Новости LF/VLF/ULF/SLF/ELF > VLF (ОНЧ — очень низкие частоты) диапазон с частотами от 3 до 30 кГц
VLF: New DK7FC experiments on 17.47 kHz - Антенна из дорожного отбойника
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
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