форум Радиолюбительского ДВ портала > ДВ антенны
EARTH ANTENNAS - Земляные антенны
rw3adb:
Эксперименты Марцина с земляными антеннами. Пишет Стефану в РСГБ.
Забавный эксперимент с мостом железным 3 км длинны в качестве антенны.
From my experience, erth dipole work best on 630m. Unfortunately, in the north of Poland, the soil is well or very conductive. In rocky ground you can get much better results. I am waiting for autumn to continue my experiments.
https://klubnl.pl/wpr/en/index.php/2018/01/09/most-na-wisle-elementem-anteny-czyli-eksperymentow-z-dipolami-ziemnymi-ciag-dalszy/
https://klubnl.pl/wpr/en/index.php/2017/11/26/kolejne-proby-z-antena-dipol-ziemny/
I am looking for a power generator for power supply in the field. Can anyone recommend something?
73! Marcin SQ2BXI
rw3adb:
Стефан тут планирует использовать отбойники на дороге как земляную антенну, а LA3EQ уже ипользовал и хвастается!
Тема проходит в рсгб, но там потом хрен что найдешь в архивах переписки, оно весьма затруднительно, посему наиболее интерестное и практически полезное для нас лучше отображать у нас, здесь.
Hello Stefan
A very interesting idea for an experiment.
Looking at the video below should get good results.
https://www.youtube.com/watch?v=sWsdaSmWg7E
73! Marcin SQ2BXI
From: owner-rsgb_lf_group@blacksheep.org <owner-rsgb_lf_group@blacksheep.org> On Behalf Of DK7FC
Sent: Sunday, July 22, 2018 8:28 PM
To: rsgb_lf_group@blacksheep.org
Subject: VLF: Earth antenna transmissions on a guide rail?!??
Hi all,
During the weekend i am in the Pfälzer Wald again which is such a nice place to be! I already installed a fixed E field antenna for VLF/ULF reception in JN39XI06 :-)
Now i have the idea to use a guide rail (attachment!) as an electrode for a earth electrode antenna! There is a perfect road which is not much frequented and where no way is crossing so i could temporary install a long wire on the ground between two of these guide rails. I would assume they provide a good grounding. They are located on a relatively high hill/mountain with stony ground. The mountain is very steep there and in some distance, 200m deeper, there is a brook..
With some luck the ground losses can be near 200 Ohm? Maybe rather 300 Ohm. I'm going to prepare things and plan to transmit for some time next weekend. If the ground loop actually acts like a loop, the bearing should be 135 deg, so it will be in a 45 deg angle towards my QTH where my grabber is listening in 55 km distance. That's quite a good distance for testing! I'd like to try LF and VLF, maybe ULF it all works well.
A BTW the wire length will be 860 m! However there are two guide rails in a shorther distance, about 450 m. I will try the shorter length first, to get an impression of the loss resistance and to see if something is visible at all :-)
73, Stefan
Р6ЛДД:
Кто-то из немцев или итальянцев уже пробовал с отбойниками, найду - выложу.
На VLF.it про земляные антенны:
http://www.vlf.it/ed/earthprobes.html
rw3adb:
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
rw3adb:
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.
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