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Re: ULF: EbNaut message transmitted from ground loop

To: [email protected]
Subject: Re: ULF: EbNaut message transmitted from ground loop
From: DK7FC <[email protected]>
Date: Mon, 08 Apr 2019 23:39:37 +0200
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Hello Jacek,

Most interesting. Did you expect at all that you catched the signal? Below 3 kHz over that range, we thought it is completely impossible for amateurs, didn't we?
Let's keep on trying!
Best i got so far is 15.05 dB, also with no decode so far.
I have no problem to repeat the experiment in some a few weeks, we could start with a 5 character message, that would have been successful already. Some more improvements and some QRO is planned for the next time.
Did you use your large computer at work to try to get the best result?

73, Stefan

Am 08.04.2019 22:44, schrieb Jacek Lipkowski:
this is the best i can do:

~$ vtblank -v -a30 -t80 -d0.0008 < pliktmp | vtmult -f 2970.1 | vtresample -r 240 | vtresample -r 10 | vtraw -oa | ebnaut -dp16K21A -r10 -c4 -v -f15 -f16 -M'DK7FC/P' -k16 -S6 -N7
vtblank: selected channel: 1 = -:1
vtblank: channels: 1, sample_rate: 48000
vtblank: hfactor: 0.000e+00
vtblank: afactor: 30.000
carrier phase: -102.8
carrier Eb/N0: -0.9 dB
carrier S/N: 15.09 dB in 133.5 uHz, -23.66 dB in 1Hz, -57.64 dB in 2.5kHz
vtblank: end of input
vtblank: dropsum 0 17485057, nfp 359999999
vtblank: dropfactor 0 4.857e-02

unfortunately i still can't get a decode with -f9

maybe try a few characters less or longer symbols next time.

VY 73

Jacek / SQ5BPF

On Sun, 7 Apr 2019, DK7FC wrote:

Date: Sun, 07 Apr 2019 17:54:05 +0200
From: DK7FC <[email protected]>
Reply-To: [email protected]
To: [email protected]
Subject: Re: ULF: EbNaut message transmitted from ground loop


I'm right now trying to decode the message from your stream recording. First i did not expect much but a first attempt with vtread -T2019-04-06_20:25,+125m /jacek | vtcat -p | vtfilter -a th=4 -h bp,f=2970,w=1800 | vtblank -v -a23 -d0.0005 -t100 | vtmult -f2970.1 | vtresample -r240 | vtresample -r10 | vtraw -oa | ebnaut -dp16K21A -r10 -c2 -v -f15 -f16 -M'DK7FC/P' -T0.3 -k16 -S6 -N7
carrier Eb/N0: -1.4 dB
carrier S/N: 14.65 dB in 133.5 uHz

Wow, this already crossed the 14 dB criterium for significant spectrum peaks! A 5 character message would already ecode clearly now! My data from you has passed a vorbis encode/decode stage, so maybe it is possible for you to get a decode from the raw data? I'm telling the best result later. We are close to a decode! And that would be a new record distance for amateur radio at ULF.
All this rises new questions about radio propagation because my loop
does not at all point into your direction!
73, Stefan

Am 07.04.2019 12:49, schrieb Jacek Lipkowski:
      On Sun, 7 Apr 2019, DK7FC wrote:

An OM (OT!) of my radio club told stories of his early radio experiments. He had a friend in some 100m distance and they lay out a small hidden wire into they ground between their QTHs, using the earth as the back 'wire'.

Some electricity (i think they didn't call it electronics back then) hobby books for boys in the USA has descriptions of using ground dipoles for telegraphy. The transmitter was a buzzer-like circuit with step-up transformer, and the receiver was just high impedance headphones. Unfortunately i don't have the book, but i remember it also showed how to make a rhumkorff generator from a
      ford t ignition coil, so it must have been very old.

I also remember reading somewhere that during the war (not sure it was WW II) using amateur radio equipment was prohibited, and the ARRL advised using similar equipment, so that people don't loose their operating skills.
 No doubt some people used much larger ground dipoles than
advised in the books :)
      VY 73

      Jacek / SQ5BPF

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