VLF,

Its not an easy decision but i will start tomorrow, saturday 23. october. I want to start at 6 UTC but maybe it will be later due to the low wind. The wind might be to low in the early morning but maybe it is enough. In the afternoon and evening it will be very strong so optimal conds for EU. If it would be not enough i could think about trying again on sunday (much total effort) but it would be very pity to say i start on sunday and then, to much rain comes down!

Markus/DF6NM is currently in Israel and will receive there! :-)))

I have got and proven my 2nd GPS module and will transmit GPS locked!

In such a activity there is no chance to define an exact plan when i will transmit in which mode and frequency, just some rough ideas can be made, as done.

The Dreamers Band (8970 Hz) transmissions can be seen at http://www.iup.uni-heidelberg.de/schaef ... abber.html
The 46 km and 58 km band transmissions can be seen at http://www.iup.uni-heidelberg.de/schaef ... bber2.html

Some others have set up grabber pages as well. Please publish them here!

73 and good luck for the RX stations :-)

Stefan/DK7FC

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Re: Essais TX VLF DK7FC

Message par F4DTL » 25 octobre 2010, 01:40

L'antenne cerf volant de 3OOm de DK7FC pour les transmissions VLF du 23 octobre.

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Re: Essais TX VLF DK7FC

Message par F4DTL » 25 octobre 2010, 14:57

Dear VLF,

So, now after another very successful VLF experiment i want to summarise some informations and achieved results.

First i want to thank all those who did and tried to receive my VLF signals on up to 3 different VLF bands! Without so many RX stations, increasing and increasing numbers, it would not be worth to do that effort all the time, especially the 300m kite!
Thanks for so many RX reports! There are very interesting and different results from different stations. Here, we can learn a lot of VLF propagation and suitable RX systems, it seems.

Special thanks to Marco/DD7PC who was available on the phone to inform me and made QSP to the reflektor!

Most amazing seems to be the results of the 5170 Hz receptions of SQ5BPF and OE3GHB, with a very impressive S/N! Please, can we have a detailed RX antenna description and some wideband (0...24 kHz) screenshots? As far as i know both of these staions are using E field antennas!!

Congratulations to the successful receptions! As far as i know, in my 8th experiment there have been the following results(new= bold; new ODX=underlined; (distance/km)):

Dreamers Band / 33km / 8970Hz:
Daniele Tincany(707), DK7FC(40), M0BMU(657), DD7PC(53), DJ2LF(176), DJ8WX(461), DK6NI(165), DL3ZID(462), DL4YHF(264), Michael Oexner(72), EI8JK (1310!!!!!!!!!!!!!!!!!!!!!! :-) ), F1AFJ(683), IK1QFK(544), OE3GHB(594), PA3CPM(367), PA3FNY(360), SQ5BPF(904)

46km / 6470Hz:
DD7PC(53), DK7FC(40), IK1QFK(544), M0BMU(657), Micheal Oexner (72), OE3GHB(594), PA3CPM(367), PA3FNY(360), SQ5BPF(904!!!)

58km / 5170Hz:
DD7PC(53), DK7FC(40), OE3GHB(594), PA3FNY(360), SQ5BPF(904!!!)

There have been some stations without a successful reception. I think in most cases this is due to a non optimal RX antenna or to much QRM. But both cases can be optimised. QRM=> going out in the field (like i do ;-) ), insufficient effeciency=> optimising the RX antenna. In the case of W1VD, i assume neither the RX nor the QRM is the problem. Here, i/we have to find the best time for such a test to USA. And: It is nice that the ODX is increasing in "small" steps. That makes it very exciting, isn't it? :-)

The new DX record by amateurs on VLF is acquired by Tony/EI8JK, 1310 km. It is very interesting that he used a E/W orientated "earth antenna" to receive the signal! He already told me that he found some methods to strongly improve the S/N! Although the color scale of the capture is a little dark, it is an undoubtly reception. If it could be with even better S/N, as he means, there should be some chance to reach even more distance! We will see..

So, here my report and some data of the 8th experiment:
I arrived on the hill at 5 UTC. It was almost dark and the temp was below 0 °C. The moon enlighted the field, and the sun started to enlight the sky. There was no wind at all! As i finished building up the system, the sun came out, at 6 UTC. Still no wind but it came up slowly. At arround 8 UTC the kite was up and the wind increased to an optimal level without breaks. So i could transmit a long carrier (1 hour), GPS locked, at 8969.975 Hz. After that i had the idea to transmit a short mesage in DFCW-600: "GM- good morning" ;-) This was successfully received by 17 RX stations in 8 countries!
The kite was stable in an angle of about 70 deg an the average antenna current was about 900 mA, peaking 1 A, so 16 kV rms on the wire. Since the earth lossed seemed to be higher, a TX power of 550 W was necessary this time. This seems to be the limit of this generator but the coil/wire/PA will at least handle 2 kW, i assume! There was no noticable temp rise at the PAs heat sink during this 1 hour transmision! :-) So, the ERP was once again up to 27 mW.

Marco/DD7PC kept me informed about the traffic in the reflector, tnx.

After that it was possible to make QSY to 6470 Hz just by changing the transmit frequency (within SpecLab!) and the tap of the coil. It took maybe 2 minutes to become QRV there on 46 km, as can be seen on the captures. On 6470 Hz, the coils losses are 100 Ohm higher. The achieved antenna current was 900 mA. Since the wind was even stronger to that time, the average current was 900 mA as well, 20 kV rms on the wire. Thus the maximum ERP here was 11 mW.

Since the generator was running at full power it took very much fuel in a short time and i thought this could become a problem since i wanted to try a 300m vertical antenna at 5170 Hz as well. So i decided just to transmit a 40 min carrier for long time integrations and a "K", to have a trace that can be undoubtly identified as my transmission. During that time i rolled out the 100m kite antenna to switch it in series to the 200m antenna later (exciting experiment!). The wind increased even more during that time and so it took some time to become QRV there on the 58 km band.

I decided to exchange the kite to the smaller version (3.6m^2). This "small" kite took the whole kite line and the 300m wire until i pulled it down after the 5170 Hz test. But the angle of the antenna was lower, maybe 60 deg (sometimes 70 deg). First a applied my DDS VFO since the resonance can be easier found with the durning knob instead of a SpecLab slider. But this frequency seems to cause EMC problems in the VFO although it is driven by a battery and the output is fed into the PA by a fiber optic cable! Not so the PC! SpecLab generates the TX frequency and supports the audio output. I used a homemade fiber optic link (using the 5V of the USB as the power supply) working with a class A LED driver.
I found that 5170 Hz is not the resonance frequency of this antenna. Actually it is higher, at arround 5290 Hz! At 5290 Hz i got about 850 mA average antenna current! But i decided to stay at 5170 Hz since i wasn't sure about the QRM situation on other frequencies and most of the RX stations (including my grabber) are focused on this QRG, i assumed. With the variometer adjusting for minimum L i reached an average antenna current of 400 mA on 5170 Hz, so about 6 dB more ERP could have been possible with a suitable QRG or wire or coil! This means, the voltage on the wire was about 7 kV rms and the ERP just 2 mW (!)
Anyway, Gerhard/OE3GHB received the 5170 Hz signal with about 20 dB S/N in 594 km distance, just about 10 Lambda ;-) !! (and SQ5BPF at 10 dB).


We should think/ask about how this can be possible!! I do not think that it is just due to low QRM and a good antenna but due to the propagation as well!!???
I will repeat the 5170 Hz tests and will try to make the wire a little longer :-) 5170 Hz is critical for some RX locations since the local mains hum is already an issue there. But this is just a new challenge to take, isn't it? ;-)

Now, since i know that the resonance of the 300m wire is at 5290 Hz, i know where to make a 3rd (and last) tap on the coil to come back to 8970 Hz with a 300m vertical. This will increase the ERP by another 3...4 dB (reduced coill losses and a factor 2.25 in radiation resistance).

300m and 5170 Hz is my limit! I will not go lower, sorry ;-) Maybe the losses and be reduced and/or the power can be increased but here i will stop, at least with the kite antenna (not with the earth antenna) :-)

So, looking forward to the 9th experiment that will probably be in november 2010. Will you be receiving? :-)

Best 73, Stefan/DK7FC

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Re: Essais TX VLF DK7FC

Message par F4DTL » 25 octobre 2010, 15:03

La belle reception de Michel F5WK depuis le RC F6KBM de Cessons 77, Michel a utilisé cette fois une antenne fouet de 1,4 mètres avec son préampli était fixée sur un pied photo monté au maximum. Le dégagement n'avait rien d'exceptionnel, au contraire, avec la présence à une vingtaine de mètres d'un rideau d'arbres
entre 15 et 18 mètres. (source F5WK)

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