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Новости LF/VLF/ULF/SLF/ELF => VLF (ОНЧ — очень низкие частоты) диапазон с частотами от 3 до 30 кГц => Тема начата: rw3adb от 23 Август 2018, 16:56:10
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Стефан провел новый эксперимент ни 17.47 кГц.
Результты обнадеживают - сигнал принят с большим уровнем на расстоянии 881 км! Возвожна связь и передача сообщений в обычном режиме QRSS-60.
VLF: New experiments on 17.47 kHz planned...
Когда: 20 авг. в 17:29
Hi VLF,
For this week, i'm planning to start with new experiments on 17.47 kHz,
where i have a (renewed) special permission to transmit.
So far the best results were a prooved carrier detection as well as a 1
character EbNaut decode by Edgar from Tasmania (VK7).
The first goal will be to determine the best time (start time and
length) on the path for this season. We have a usable path for about 2
months centered on our autun/spring time (21st SEP).
The Signal will be exported by SpecLab to simple txt files containing
the FFT data. This allows stacking, which will be required to get some
S/N at all. A reasonable stable path is essential during the
transmission time. All this will be determined by running some carrier
transmissions, a few hours per day, starting about 16 UTC.
When knowing the time to try we will attempt to transfer a 2 character
message and then even longer messages. 5 characters would be realistic i
think, with some luck and good propagation and low QRN on the RX site...
More soon.
73, Stefan
VLF: New experiments on 17.47 kHz planned...
Когда: 23 авг. в 10:41
Thanks Paul.
That would be good for the traditional QRSS-60 over our distance. Not
bad at all for such a noisy summer!
73, Stefan
Am 23.08.2018 06:43, schrieb Paul Nicholson:
Свернуть
> Reports welcome :-)
A great signal in Todmorden, 881km.
http://abelian.org/vlf/tmp/180823a.gif
About 22dB S/N in 278uHz, about -14dB in 1Hz.
--
Paul Nicholson
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Ё! Пойду в сарай найду макет уся на TDA7294.
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Нашёл. Теперь БП надо восстановить.
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С этой же антенной Стефан передавал DFCW-90 на 8270 Гц
Hi VLF,
Along with some carrier transmissions i run some good old DFCW-90 on my
900m ground loop. At 1.8 A antenna current i easyly saw the signal in a
QRSS/DFCW-60 spectrogram (22 mHz, 10 sec scroll rate), spectrogram
attached. Like on LF, the QRN increased at midday.
For this frequency it is a distance of > 1 wavelength. A short carrier
transmission running earlier showed 28.5 dB S/N in 2.8 mHz.
73, Stefan
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Стефан пишет, что собирается использовать эту антену на 137 кгц!
Hello Genosse Roman,
Yes, i used the ground loop also on 2970 Hz (and on 2470 Hz and 1970
Hz). On sunday i also run a 2 hour long carrier on 1570 Hz starting
08:08 UTC. The post-processing is running. I will report later. Next i
will try 970 Hz but also 137 kHz!
73, GL, Stefan
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Hello Roman,
The distance between RX and TX is 55.6 km in all these experiments, also
on 2970/2470/1970 Hz. The report for 1570 Hz (the 191 km band) will
follow today.
Unfortunately this loop has its minimum pointing to Russia and the ERP
is very low so it is most unlikely to receive a signal from this antenna.
But the ongoing transmissions on 17.4701 kHz could be received
relatively easily in 3000 km distance.
73, GD DX,
Stefan
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Вот такое вот QRO/P...
Roman, ULF,
Some more thoughts. This distance is in the far field for frequencies
down to 870 Hz. In my view, it is out of the range of 'local tests'.
Think about the GHz guys operating above 100 GHz. They deal with the
same distances and spend the same efforts and money :-)
It and it is my goal to go down as deep as possible. It is a pleasure to
work with this type of antenna and i can already see that it outperforms
my large inv-L below 3 kHz. The ease of use is fascinating. You don't
need a coil to resonate it and you don't need to hande high voltages
(although i like high voltages :-) ).
For this antenna, the limiting factor is the TX power and time! I need
to transmit from batteries and stay there during the transmission, so i
can't run a carrier for weeks. But i could apply 2 kW! :-) So far i
managed to apply 255 W (RF) and the goal is to reach 500 W.
In a next step i need to improve the RX site since the small loop
becomes quite deaf below 2 kHz it seems.
73, Stefan
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ULF,
Last sunday i finally managed to detect a carrier transmission on the
191 km band in the far field. In fact the distance is higher than 1/4
wavelength. A new lowest frequency of a signal generated by amateurs,
detected in the far field.
At 250 W RF power i transmitted for 2 hours (starting 08:08 UTC) on my
900m long ground loop antenna. It seems to be a very hard band with poor
propagation. Furthermore my RX antenna becomes deaf below 2 kHz. So the
S/N is much lower as expected when comparing to the results at 1970 Hz.
Two spectrograms are arrached, showing the short trace in 424 uHz and
212 uHz.
Before finally entering the far field in the frequency range below 1 kHz
it may be necessary to build up an E field RX at the RX QTH. I first
step for that was done yesterday.
To be continued...
73, Stefan
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Стефан провел по мей просьбе эксперимент с антенной из отбойника на 137 кГц!
Genossen!
I just matched the antenna and run some WSPR-2 transmissions on 137.425 kHz.
I'm getting 260 mA antenna current at 10 W RF power. So the overall loss
resistance should be 150 Ohm (the wire has about 30 Ohm). For resonating
i need about 2.5 nF in series to the wire.
So the feed point impedance is Z = 150 Ohm + j450 Ohm, still behaving as
a loop. Quite a comfortable managable impedance. I had to wind an output
transformer on a "RIK20" core (Reichelt!), which works very well. The
secondary number of turns was unknown at the beginning ;-)
Regular transmissions will start in an hour or so.
73, Stefan
Hi Genosse Stefan,
2018-09-08 11:56 DK7FC 0.137425 -17 -1 JN39 1 DL4RAJ JN68kj 449 103
2018-09-08 11:56 DK7FC 0.137425 -11 0 JN39 1 DL0AO JN59vk 349 89
2018-09-08 11:08 DK7FC 0.137425 -10 0 JN39 1 DL0AO JN59vk 349 89
2018-09-08 11:56 DK7FC 0.137425 -22 0 JN39 1 PI4THT JO32kf 306 359
2018-09-08 11:08 DK7FC 0.137424 -22 0 JN39 1 PI4THT JO32kf 306 359
2018-09-08 11:56 DK7FC 0.137429 -18 0 JN39 1 DC0DX/RF JO31lk 218 0
2018-09-08 11:56 DK7FC 0.137425 -26 0 JN39 1 DC5AL-R JO31lk 218 0
73
Clemens
DL4RAJ
RR,
Now, since 12 UTC the TX is in its final position and runs each 10
minutes. It will run for 24 hours or so.
So far the results are quite satisfying, for just 10 watts. With 100 W,
we could have a CW QSO in the groundwave range. Did you expect that?
Let's see what the night brings. Also the radiation pattern will be
interesting...
More reports from more stations are welcome :-)
73, Stefan
Его также принимал Крис 2E0ILY:
1350 -26 -0.1 0.137424 0 DK7FC JN39 30 772
Hi Stefan,
indeed your signal has been very consistent around 5 uV/m and -8 to -10 dB in the afternoon. At 230 km range, this would indicate a radiated power around 40 mW (EMRP), or 0.4% antenna efficiency. Around nightfall, heavy QSB set in, with occaional minima where the signal fell below the decode threshold but was still ghastly visible in the waterfall with heavy RDF colour aberrations. I suspect that the diplole emits more high angle radiation than a vertical, possibly leading to deeper fading at intermediate ranges.
Best 73,
Markus (DF6NM)
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Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
2018-09-09 03:30 DK7FC 0.137425 -27 0 JN39 1 SM3LNM JP82qg 1559 20
2018-09-09 10:30 DK7FC 0.137425 -24 0 JN39 1 2E0ILY IO82qv 767 303
2018-09-09 04:10 DK7FC 0.137425 -25 0 JN39 1 G3XDV IO91vt 568 300
2018-09-08 12:20 DK7FC 0.137424 -16 0 JN39 1 DL4RAJ JN68kj 449 103
2018-09-09 10:20 DK7FC 0.137425 -7 0 JN39 1 DL0AO JN59vk 349 89
2018-09-09 01:20 DK7FC 0.137426 -24 0 JN39 1 PA0RDT JO11tm 327 315
2018-09-09 16:30 DK7FC 0.137425 -21 0 JN39 1 PI4THT JO32kf 306 359
2018-09-09 07:30 DK7FC 0.137425 -6 0 JN39 1 DF6NM JN59nj 301 90
2018-09-09 01:40 DK7FC 0.137429 -14 0 JN39 1 DC0DX/RF JO31lk 18 0
2018-09-08 21:50 DK7FC 0.137424 -28 0 JN39 1 DC5AL-R JO31lk 218 0
2018-09-09 00:50 DK7FC 0.137425 -27 0 JN39 1 DF2JP JO31hh 205 354
2018-09-09 07:50 DK7FC 0.137425 +1 0 JN39 1 DK7FC/HD JN49ik 127 91
2018-09-09 09:50 DK7FC 0.137425 0 0 JN39 1 DL1GCD/1 JN48ar 115 136
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Сию дискуссию, считаю полезной оставить у нас тут.
Hi Jim,
(I changed the subject.)
Well, i remember there was a day where Markus transmitted on 8270 Hz, and me too. We were both visible on Paul's grabber.
Markus told me i was about 5 dB stronger there. Here is a spectrum from Pauls grabber (me on 8270.000 Hz) http://78.46.38.217/fbins3.html#p=1532887200&b=120&s=pw&m=cardioid&w=r&h=42&z1=0.34&z2=0.64&c=1&mb=632,136,655,212,1
Well the Distance from Paul to Markus is 1028 km, the distance to my ground loop is 840 km. Markus used an E field antenne, i used a H field antenna, so there may be some better filter and antenna mixing coefficients for one of the stations. Let's say, due to the different distances, i have an advantage of 1.8 dB.
Markus states he emits 10 uW (i guess that is EMRP) so my signal seems to have about 20 uW EMRP during that transmission, in which i run 550 mA antenna current.
Meanwhile i can run 1.8 A antenna current (+10.3 dB), so the signal could have 215 uW. That is with 255 W RF power. So the antenna efficiency is about -60 dB at 8270 Hz, based on Markus' 10 uW statement (?).
I have no idea if the equivalent loop area actually increases with a dropping TX frequency. On LF it seems to do at least :-)
Assuming the area is constant, the efficiency will be even 14.4 dB lower on 1570 Hz and 18.6 dB lower on 970 Hz. Uuuh i hope this is not true :-)
So the EMRP on 1570 Hz was maybe 8 uW at a -74.4 dB efficiency.
73, Stefan
Am 10.09.2018 08:19,
Свернуть
Hello Markus, Stefan, Paul,
Is there any way of guessing the ERP of the 1570 Hz (or 2970 Hz) earth-loop tests last week?
I noticed that ERP/wallplug-power efficiency of the Norway (Dazey) test at 1280 Hz might extrapolate to about 2E-8 with 1 km between electrodes (with ~ 20 ohm electrode-to-earth resistance); and though it might be informative to compare.
73,
Jim AA5BW
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Hi Jim,
You can still find the single decodes in the WSPR database. Most of the reports were with the wire in loop configuration (ends grounded). This gave clearly better results! I switched to the dipole config yesterday 09.SEP. 17:38 UTC
Yes, 10 W RF out, at least in the loop config.
73, Stefan
Am 10.09.2018 16:35,
Свернуть
Hello Stefan,
Excellent results, and fascinating.
For the 13 WSPR reports below, is the antenna in dipole-on-ground mode (ends not grounded) or in earth-loop mode (ends grounded)?
Was the 10W that you mentioned the power-amplifier output power?
73,
Jim AA5BW
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передатчик Стефана участвовавший в сей серии экспериметов. (http://www.iup.uni-heidelberg.de/schaefer_vlf/LF/20180909_192539.jpg)
оформил ссылочкой - там оч большая картинка. открывайте в отдельную вкладку.
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-перенесено
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-перенесено
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970 Гц с земляной антенной. (http://136.su/index.php/topic,403.msg22169.html#msg22169)
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Эксперимент Рикардо IW4DXW на 8270.003 Hz с земляной антенной и телеуправляемым ТХ. Передавали Ebnaut. (http://136.su/index.php/topic,6.msg22243.html#msg22243)
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Еще один успешный эксперимент Стефана DK7FC с антенной из дорожного отбойника. (http://136.su/index.php/topic,423.0.html) 2970 Гц
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;D
катаюсь!
Hi VLF,
You probably know:
IOTA - Islands On The Air
SOTA - Summits On The Air
but did you know
GOTA - Guide-rails On The Air ??!!
The year 2019 should be the year of GOTA! Try it out. You can do it! No
excuses like problems with the large coils, the high voltages, the XYL
occupying the garden. Just go out, take a walk, and see what you can do
with some wire and a transmitter and some other equipment! :-)
73, Stefan
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Hi VLF,
Last weekend i improved my ground loop antenna by increasing its length
from 900m to 1130m, i.e. +25 % of length, which should give about 2 dB
more signal from the same antenna current. This is, when assuming that
the shape of the virtual ground loop is rectangular.
Now when having two antenna segemnts it allows to do more research:
1. The resistance of each earth electrode can be calculated.
2. the shape of the virtual loop can be estimated: The resonance
capacity (to series-resonate the R-L network at the feed point) can be
compared for the 900m segment and the new 1130m segment. For a
rectangular loop shape we would expect that the L rises with the square
of the length.
The old loop was in an angle of 54 deg to my tree. This angle changed to
45 deg now.
I expected a theoretical gain of
G = 20 * (lg(1130/900) + lg(cos45/cos54)) = 3.58 dB.
A carrier transmission was done at 8270.1 Hz, using an antenna current
of 2 A on both antennas.
900m Ant: T2019-03-31_13:58,+10m : E-field 26.8 dB, H-field: 33.7 dB
1130m Ant: T2019-03-31_14:12,+10m: E-field 31.2 dB, H-field: 37.1 dB
Looks like an improvement of 4.4 dB in the E field and 3.4 dB in the H
field.
Attached is a spectrogram (11 mHz FFT bin width) showing the
improvement. The first dash is a tunng procedure, second is the 900m
ant, and the 3rd is the 1130m ant. Top is E field, bottom is H field.
I wonder how the level difference looks at other locations? Did someone
else track the data and can tell me the difference? :-)
73, Stefan
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At DL0AO, we produced spectrograms and plots during the 5.17 kHz test last weekend. During the first session with the shorter guiderail antenna, signficant fading and a dip occured, most pronounced on the H-field receive antenna. Another deep dip happened immediately after Stefan switched to the long antenna, however that period may perhaps have been affected by a short retuning interruption at 12:58. Considering around 17 dB SNR in 1.5 x 3.8 mHz, the 6 dB variations seems to be too large to be explained by random noise alone. Thus we have been speculating about ionospheric variations or scintillations on a ten-minute timescale. Note that no solar x-ray or SID event had happened at the time.
Therefore I asked Stefan to repeat the test, which he did today, this time starting on the long antenna (10:39 - 11:15) and then going to the short one (11:19 - 12:10). This time the SNR was even better, and only small variations occured, perfectly within the range of noise statistics.
Best 73,
Markus (DF6NM)
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Hi Paul,
Thanks for your measurements.
Good idea to calculate B relative to I.
Would be interesting to see how this varies with frequency.
BTW i did now actually order one of those:
https://www.dhgate.com/product/60-v-60ah-lifepo4-60-v-60ah-lifepo4-de-litio/445395613.html#s2-21-1b;searl|3512104843
Wonder how long it takes to arrive here, and even more, if it actually
has 60 Ah at 60V, i.e. 3.6 kWh!! If so, i will order 3 more of them!...
Considering the 13 dB advantage of night/day in recent transmissions
with that ground loop antenna, at least on 8270 Hz, I'd like to try a
night transmission tonite, at 2970 Hz, trying a 7 character EbNaut
message. So far we have no message decode at ULF between DL and UK. I'd
like to reach that mile stone and think the ERP should be fine now, but
hopefully the QRN stays low enough.
Everyone else is invited to try as well!!!
73, Stefan
Am 05.04.2019 19:06, schrieb Paul Nicholson:
>
> Stefan wrote:
>
> > These were the transmissions today (+ some more parameters):
>
> Received at 5170.1 Hz,
>
> 2019-04-05_10:39,+35m: 1130m, I=2,39 A, 0.63 fT S/N -5.07 dB/1Hz
> 2019-04-05_11:19,+51m: 900m, I=2,92 A, 0.63 fT S/N -4.92 dB/1Hz
>
> Yes, the same fT in both tests. Then we have
>
> 900m
> ----
> 2.74 A -> 0.50 fT, 0.182 fT/A
> 2.92 A -> 0.63 fT, 0.216 fT/A
>
> 1130m
> -----
> 2.12 A -> 0.50 fT, 0.236 fT/A
> 2.39 A -> 0.63 fT, 0.264 fT/A
>
>
> Nothing received at 970.1 Hz.
>
> --
> Paul Nicholson