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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