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Stefan
Short term path enhancement at vhf / uhf has been reported over the years.
Jay W1VD
----- Original Message -----
Sent: 5/3/2018 5:31:09 AM
Subject: Re: ULF: A new band is opened up! 191 km | DL0AO results
Paul, ULF,
There is an interesting unexpected observation: In the night of the
30th, there were strong thunderstorms all over Germany. The noise was
very high of course. But when analysing the carrier for that single day
(from the DL0AO data file), i'm getting a peak SNR of 10.98 dB for a 10
hour carrier starting 01:20 UTC. A 6 hour carrier starting at the same
time produces a similar SNR. That peak is the strongest in 5000 bins.
SNR plot attached. I easily decoded a '*' message with good Eb/N0 and no
false decodes.
I had serious doubts but then Markus got similar results with his
totally different way of data analysis.
Can this be real? Could it be propagation? Could it be that the
lightnings have an effect on the ionosphere to improve reflection
significantly so that this S/N can be reached? You know that 191 km wave
is at about lambda/2 at the height of the ionosphere relative to ground
(at night).
We need more such data. The carrier is now running for more than 1 week
without an interruption and it will continue further... Oh and we need
more thunderstorms on the path! :-)
It would be most interesting to see if you're getting similar results
from the data of DL4YHF, which is a different and longer path.
Another thought: I choose 1.57 kHz because this is below that 'cut-off'
frequency for distant sferic propagation (the distant sferic S/N drops
by say 20 dB at 1.6 kHz at night), so the night QRN is much lower there.
BUT, maybe it would be even better to transmit directly on that cut-off
frequency, i.e. between 1.6...1.65 kHz?! No problem to move to that
frequency but let's collect more data on 1570.01 Hz for the next weeks.
Looks like an ideal summer experiment!
73, Stefan
Am 01.05.2018 15:29, schrieb Paul Nicholson:
>
> So far, nothing at Todmorden, by stacking all the daytime
> signals, or by chaining them for super narrow bandwidth.
>
> Some problems using Bielefeld vlf6, the stream often
> steps backwards one sample at a time and I'm not sure
> where that leaves the phase.
>
> --
> Paul Nicholson
> --
>
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