IW4DXW<>DK7FC 8270 Hz Ebnaut experiment

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Смотрю, они там приспособились довольно длинные сообщения уже слать... - [VLF TU DECODE]
Так за пару тройку ночей можно и QSO провести!)

Hello Riccardo,

Very nice! No problem to decode again. Best result was:

found rank 0 ber 3.5227e-01 Eb/N0 2.4 M -8.090035617e-02 ph 48 60,30,30,0 [VLF TU DECODE]
carrier phase: -5.9 deg
carrier Eb/N0: 2.8 dB
carrier Es/N0: -10.94 dB
carrier S/N: 21.52 dB in 37.9 uHz, -22.70 dB in 1Hz, -56.68 dB in 2.5kHz


This morning the QRN was very very low, it invites to transmit something. I should think about it this weekend :-)

73, Stefan

PS: Don't stop transmitting if possible :-) I like the messages a lot. And as you can see, a 20 charcter message would have been easily possible in the same time!


Am 26.11.2019 20:28, schrieb Riccardo IW4DXW:

    Свернуть

    Hi VLF,

    I think I've solved the isolation trouble.
    So, before another day of bad WX, I'll try again another message:

    f = 8270.003 Hz
    Start time: 21:00:00 UTC
    Symbol period: 15 s
    Characters: 13
    CRC bits: 12
    Coding 16K21A
    Duration: 7h, 20min
    Antenna current: 660 mA

    Reports are welcome.


    All the best

    73 de Riccardo IW4DXW

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Ciao Riccardo,

Now your transmission is completed. Here is the result i got from the H-field (single turn loop, 1.2 m diameter, non-resonated, preamp):

found rank 0 ber 3.0526e-01 Eb/N0 4.8 M -7.284875214e-02 ph 0 0,0,0,0 [TU DK7FC DE IW4DXW K]
carrier phase: 2.2 deg
carrier Eb/N0: 5.1 dB
carrier Es/N0: -8.48 dB
carrier S/N: 25.71 dB in 38.1 uHz, -18.48 dB in 1Hz, -52.46 dB in 2.5kHz

Best result from the E-field is: carrier S/N: 23.78 dB in 38.1 uHz

The phase is stable, a difference to the nights. Probably the daytime signal is weaker but the S/N is higher. Most interesting and your signal is really good.
If you still like to try something, we could try to come a bit closer to the limits. What about 40 characters, like:
http://abelian.org/ebnaut/calc.php?sndb=25.7&snbws=0.000038&snmps=&code=16K21&sp=6&crc=12&nc=40&submit=Calculate

73, Stefan

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Описание аппаратуры для этого эксперимента.

Hi Stefan, Roman, VLF.


OK, Stefan! Thanks again for the decode, congrats: you don't lose any electron from my antenna!  :-)
Yes, my antenna: it's not a big deal :-) so that is why I invite all LF friends to try QRV on VLF.
It's a simple "L inverted" Marconi 13 meters high with a top hat 35 meters long (which is composed of 3 parallel wires for a total capacity of about 500pF). The feeding point is located about 8 meters above the ground.
The TX signal is generated by a Win7 PC (an old 4core) with SpecLab using a NEO-M8T 1PPS reference and running a PLL configuration.
The system locks a signal from an antenna current probe (0.9 ohm precision shunt) located on the cold point of the loading coil.
A 500W power rating homebrew PA (p.p. 2 x IRFP260) feeds a toroidal 1:80 trafo connected directly to a 750 mH loading coil (manually adjustable with a moving ferrite core).
About RX setup, Stefan, I'm almost ready with a new miniwhip antenna and a USB Creative Soundblaster X-Fi. More news coming soon...

All the best


73 de Riccardo IW4DXW




Il Gio 28 Nov 2019, 20:05 DK7FC <.de> ha scritto:

    Свернуть
    Hello Genosse Roman,

    Here on the RX site it is my 'old' system on the tree, which is
    meanwhile running since 4 years! I have two orthogonal loops and an E
    field antenna. The 3 channels are sampled synchronuously from a sound
    card having 6 input channels. the 4th channel is used for a PPS ref
    signal. NMEA data is also used to identify the right second. The last 2
    channels are used for 472 kHz. It is running on a Raspberry Pi Model 2B.
    The data is streamed over 3.5 km distance to the city where i built up
    my own network (battery backup) to stream the data to a PC which records
    to a 1 TB HDD, covering about 40 days. It is all running on Linux... I
    can post-process the 3 channels and mix the antennas, to form a cardioid
    beam, and apply a filter and a noise blanker. The stream, is also lead
    to a Win7 PC running the SpecLab instances for the grabber at
    http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html
    Meanwhile there are 4 Raspberry Pi involved in the data acquisition and
    distribution and preparation. These days i'm testing SpecLab running on
    a Linux machine, which has some advantages...
    The circuits for the preamp have been shown in the last years, but if
    you really need them again, i can check if i can find a drawing of the
    latest modification...
    Oh, and: The system on the tree is solar powered since the first day. 3
    x 50 W modules are installed there and meanwhile i installed a '12V',
    120 Ah LiFePo4 accu up there which is discharged by 6.4 Ah each day, if
    there would be no sun at all. It is the hardest time in the year now of
    course. It is not the short time the sun is out and it is not the lower
    angle but it is the couldy wx that we have since weeks :-(
    That's my short story.

    Now it's Riccardo's turn. I'm also interested in his story since i don't
    remember all details of his antenna and so on.

    73, Stefan