Hello Stefan,
congrats with the effort and the results.
I really must try to participate in the next test (although the distance between us in meanwhile peanuts).
You are giving a new meaning to the saying "the sky is the limit".
About the locator JN49IS36VH: if I got it right this is a 12m by 19m rectangle, only a small part of the antenna will fit in this rectangle !
73, Rik ON7YD
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
PS: I attach the updated VLF reception list of my experiments. Please let me know if you are missed or so.
