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

Jacek,

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
produced
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