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1
Технический раздел / Аккумуляторы
« : 13 Август 2018, 19:31:56 »
Стефан тут нам пропанует Литий-Феррум-Полимеры для полевых сетапов.

https://www.robur-akku.de/


2
спросил в рсгб. не знаю, читаешь ли там или нет?

пишут кто-чего.
прислали малопонятный скрин, на котором якобы эта самая NAA под помехой еле видна.

Стефан написал, что это возможно DHO38, еще немцы предположили, что это возможно Корея.

No, NAA is visible at 24.0 kHz. Looks like South Korea.
See: https://groups.yahoo.com/neo/groups/VLF_Group/conversations/messages/25189

Peter, df3lp

Hello Genosse Roman,

NAA should be centered exactly at 24 kHz, like DHO38 is at 23.4 kHz. It
can have strong QSB and appears only a few hours per day. Here it
appears arround 4 UTC these days.
My grabber and all webpages do not work in the moment due to a webserver
problem which may be solved just next week...
These narrow traces are something else, NAA always looks like DHO, about
200 Hz wide.

73, Stefan

Stefan, Genosse, Roman:  For what it is worth, I can detect weak carrier lines above NAA near 24.2 kHz.

View from my analog DBM LF converter with e-probe in tree at 30ft, 50 ohm Bridge-T Q=1  diplexer driving  Mini Circuits ZFY-1-S Level 23 Mixer.  Isotemp OCXO LO at 3.0 MHz

https://www.dropbox.com/s/pklkpgsxushnznd/NAAETALL.JPG?dl=0

NAA is strong enough to hear it weakly with the antenna and diplexer disconnected, 30cm long 50 ohm cable for to the mixer picks up some 24 kHz energy that is weak but audible here...

73 Mike wa3tts


3
Опис


Спасибо за хороший отчет с картинками и кин, Саш!
Правильно сделал, что собрался с духом и потратил столько времени чобы все описать.
Таких экспериментов не очень много, так что будет полезно всем.

4
DP0GVN хорошо принимает.

да, принимают хорошо, а толку нету. связей не проводят. попросил их подтвердить проведеную еще 2013г в йт65 - в ответ тишина.
значит, все же вспышка подействовала... а сегодня верха молчат и проход в фт8 так себе. до дальних не добил не до кого. но фт8, это все же не вспр.-)

5
Влет ее не найти, вот 2 книги того-же автора:

спасибо, Александр!
да, оно вообщем не горит. но приникнуть было бы интерестно.

6
NAA
Цитировать
NAA Cutler, Maine, USA
44N3900 067W1700
biggest of all sites, 8000 mile ground net
Frequencies (kHz)
14.7
15.5 carrier visible with Spectran
18.6
22.3
22.35
24.0
25.3
25.82


Не попадает.

ну, как не попадает7 24.0
возможны же и ошибки частоты.
а по уму надо в рсгб или на радиосканере спрашивать.

UPD - спросил пока в рсгб.

7
Александр, к тебе вопрос, как к библиотекарю нашему заслуженному:

видал тут на днях где-то по аукционам книжку - История QRP в США 1924-1960
если вдруг попадется в эл виде - пришпиль к нам сюда.


8
Интересный буклет от G3XBM.

да, забавно. спасибо.

9
Солнце "тихое", днем ничего интересного. 

завтра бахнет. там вон пятнышко снова вернулось.

11
Результаты Стефана:

ULF,

With some delay here (attachment) are the spectrograms showing the carrier transmissions in 424 uHz FFT bin width. I would say it is 'O copy' and it clearly looks like there is some room for even longer waves to try :-)

I already checked what Wikipedia tells about SLF, https://en.wikipedia.org/wiki/Super_low_frequency

73, Stefan


Am 06.08.2018 16:19, schrieb DK7FC:

    Свернуть
    Hi ULF,

    On Sunday, 5th 2018 i successfully crossed the far field border on 2470 Hz for the first time. That's the 121 km band. Later i even crossed it on 1970 Hz, the 152 km band. These are two new records of the lowest frequency signals generated by amateurs and received in the far field. The distance between RX and TX was 55.6 km . The far field for 2470 Hz starts at 19.4 km distance. For 1970 Hz it starts at 24.3 km distance. The RX antenna and the TX antennas were loops!

    By running about 100 W (PA DC input) i managed to get 910 mA antenna current on 2470 Hz into the earth loop in JN39WI. Here i transmitted a plain carrier from 06:13...07:15 UTC.
    Later i QSYed to 1970 Hz and here i got 910 mA as well. The 1970 Hz transmission took place from 07:19...08:21 UTC.

    Despite beeing in the middle of a large forest there was good internet connectivity and so i was able so watch my own grabber window showing the band activity on 2470 Hz in a spectrogram of 424 uHz FFT bin width, which is very wide for that frequency range! The spectrogram uses a Hann window and the FFT window time is about 40 minutes, so it took some time until a peak builts up. But already after 20 minutes i saw that something happens! After 40 minutes the carrier transmission reached an SNR of about 20 dB! It was a relatively quiet morning for early August.
    All the VLF stream data is stored into a ~ 12 day covering buffer so i have the chance to optimise the filter settings and antenna mixing in a postprocessing to achieve the best SNR from the system.

    For the 1970 Hz transmission there was no spectrogram available but since i had internet access and a Linux notebook available, i processed the VLF stream data (via SSH remote access to the storage PC) during the transmission and followed the peak's SNR building up!

    It clearly looks like this antenna outperforms my large inverted L in 30 m above the ground, at least into the ULF range! This opens up a new room for experimentation on the way down to DC! :-) Now i need to get rid of these output transformers since they will become problematic for wide-band experimentation on ULF / SLF.

    Now, attached you can find two images showing spectrum peaks from the two bands, out of the 55.6 km distance. The complete transmission time is here integrated in one peak. Since the carrier S/N can also be calculated from decoding a '*' message in EbNaut, i also show the results for such calculation along with the whole postprocessing chain.

    Spectrograms will be produced as well, but this will take a few hours here...

    73, Stefan

12
Свободное общение / Re: Дипломы
« : 04 Август 2018, 14:58:26 »
Поздравляю! Мест под доску присмотрел уже?:)

при такой ее стоимости, боюсь, она так и останется не полученной.

13
Свободное общение / Re: Дипломы
« : 30 Июль 2018, 13:23:16 »
Итак, сварилась e-Europe!
20 лет понадобилось чтобы собрать ее в MIX - ssb, fm, JT65, RTTY и всего ОДИН год чтобы собрать ее в FT8!
Диплом, конечно, получить пока не судьба - 12 баксов членство и стольник сама доска, но все равно похвастаюсь, приятное событие!


14
Новые результаты продолжающихся экспериментов Стефана:

As a next result from today's experiment, here is a spectrum peak of the
2970.005 Hz transmission. I reached 20 dB SNR in 180 uHz! This far more
than expected, in July anyway.
It is the first ULF transmission (by amateurs) from an earth electrode
TX antenna, detected in the far field.
Spectrograms will be produced soon...

73, Stefan


Am 29.07.2018 16:01, schrieb DK7FC:

    Свернуть
     Hello Roman, VLF,

     I transmitted pure carriers each time. It was just a first test.

     Today i've done a second experiment, this time using a 900m long wire!
     So the wire should have about 125 Ohm DC resistance. I measured 220 mA
     DC at 38.4 V, so the overall loss is 175 Ohm. Very interesting; the
     ground loss resistance stays at 50 Ohm although the distance between
     the electrodes has doubled!
     If i would use the 0.75 mm loudspeaker cable then i can reduce the
     losses by 100 Ohm which is more than 50 %, so i will gain 3 dB at the
     same output power! Then with a switch mode PA having nearly 100%
     efficiency i may gain 2 dB more (mmy lonear mode PA was not well
     matched today and quite warm). So maybe i can reach 1 A antenna
     current with just 75 watts??!!!
     Today i tuned to 550 mA antenna current again, at 8270 Hz. With the
     scope, i measured the phas, it was more inductive than yesterday. I
     actually found a 1 uF MKP-10 cap in my car and switched it in series
     to the antenna. This improved the phase slightly. Then i also found a
     low pass filter for 137 kHz, the pypical pi configuration, i.e. it
     acts as 4*22 nF in parallel here on this frequency. Switching this in
     series leads to a low current, so the C is to small. So for the next
     experiment i'm preraring a switchable C network (47n, 100n, 220n,
     470n, 1u, 2.2u, 4.7u). It will be even more necessary when i lower the
     wire resistance (higher Q).
     Well, today the QRN was much lower, especially for the 2970.005 Hz
     transmission period. Yesterday this was totally buried in the noise on
     my RX on the tree. But today! I transmitted another 90 minutes with
     much lower QRN background. I already have a clear spectrum peak but i
     like to try to improve it a bit more before presenting it here.
     Todays carrier transmissions:
     8270.000 Hz : 08:12...09:33 UTC
     2970.005 Hz : 09:42...11:15 UTC

     Sorry for the confusing email ;-)

     73, Stefan

-обращаю внимание, что до меня в рассылке его письмо не дошло! это уже ответ его самого на собственное сообщение.
так что будьте бдительны и если я что-то не выложил к нам - не стесняйтесь, выложите сами.

15
Предварительные результаты эксперимента Стефана.

Hi Roman,

Here are two spectrum peaks from 8270 Hz and 5170 Hz. I integrated the
complete transmission time into one bin. I also produced a wav file from
the recorded data (already resampled, mixed, filtered, blanked) and
postprocess this into SpecLab now, so we get a usual spectrogram
demonstrating that there was no trace before and after the transmission
on that frequency. The file starts 2 hours earlier and ends 2 hours later...
More tomorrow...

73, Stefan

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