Re: VLF: Finally back on the 58 km band...

[Markus Vester <markusvester@aol.com>]

Hi Stefan

as a "local" crosscheck, I had a look at your 3-character transmissions from DL0AO.  Here are carrier Eb/N0 and "initial reference phase" from the EbNaut decoder's log files:

Files 5k17W_12dd2252.txt  (21 uHz)
Offset 0.05 Hz -2674 s (94% covered)

date dB deg

23  9.1  34.4
24  8.8  30.8
25  6.9  25.3
26  9.1  47.4
27  9.5  86.1

Apparently received EbNaut phase was somewhat different during the last two nights. On the other hand, the phase plot on the grabber shows that the daytime carrier had a repeatable phase pattern. If you like to check for yourself, I could send zipped txt files in a private email.

Best 73,
Markus




-----Ursprüngliche Mitteilung-----
Von: DK7FC <selberdenken@posteo.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Do, 28. Dez 2017 18:53
Betreff: Re: VLF: Finally back on the 58 km band...

Hello Alex,

Thanks for the reception and the files.
Unfortunately the message is not correct.
I analysed your files and found the message at:

23rd: -8.0 dB
24th: -5.0 dB
25th: -6.2 dB
26th: -10.0 dB
27th: -16.2 dB

23+24: -3.6 dB
23+24+25: -1.7 dB
23+24+25+26: -1.4 dB
23+24+25+26+27: -2.1 dB

It looks like something happened on the 27th. The noise has not really been higher than average but the message is quite down in the noise.
Hmm, maybe there was some snow on the GPS antenna for example? It could have happend during the transmission of the 26th, this could explain why the signal is so weak. Or something happened with the antenna?
When trying to get a decode from 23+24+25+26 only, the right message appears at rank 648. But there are several other stronger messages here. Also this (that 23-26 is better than 23-27) is known information, thus the decode would not be valid.

So we are almost there but we failed :-(

So maybe you are right, maybe a restart is a good decision. On the other side, you will loose all messages that are started for now, the message from Dex and so on.
In the end it is your decision...
It may be worth to check if the antenna+preamp is still working.

73, Stefan


Am 28.12.2017 16:58, schrieb Alex K:

Hello Stefan, VLF!

The files from all 5 nights are here:
http://rn3aus.narod.ru/DK7FC-3char.zip 

Stacking procedure give me decode "AVP":   (Hmmm...)

ebnaut-rx V0.7a
input file C:\EbNaut\VLF_EBNAUT\DK7FC-3char-dec2017\sum.wav
sample rate 0.342935 per second
rx frequency 5170.1
file start time 2017-12-27 15:31:11.790
polynomial 16K21A
crc size 11
number of chars 3
block size 29
symbol period 60.000
number of symbols 784
list length 2000
start offset -58.400
freq offset 0.000000
cores 1
padded 58.320 seconds at start
initial reference phase -7.4
---------------------------------------------
found AVP
list rank 286
reference phase 30 30 30 30
carrier S/N 11.72 dB in 21.3 uHz, -35.00 dB in 1Hz, -68.98 dB in 2.5kHz
carrier Es/N0 -17.22 dB
carrier Eb/N0 -0.61 dB
info bit period 2750.88 seconds
symbol error rate 328/784 = 41.837 %
Es/N0 from symbol errors -16.7 dB
Eb/N0 from symbol errors -0.1 dB
Shannon capacity 1.6 bits/hour
Shannon efficiency 80.5 %
symbols file C:\EbNaut\VLF_EBNAUT\DK7FC-3char-dec2017\sum-symbols.csv
elapsed 33 seconds
---------------------------------------------
found AVP
list rank 144
reference phase 60 60 30 30
carrier S/N 11.98 dB in 21.3 uHz, -34.75 dB in 1Hz, -68.73 dB in 2.5kHz
carrier Es/N0 -16.97 dB
carrier Eb/N0 -0.35 dB
info bit period 2750.88 seconds
symbol error rate 333/784 = 42.474 %
Es/N0 from symbol errors -17.4 dB
Eb/N0 from symbol errors -0.8 dB
Shannon capacity 1.7 bits/hour
Shannon efficiency 75.9 %
symbols file C:\EbNaut\VLF_EBNAUT\DK7FC-3char-dec2017\sum-symbols.csv
elapsed 164 seconds
---------------------------------------------
found AVP
list rank 196
reference phase 60 30 30 0
carrier S/N 11.98 dB in 21.3 uHz, -34.75 dB in 1Hz, -68.73 dB in 2.5kHz
carrier Es/N0 -16.97 dB
carrier Eb/N0 -0.35 dB
info bit period 2750.88 seconds
symbol error rate 336/784 = 42.857 %
Es/N0 from symbol errors -17.9 dB
Eb/N0 from symbol errors -1.3 dB
Shannon capacity 1.7 bits/hour
Shannon efficiency 75.9 %
symbols file C:\EbNaut\VLF_EBNAUT\DK7FC-3char-dec2017\sum-symbols.csv
elapsed 535 seconds

I can also visit my grabber tmr ( Friday). I think the grabber need restart for stable operation on the holiday. Unfortunately (fortunately :) ) I will to 9 Jan 2018 in the little holiday trip with my family so next visit to the grabber is planned to 10 Jan.

73 de rn3aus/Alex

Четверг, 28 декабря 2017, 13:49 +03:00 от DK7FC <selberdenken@posteo.de>:

5 transmissions are completed now. I expect this is enough to leave a clear decode at RN3AUS.
Alex' txt files will be invaluable this time :-) They may contain the messages of VO1NA, W4DEX as well as my litte contribution on 5170 Hz over the negligible distance of 1985 km :-)

Without having the confirmation of a successful message decode i'm announcing and starting the next message this evening. This will take a while to decode near Moscow. It can be a challenge of the other VLF receivers in the region:

f = 5170.1000 Hz
Start time: 28.Dec.2017  15:30:00 UTC (daily)
Symbol period: 30 s
Characters: 12
CRC bits: 6
Coding 16K21A
Duration: 13:04 [hh:mm]
Antenna current: 300 mA

73, Stefan


Am 23.12.2017 01:32, schrieb DK7FC:

VLF,

It feels good to be back on the well audible frequencies. Finally i'm running a carrier on 5170.005 Hz again, since 21:30 UTC. The target antenna current is 300 mA, the actual level is arround 260 mA at present.
The carrier will run until my next EbNaut message will start tomorrow!
In October Alex and me managed to pass 1 character on 5170 Hz over the almost 2000 km land path, a record distance on that band. Now the next challenge is to try 3 characters. Since the nights are long, we can use very long transmission times. However i think the FFT window length at RN3AUS is currently just 13.27 hours so i try:

f = 5170.1000 Hz
Start time: 23.Dec.2017  15:30:00 UTC (daily)
Symbol period: 60 s
Characters: 3
CRC bits: 11
Coding 16K21A
Duration: 13:04 [hh:mm]
Antenna current: 300 mA


73, Stefan