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Date: Fri, 04 Nov 2016 15:05:48 +0100
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Subject: Re: VLF: EbNaut transmissions on lower frequencies?, pre-tests: 6.47kHz
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Paul,

Thanks for the results. BUT! Another idea:

You know the mode "WOLF", used on LF years ago and rarely these days 
(maybe someone will use it again now? :-) ).

A message is sent several times and the sequences are added until a 
decode appears. (Sorry for the bad formulation).

Couldn't we do that the same way on VLF?
In SpecLab i'm steering the PA and PSK and Start/Stop times of the 
carrier directly, in the periodic actions. See 
https://dl.dropboxusercontent.com/u/19882028/VLF/EbNaut_SL.png
At 5 UTC (when i am deeply sleeping) the TX starts and warms up the 
coil. At 6 UTC the message / PSK keying is started. At 20:08 UTC the 
carrier / transmission is stopped after the end of the last symbol.

This procedure is repeated day by day, endlessly, or, until the electric 
bill arrives.
I could just run it for another day and you can build an overlay of the 
two transmissions, right?

This is a different thing then, a different league compared to 
single/'normal' EbNaut transmissions.

Would you agree that this makes sense? If so, i would repeat the message 
just like the first one that did not decode so far, as you say. If this 
will work, we could even think about shorter symbol periods to 
concentrate on the low QRN periods.

73, Stefan


Am 04.11.2016 14:44, schrieb Paul Nicholson:
>
> > Start time: 03.11.2016   06:00:00 UTC
> > Symbol length: 30 s
> > Characters: 11
>
> No decode of this one.
>
> > Time for a night-transmission test!
>
> Let's try.
>
> > Did you ever see a frequency offset or (relevant) time
> > offset on my transmissions.
>
> Frequency ok, carrier and successful decodes showed no
> phase shift over long periods.  Signal too weak to check
> for short period phase changes.
>
> I haven't looked to bit clock offsets, I assume with these
> long symbols that it won't be a problem.
>
> > There are short periods in which the error density is
> > very high,
>
> Eg 13:30 to 14:30 but the noise was low.  And there are
> short periods when it is completely red.  Even random
> noise would only give half red.  Probably just statistics.
>
> > It's a bit a pity that the phase varies so much between
> > day and night.
>
> No so much, 60 degrees, and I can compensate for that before
> the decoder.   Day/night phase change should be less of a
> problem as we go to lower frequencies.  LWPC is not much
> help without a better ionosphere model than its basic
> LWPM model.
>
> -- 
> Paul Nicholson
> -- 
>
>