форум Радиолюбительского ДВ портала > Прием на длинных волнах
VLF, very low frequency, 3kHz to 30kHz
rw3adb:
--- Цитата: R6LDD от 16 Июнь 2016, 01:15:03 ---
--- Цитата: Сергей RA1ADF от 16 Июнь 2016, 00:56:55 ---Вот так на 37.778 кгц ТХ. Закон нарушил.
--- Конец цитаты ---
Ну,не считается. Передача была минуту-две? А вот ниже 9 кгц. для нас, имхо, лазейки есть:
http://www.minsvyaz.ru/ru/documents/3634/
Закон о радиосвязи.
1. При использовании радиочастот ниже 9 кГц не должны создаваться помехи радиослужбам, которым распределены полосы радиочастот выше 9 кГц.
2. При проведении научных исследований в полосах радиочастот ниже 9 кГц Администрация связи Российской Федерации обязана поставить в известность администрации связи иностранных государств о проведении таких исследований, для того чтобы были приняты все возможные меры для защиты этих исследований от вредных помех.
4. Полоса радиочастот 9-16 кГц может использоваться для научных исследований.
--- Конец цитаты ---
буржуи ровно тем и банкуют. у нас пока, кроме местечковых экпериментов на 8 кгц в опере- более не слыхал ни о каком сдв вообще
Сергей UB1APE:
Ух ты! Дык я запросто любую могу. У меня и дроссель есть 7,6 Генри величиной (и весом) с 100 -120 Ватный силовик намотанный проводом диаметром 0,5 мм. Правда слегка поврежденный, но межвиткового замыкания нет.
R1QBI:
--- Цитата: Сергей RA1ADF от 16 Июнь 2016, 08:11:29 ---Ух ты! Дык я запросто любую могу.
--- Конец цитаты ---
Вот и прекрасно.:) Осталось дело за биотуалетом.:) Под катуху.
rw3adb:
Ударник ULF Стефан вплотную освоил 2.9 кГц!
ULF: Key down signal on the 101 km band, still on the air
Hi all,
Since sunday 13 UTC i'm running a carrier on 2.970000000 kHz. The ERP is
100 nW. The antenna current is 30 mA.
The signal appears at up to 30 dB SNR in 424 uHz on my 3.5 km distant
remote grabber,
http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
I've done a successful test with a portable active E field receiver: abt
15 dB in 3.8 mHz in 4.5 km distance in a quiet location:
http://no.nonsense.ee/qth/map.html?qth=JN49IK66KU&from=JN49IK00WD
So 4.5 km is the new distance record on that band :-)
This was just for testing the receiver, which still needs some more
input signal get get it's full sensitivity.
The actual next goal is 50% of the far field border, i.e. ~ 8 km distance.
Paul, if you are reading this: It may be worth to try to integrate the
overall transmission time into one peak. I will continue to run the
carrier. So far, these 72 hours are not enough to get a peak i estimate.
But with one or two weeks integrated in one peak?? Maybe... :-)
The QRN is much lower relative to 8.27 kHz, so this may help.
There is some QSB on the 3.5 km path to my grabber. I've watched the
phase stability over that path: It is constant, as expected:
https://dl.dropboxusercontent.com/u/19882028/ULF/2970%20Hz%20RDF%20stabile%20Phase.jpg
Now my assumption is that the signal level drops when the forest is wet,
although it is a loop antenna! That also means that my RX sensitivity on
2.97 kHz is limited by the RX, not by the band noise. So the actual SNR
could be better...
A photo of the TX transformer/coil in it's final position:
https://dl.dropboxusercontent.com/u/19882028/ULF/20160623_234516.jpg
The 8 km distant ULF detection test is planned for this weekend. If it
works well, i'm doing a second test in EbNaut in the same location :-)
73, Stefan
rw3adb:
да, всё забываю занести интересное сюда.
20 июля 2016 Маркус такое письмо послал в РСГБ:
VLF: Mysterious Echo on NML LaMoure?
The signal from NML (LaMoure, North Dakota, 25.2 kHz) is showing the familiar ripple pattern of dual-path propagation: http://www.df6nm.darc.de/vlf/vlfgrabber.htm
Similar effects have been regularly observed on NWC (Australia, 19.8 kHz) and VTX1 (India, 16.3 kHz), due to superposition of short and long path components. The pitch of the ripples in the frequency domain is the inverse of the time delay, and thus proportional to the path difference.
The strange thing is that the pitch on NML is about 45 Hz, much wider than the others. This corresponds to a path difference of only 6.7 Mm. The direct great-circle range from LaMoure to Nuernberg is 7.4 Mm, thus the second component should have traveled around 14.1 Mm. Thus in this case, the long great-circle path (32.6 Mm) clearly has to be ruled out.
We also find that the pattern moves up slightly after our sunrise, indicating decreasing delay difference. This would imply that the delayed component seems to accelerate more during the progress of daylight than the direct component - quite the opposite of what is observed in the short-long path scenario.
So what is the physical mechanism of the echo? I really have no clue! A reflector on the North Pole?
I'm pretty sure that it is not a receiver artifact. As the strongest effect occurred around our sunrise (3 UT), I was tempted to speculate about "grey-line" propagation, picked up and guided by the terminator, which is currently not very far north of the Atlantic great circle path. But quite clearly the extra path length would be way too small, and we'd still have to assume some magic to explain most of the 22 ms delay.
Comparing ripple patterns simultaneously received at different locations could provide some insight. Even with relatively small receiver spacing (a few km between sites, e.g. the two receivers in Heidelberg), we might already observe slightly different phasing and thus shifted maxima. This could let us deduce the arrival angle of the late component. At larger RX spacing, the variation of time difference could be large enough to result in visibly different frequency pitch.
All the best,
Markus (DF6NM)
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