Dear VLF,
Thank you very much for participating on that very successful activity! :-) It
was really exciting and funny to be QRV from the hill although i knew that
there will be no QSO, just transmitting. But it's exciting to see all these
details working in a system: The generator, the power supply, the PA, the coil
and wire and kite and wind, notebook, VFO, fiber optics and so on.
Congratulations to Bernd, Michael, Markus, Jim, Paul, Renato, Wolf, Uwe, Henny,
Victor (anyone forgotten?) to your successful RX results! Thank you for coming
out of the house and making the effort to try it from a /p QTH (e.g. Jim)!!
Especially crossing the alps to Italy into the first attempt without problems
is very enthusing for me!
Thank you Markus for supporting me all the infos and feed back! That's an
important job since i wouldn't know anything there up, if my signal gets
received.
Also tnx to all who have tried to catch the signal. Maybe you got an idea what
to do next, to improve the system. And the next time you will have it! It seems
that reception in a few 100km is possible even without such a professional
optimised system like Pauls!
Now, it seems to be claer even for the strongest sceptics that a signal <9 kHz
can be radiated and received by amateurs a few hundred kilometers above the own
garden fence (i do not even have a garden fence), even with ID. On Markus
grabber in 180km, the DFCW120 message was clear, probably the first "73" by
hams there.
As an attachment you see a screenshot of Bernd/DF8ZR who was also QRV in 16km
distance. He imrpoved his system by resonating his wire antenna with a ferrite
pot coil and a small parallel C. He recorded with Spectrum Lab in QRSS120 mode
and got all of my messages with nice SNR (best ever there)!
As you can see the PA even transmitted between the caracters. For DFCW is used
Rik's QRS program. In LF it works fine but here it seems that i have made a
mistake in soldering or choose not the correct settings (new old notebook, so
new installation of the QRS program). Will work the next time! But maybe it is
even better, running the PA as long as possible when beeing there?!?...
Now, like always, a longer report of the activity, for those who are interested:
I started improving my TX system in the late evening on saturday. First,
replacing the PA fuse from 10A to 16A (very slow type, and cooled by the wind,
so 20A CW wouldn't be a problem).
Next, replacing the digital Amperemeter (20A) by a analog Amperemeter (40A!).
I haven't found the time to built the new PA yet but in this evening, my main
interest was making DFCW possible.
Since i am using rather old notebooks and surely will have some temperature
drift there on the hill i decided that using the Spectrum Lab signal generator
is not optimal for this /p acty (since i have no additional receiver for a
reference signal for a temperature drift compensation and so on).
So i modified the incremental turning wheel for frequency adjustment. This
device has 3 pins, one is ground and two are signal pins. Depending on the
signal (high or low) it is differenciated between increment and decrement. So i
built a circuit out of some CMOS NAND gatters (4093) and some Rs and Cs that
generated these signals, depending of the edge of the DFCW signal of the RS232.
This worked very sufficient as you can see.
Additionally i realised an switching of DFCW and keying the PA by 2 fiber optic
cables. The TX LEDs are directly fed by the RS232, giving arround 10mA per
channel. Triggering the PA works also very fine.
But then, as i finished all this, it was 5 UTC... So i slept just 4,5 hours and
got up to drive on the hill. During that, the rain stopped, the sun came out
and the wind increased!! What do we want more? :-)
I found the second part of the broken steel wire of the last acty and put the
old wire together again :-) Then, after coming up, the wind turned and dropped
the coil on the ground. Since that time i place it behind the kite braid, so it
can do what it wants.
I had the idea to put a 2m long cable in series to the SMPS, to damp the
described oscillation of the generator. That worked also very fine! Thus, i
could even increase the output voltage of the PA, so there was slight QRO. This
QRO was in the second "K", and you have already mentioned that this K was
stronger, so you saw the difference ;-) The wind was strong and the kite was
mostly well above 60 deg, i estimate 50% above 70 deg. The power was up to
300W, so 2mW ERP, also a new record for me ;-)
I will place some additional Photos of the recent modifications on my site @
qrz.com (VFO, fiber optic RS232, PA...)
After transmitting "DK7FC/P 73" in DFCW 120, the rain started and so i quit the
operation since water on the coil with 16kV is no good idea...
.-.-.
Further improvements will be (still) QRO by 3 dB and i will start to think
about ground systems to even reduce the 450 Ohm earth losses! I want to reach
the voltage limit where the PDs make more voltage on the wire impossible. 16kV
rms seems not to be the limit :-). But i assume the limit of the coil is
something about 40kV rms.
Today i got a call from my insurance, that i get the confirmation that is
required to get the permission for a 300m kite. That would be almost a 5/8 wave
for the 600m band ;-) I will ask what is the absolute limit. Maybe i can built
a 1/4 wave for 137kHz? ;-) Will see...
So, now it seems that there have to come up further TX stations!! There are so
many RX stns now who want to catch other stations as well i assume :-)
Let's discuss about improving RXs. Just like PA0RDT said, i assume that there
can be much achieved with active E-field probes, probably with a larger probe
(?). There are many fields where we can squeeze out some dB S/N and maybe we
can go from DFCW600 to DFCW60 in some time.
Dreaming is the key of success it seems, so let's do it :-)
73, Stefan/DK7FC
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