Форум радиолюбителей ДВ
Новости LF/VLF/ULF/SLF/ELF => VLF (ОНЧ — очень низкие частоты) диапазон с частотами от 3 до 30 кГц => Тема начата: rw3adb от 23 Ноябрь 2019, 23:55:49
-
Splendid work, Stefan! Thanks for the details of what must have been the first
amateur VLF message across the globe.
It seems the VLF TX on this end is behaving itself again, thanks to
your guidance. It was good to have some company from Riccardo on Paul's
spectrograms. A bit of tinkering is still needed here before EbNaut can
be attempted again.
73
Joe VO1NA
On Tue, 12 Nov 2019, DK7FC wrote:
Свернуть
Hi Joe,
Yes, the carrier transmissions were done to get an impression if and when the
path is stable and if this is reproducable over a few days. I transmitted
carriers for a few hours and later i tried to decode EbNaut '*' messages with
different start times and symbol lengths.
The results were plotted in an Excel sheet (attached) and we found that, when
stacking 4 days, that a 3 hour long transmission starting at 17.55 UTC would
give the best SNR of about 12.5 dB. One week later, the situation would be
different since the path is very dynamic and the sunrise/sunset times are
changing permanently. It looks a bit weird but in the end we managed to
decode a 1 char, a 2 char and a 3 character EbNaut message.
The antenna current was 1.2 A. I had some PA problems, EMC and so on. The
antenna should have managed 3 dB more signal.
Meanwhile the special licence for that band expired.
73, Stefan
-
Маркус пишет, что принимал Джо не плохо на 8 КГц на днях...
[rsgb-lf-group] VO1NA 8270 Hz
Когда: 2 января в 14:37
Hi Joe, LF,
continuing this thread, here is the data from DL0AO for December 2021. The carrier has been very well visible in our spectrograms.
Happy New Year to all in the group!
73, Markus
Ну и ответ самого Джо:
====================================
Thank-you once again, Markus. The carrier is also very clear in your 47.1 uHz instance, Stefan's VLF spectrogram and Paul's Todmorden RX site. The IQ
data shows the diurnal peaks and their first overtones in the FT (attached). The 2 negative and one positive peak in the imaginary (blue)
component have me curious!
Autumn has changed the aerial impedance -- the current was peaked by
increasing the tuning inductance slightly. Then the back yard thawed during a brief heat wave. The current was peaked this time by putting 1uF in the line to the shed. This is more convenient than going to the shed
to play with the tuning coils.
The tuning was relatively high and stable during the summer. The winter fluctuations are being monitored with a view to automating the tuning,
ideally using the clever ideas of the 'Automatic Tuner' 2000 you posted last year.
In the mean time, the plase is monitored by a scope with the ne07m going to Channel A and Channel B connected to 1 metre of wire tacked
to the shack ceiling. The phase is taken as the distance between the negative to positive transition of the neo7m clock and the peak of the
sense antenna signal a 75cm wire with 0 phase corresponding to peak aerial current.
Work is ongoing to make a recording phase monitor. An LM324 op amp has done well as a voltage follower for the sense antenna but poorly as a
zero crossing detector for the ne07m: it puts out a trapeziodal wave for some bewildering reason.
73's Joe VO1NA
Маркус прислал тхт с цифирками - прилагаю.
Джо прислал картинку.
-
С помощью какой программы ведёт наблюдение Маркус?
-
С помощью какой программы ведёт наблюдение Маркус?
EbNaut вроде.
-
Наверное. А попроще нет ничего?
-
Наверное. А попроще нет ничего?
Увы.
Они там пробили расстояние между Стефаном и Малом G3KEV - что-то ~850 км... Передавали несущую в щрсс-6000.
Но самые ДХ только в Ебнаут возможны.