Also my congrats to all involved. If things
continue to proceed at this speed (within some
weeks from pure theoretical thoughts to a
reception at over 800km) the big pond should be crossed by Easter ;-).
I had a look at Markus LF grabber and noticed a
clear "dip" in background noise around noon, maybe this is the right time ?
73, Rik ON7YD - OR7T
At 09:02 16/03/2010, you wrote:
Hello all
Congratulations to Stefan.
Mathematically it might have been clear that
this is possible. Not really my business, But YOU just DID it.
I was not with the doubters but I never had
expected such success after such a short time.
Just a few weeks ago I started the thread with a
simple question . more or less something like:
Has someone crossed his garden fence below 9kHz, hi. The response was amazing.
Unbelievable that even the few experiments below
9kHz had stopped for such a long time after the
90s, even in DL after the Bundesnetzagentur
estimated that frequencies below 9kHz are free -
but officially not ham radio. The few interested
in this band have worked as single experimenters
until the discussion on the reflector became so encouraging. Real HAM radio!
I am happy with Stefan and also Markus. And I am
looking forward to who of us is next.
Horst
-----Ursprüngliche Nachricht-----
Von: "Stefan Schäfer"
Gesendet: 16.03.2010 01:15:17
An: [email protected]
Betreff: AW: LF: DK7FC's 2nd VLF TX test...
>Dear LF group, RXers and 9Dreamers and doubters,
>
>Thank you for your assistance on that very
successful experiment! It is a good day for the
VLF ham operations and it won't be the last.
YOU are a part of this success since i wouldn't
have done all the effort to become QRV there if
you all wouldn't have been so interested in the discussion about <9.
>
>So, perhaps there will come up further TX
stns, i hope so. With the results we can see
what can be reached with a given ERP in a given
distance. So, all the theoretical calculations become less speculative...
>
>First, i confirm that i was QRV to the described time at 8,9700kHz.
>
>I will detailed describe now what happend on this experiment.
>
>Starting with buying a plastic spray paint and
fixing the windings on the water barrel was the
first work. Than applying the variometer and the primary coil.
>
>The primary coil is inductive coupled to the
secondary and isolate mounted on the bottom
side of the water barrel. It has just 9 turns
out of 4*0,4mm diameter isolated copper wire.
The 9 turns was an estimation but later it is
shown that it is optimal for getting the
maximum output power at moderate voltages and currents.
>
>On http://www.qrz.com/db/DK7FC i will show
many photos i have taken on the hill. So there
may come up some questions and some may be answered by the pictures ;-)
>
>After building up the kite (the 8,1m^2 type
due to a little unstable wind) and applying the
whole equipment i started some resonating
tests. The variometer part has a litte too much
L so it is sensitive to adjust but never mind.
It was easy to resonate and after transmitting
a long carrier i noted that the heat sink of
the PA remained absoultely cold. Then i
increased the output voltage and got an average
DC current (PA input at 13,8VDC by a SMPS
driven by my fuel generator) of about 13A
during the whole transmission time. The PA
still remained cold but it was fused with 10A
and i had a amperemeter of 20A full range, so i
didn't further increase the power. The current
came up to 18A and go down to 9A during the kite movement.
>
>During the whole transmission, there were no
HV problems! Just one time the wind turned and
suddenly the antenna wire got disconnected with
a 8,97kHz noisy 2cm long spark ;-) The DC
current immediately decreased to < 1A so that case is no problem for the PA.
>
>I was in telephone contact with Bernd/DF8ZR
and started to transmit some undefined
sequences. Later i built up the notebook and
installed the LF sequencer and keyed the TX in
QRSS30. Bernd copied it difficultly in a
distance of 16km. He clearly catched a 2
minutes transmission to that time i transmitted it.
>
>I forgot to take the 1 Ohm current shunt
resistor and the probe to watch/measure the
current with the oscilloscope but later i
rembered that i have a "true rms" digital
multimeter with a range up to 10 kHz and so i
could easily measure the accurent antenna
current. The average antenna current was about 480mA!
>
>So, the voltage was abt 15kV rms. Since there
were no HV problems there is the possibility to
increase the ERP at least by 3dB.
>
>Andrey: No, the coil does almost not sing. The
sound of the PA transformer is louder (only a
little, not too nerving) but all that is blown in the wind ;-)
>
>Paul: My exact QTH is
http://maps.google.de/maps?hl=de&ie=UTF8&ll=49.77647,8.699525&spn=0.001607,0.003428&t=h&z=18
(see the coordinates in the link). So: >Bearing
of this signal was 117/297 deg. Frankfurt is
on 114. This is pretty exact! Congrats to your
RX antenna system, Paul, very fine!! So, what
is the new WR? I do not have a program that
calculates the distance accuratly out of the coordinates...
>
>Later i got a mobile call from DF6NM who told
me that the signal is visible on his grabber.
To that time i tried an unsuccessful QRSS10
test with Bernd. Later i switched to QRSS120 to
write "DK7FC/P" there but it took 2,5 hours
just for these few letters. Finally i just
transmitted "DKM" since during the "7" the
antenna wire (copper+steel-litz) broke. You can
clearly see the "M" at the DF6NM grabber, the
last sent letter for this day. The broken wire
was due to strong wind: The kite needs a braid
that is elastic (110% length at maximum force)
to withstand the wind blasts, so the ant wire
needs to have some sag and this sag was not
enough in that moment, so the whole force
turned to the wire. No problem about the wire,
i have enough for the next test...
>
>To the earth resistance: R(coil)=300Ohm and
P(PA (with abt 100% efficiency))=180W, so the
earth resistance seems to be about 480 Ohm.
Hmm, seems to be a little much but it includes
all the other additional losses such as coil
losses due to the H stray field near the
earth... I will measure this more accurately
the next time. BTW i measured the voltage
waveform with a loosely capacitive coupled HV
probe. The sinus form was OK but could be
better. But the C coupling is a high pass and
so the harmonics may be not so strong as
displayed... Listening to the harmonics with my IC706 gave nothing, nice.
>
>My first question (others surely will come up
later): What is the achievable groundwave
distance on the 33422m band? ;-) And what do
you expect is possible at night? Maybe, if we
now have 830km (?, not 840?) we could even get much more...
>
>Maybe i have forgotten to answer some
questions but this mail is already long enough.
So, will go on tomorrow. Now uploading the pics...
>
>73 es GL, GN, 9 dreaming...
>
>Stefan/DK7FC
>
>
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