R: Re: VLF: EbNaut 3 character attempt to VK7

["marcocadeddu@tin.it" <marcocadeddu@tin.it>]

just one :-)
keep on with your patience and dedication, you will get the resoult! :-)
73, Marco IK1HSS


----Messaggio originale----
Da: selberdenken@posteo.de
Data: 26-set-2018 9.08
A: <rsgb_lf_group@blacksheep.org>
Ogg: Re: VLF: EbNaut 3 character attempt to VK7





Here is an update on the ongoing experiment between Edgar and me,
trying to pass a 3 character EbNaut message over to VK7 on 17.4701 kHz.

Since the 21st September i'm transmitting the same message with
identical parameters, one starts at 16:30 UTC, the other one at 19:30
UTC.
After some days it showed that the first time slot does not develop
positively (2 days = +3 dB, 4 days = +6 dB....). The second message was
more promising. After 3 days stacked it got up to 9.71 dB SNR.
Best result so far:
rank 2673527 ber 4.5833e-01 Eb/N0 -5.3 M -6.947182617e+02 ph 77
150,180,150,180
But this is not really a valid decode because you only get it when
knowing the message before and searching explicitely for it.
Yesterday i got the 4th file, today the 5th.
Adding the 4th and 5th file to the stack unfortunately lowers the SNR
again.

What now? 
There is something to try:
These days the sunset happens about 2 minutes per day earlier. I want
to try if it helps to start the transmission 2 minutes earlier per day.
Of course this must be considered / compensated when building the stack.
So now i'm continuing to transmit the same messages but the start times
will be:
26th: 16:28 and 19:28 UTC
27th: 16:26 and 19:26 UTC
28th: 16:24 and 19:24 UTC

and so on...

We have not been to far away from a valid decode, so let's hope this
will help.

Comments or ideas?

73, Stefan


Am 20.09.2018 21:12, schrieb DK7FC:
>   
> Correction: Same parameters as used for the first message, i.e. both
> messages use 
>   
>   f = 17470.1000 Hz
> Start time: 20.SEP.2018  19:30:00 UTC & 16:30:00 UTC (daily)
> Symbol period: 10 s
> Characters: 3
> CRC bits: 19
> Coding 16K21A
> Antenna current: 1.2 A
>   
> 73, Stefan
>   
>   
> Am 20.09.2018 21:02, schrieb DK7FC:
> >     
> > VLF, 
> >     
> > In addition to the message below, which has been transmitted 3 times
> > already, i will start to transmit the same message into a later time
> > slot, also using different parameters:
> >     
> >     f = 17470.1000 Hz
> > Start time: 20.SEP.2018  19:30:00 UTC (daily)
> > Symbol period: 10 s
> > Characters: 3
> > CRC bits: 16
> > Coding 16K21A
> > Duration: 02:24 [hh:mm] 
> > Antenna current: 1.2 A
> >     
> >     73, Stefan
> >     
> > Am 17.09.2018 16:14, schrieb DK7FC:
> > >       
> > > Edgar, VLF, 
> > >       
> > > After evaluating the latest 4 days of carrier transmissions it shows
> > > that the path from DL to VK7 is quite unstable, i.e. the phase is very
> > > dynamic.  When applying different frequency offsets, it seems that the
> > > best start time for a message attempt is 16:30 UTC these days. The SNR
> > > then peaks when applying a -40 uHz offset, attached. Something between
> > > 2...3 hours seems to be best. Currently 2 hours seem to give better
> > > results but 3 hours would be less dynamic.
> > > Based on this data i'm trying:
> > >       
> > >       f = 17470.1000 Hz
> > > Start time: 17.SEP.2018  16:30:00 UTC (daily)
> > > Symbol period: 10 s
> > > Characters: 3
> > > CRC bits: 19
> > > Coding 16K21A
> > > Duration: 02:32 [hh:mm] 
> > > Antenna current: 1.2 A
> > >       
> > > 73, Stefan
> > >     
> >