Stefan, thanks for the congratulations!
We will be doing further experiments. This one was done in haste, and
could have been planned better, so for sure there is room for a lot of
improvement.
We (Marcin SQ2BXI and i) always try to do these experiments together,
since it seems there aren't more VLF enthusiasts in Poland. Unfortunately
this requires one of us to drive 350km to the other, and this is the
reason why we don't do them more often.
We are planning a longer ebnaut transmission, and we hope to draw a line
on your grabber this time :)
VY 73
Jacek / SQ5BPF
On Mon, 4 Mar 2019, DK7FC wrote:
Date: Mon, 04 Mar 2019 10:27:29 +0100
From: DK7FC <[email protected]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: VLF: ebnaut transmission from Poland
Hi Jacek, Marcin,
Well done! Congratulations to a first VLF signal coming from SP that is
detected over such a distance, more than 1000 km! This is truely encouraging
and shows what could be done by MANY amateurs, if they would just give it a
try!
A milestone for your country, from an amateur radio view.
Thanks for the details in that website. It is interesting to see that such
ground loop antennas seem to work even in regions where the ground
conductivity is expected to be quite high. Thanks to Paul's decode, you now
have the certainty that the signal actually propagates.
Well, the ground loop seems to radiate into Paul's direction and there is a
lot of water on your path (between you and Paul). Also we (DL0AO and DK7FC)
are closer to QRN sources in south-east Europe. This will contibute to our
negative decode result here.
On the other side we saw that the signal also propagates into unexpected
directions, at least as long as the QRB is lower than 2000 km.
It would be most welcome to see more activity from your side! And it looks
like you can rise the ERP by 10 dB without much effort. Are you planning more
experiments? And when? :-)
The EbNaut message was transmitted during a time where phase changes are
likely, because it was during the sunrise at your location. Maybe you can
repeat the experiment, using 2 characters transmitted over 6 hours, starting
21 UTC for example? That would help us, here in the south, to receive your
message.
I will have a look at my signal recording to see the SNR for the message 'SP'
later.
At 75W and 300V antenna voltage you had 250 mA antenna current and, as you
wrote, 1200 Ohm. If you have 500 Ohm DC resistance then i conclude that you
did not series resonate the antenna. The reactive component was j1090 Ohm, so
a series C of 177 nF (100+47+22 nF) would help to reduce the feed point
impedance to 500 Ohm. Not sure if you could then run a higher power but at
least the PA losses would be a bit lower.
With some cheap 0.75mm2 CCA loudspeaker cable you could reduce the wire
losses by about 90%.
All this is very nice promising!
Good luck and i hope to get a new chance to receive you here soon.
73, Stefan
Am 03.03.2019 19:44, schrieb Jacek Lipkowski:
On Sat, 2 Mar 2019, DK7FC wrote:
I've tried a lot of antenna mixing but did not get better spectrum peaks
that 10.5 dB SNR, so it is quite weak. Best decoder result was 'AV' at
rank 70.
The transmitted message was: SP
I'm waiting for your detailed description of the experiment. What antenna
and power was used? How did you generate signal?
A preliminary descritpion is here:
https://klubnl.pl/wpr/en/index.php/2019/03/03/nadawcze-proby-z-dipolem-ziemnym-w-zakresie-vlf/
Around 100W into a 500m long earth dipole, the signal was weak and we were
surprised to have Paul receive it (well, maybe not that surprised given
Paul's excellent receiver).
For the 8270.005Hz carrier we used a GPS generator module (i think it might
be just an uBlox GPS inside, but didn't investigate it). I think Marcin
bought it on some auction site.
For 8270.00073Hz we used an old Neoware terminal with an uBlox neo-7M GPS
installed inside. The gps is used to provide a coarse time reference (not
the best precision because the 1PPS signal is not used), and as a 20kHz
reference signal connected to the terminal sound card. The terminal runs a
slightly modified version of Paul's ebsynth, and some custom-written
software to control the gps. This is the same generator that i've used in
my other tests. I can publish some details in case anyone is interested.
VY 73
Jacek / SQ5BPF
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