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Re: LF: Re[2]: VLF: Trying 12 chars on 5170.1 Hz

from [DK7FC] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: Re[2]: VLF: Trying 12 chars on 5170.1 Hz
From: DK7FC <[email protected]>
Date: Thu, 18 Jan 2018 09:50:45 +0100
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Hello Alex,

Thanks for your report, the effort and the good cooperation. I think we both didn't expect that we can transfer messages on such low frequencies. My congrats to your good RX system, again.

12 characters, not a short message.
For comparison: On MF you can do it in JT-9 in 1 minute. On VLF, this transmission took 12544 minutes!! :-) But it was the first real message (apart from the 1 char message) from DL to RU on that band!!
12544, that's more than the square of the ratio of the frequencies (475/5.17)^2.

I've made some effort and generated stacks for the sum of all days from 1 to 14 (1, 1+2, 1+2+3, 1+2+3+4....). Then i checked the Eb/N0 by using the Linux decoder. A made a plot for the developing Eb/N0. We can see that after 13 days, the Eb/N0 was good enough, even a bit better than after 14 days. See attachment.
Do you have the files for the last 3 days? It would be interesting to complete the stack and see if we can get rank 0 when using all 17 days...

So now the next challenge is already waiting :-)
My ALC regulator of the TX  (SpecLab) is already on the limit although i'm now using 100% of output turns. On 5170 Hz it was just at 85% of the turns. But now there is another bucket in the stack and so the DC resistance is higher, higher than just +15 %. So maybe tomorrow i need to add a few more turns on the output transformer before the EbNaut transmission begins :-)

73, Stefan





Am 17.01.2018 17:03, schrieb Alex K:
Hello Stefan, VLF!
I am glad to report that 12-char message on 5170.1 Hz is successfully decoded near Moscow. My congratulations to Stefan!
Also I made some mistake in the SpectrumLab's settings (32678 instead of 32768) and all ebnaut-files were exported with the wrong length. So councils from Stefan and Markus how to correct it were very useful! Thanks!
In stacking procedure were used ebnaut-files from 29Dec - 14Jan.

So... 73 to Deutschland!
:-)

ebnaut-rx V0.7a
input file C:\EbNaut\DK7FC-12ch-5170\sum_dk7fc — копия.wav
sample rate 0.514403 per second
rx frequency 5170.1
file start time 2018-01-14 14:32:26.360
polynomial 16K21A
crc size 20
number of chars 12
block size 92
symbol period 30.000
number of symbols 1792
list length 20000000
start offset 1660.000
freq offset 0.000000
cores 1
skipped 1660.178234 seconds to start
initial reference phase -10.0
---------------------------------------------
found 73 TO RUSSIA
list rank 898759
reference phase 0 0 0 0
carrier S/N 18.08 dB in 18.6 uHz, -29.23 dB in 1Hz, -63.21 dB in 2.5kHz
carrier Es/N0 -14.46 dB
carrier Eb/N0 -0.27 dB
info bit period 785.96 seconds
symbol error rate 720/1792 = 40.179 %
Es/N0 from symbol errors -15.0 dB
Eb/N0 from symbol errors -0.8 dB
Shannon capacity 6.1 bits/hour
Shannon efficiency 75.1 %
symbols file C:\EbNaut\DK7FC-12ch-5170\sum_dk7fc — копия-symbols.csv
elapsed 159 seconds

PS My grabber was restarted and now is running on 4470.1 Hz and 8270.1 Hz (with corrected settings)

73 de Alex/rn3aus


Понедельник, 15 января 2018, 23:22 +03:00 от DK7FC <[email protected]>:

17 transmissions completed. Now i stopped transmitting and will QSY to 4470 Hz again soon, but this time with 300 mA. Tonite no transmission (rare).

73, Stefan

Am 29.12.2017 16:11, schrieb DK7FC:
From now on i'm trying to pass 12 characters over to near Moscow, despite the failed decode of the 3 char message.
Details:

f = 5170.1000 Hz
Start time: 29.Dec.2017  15:00:00 UTC
Symbol period: 30 s
Characters: 12
CRC bits: 20
Coding 16K21A
Duration: 14:56 [hh:mm]
Antenna current: 300 mA

A challenge for Jacek also, i think.
Maybe even for Riccardo with his new setup?

73, Stefan



Attachment: stack.png
Description: PNG image

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