VLF: New DK7FC experiments on 17.47 kHz - Антенна из дорожного отбойника

[rw3adb]

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

[Сергей UB1APE]

Ё! Пойду в сарай найду макет уся на TDA7294.

[Сергей UB1APE]

Нашёл. Теперь БП надо восстановить.

[rw3adb]

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

[rw3adb]

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

[rw3adb]

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

[rw3adb]

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

[rw3adb]

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

[rw3adb]

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)

[rw3adb]

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

[rw3adb]

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

[rw3adb]

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

[rw3adb]

передатчик Стефана участвовавший в сей серии экспериметов.

оформил ссылочкой - там оч большая картинка. открывайте в отдельную вкладку.

[rw3adb]

-перенесено

[rw3adb]

-перенесено