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Date: Mon, 23 Oct 2017 15:05:13 +0200
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio experiments
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Hi John,

Thank you.
The large image is well known meanwhile but i did see the other one so 
far. Where did you take it from and are there more informations?
What means ||Tn| ? I guess n is the numer of hops. But T = Tesla? Not 
really. It should be |B(n)|. So maybe something else. But it would make 
sense that is is something that has to do with the field strength. Odd...
Assuming it is actually the fieldstrength, then 1 kHz looks most 
interesting again. I need to continue to work in that range!!

73, Stefan

Am 23.10.2017 14:21, schrieb John Fisher:
> Hi Stefan,
>
> Attached re two graphs on this subject you might find interesting.
>
> 73 John VA3VVV
>
>
>
> --------------------------------------------
> On Mon, 10/23/17, DK7FC<selberdenken@posteo.de>  wrote:
>
>   Subject: VLF: Using resonance effects of earth-ionosphere for radio experiments
>   To: rsgb_lf_group@blacksheep.org
>   Received: Monday, October 23, 2017, 7:15 AM
>
>   Paul, Markus, VLF,
>
>   Some days ago there have been
>   local thunderstorms near DL0AO in JN59.
>   Two
>   images in attachemnt.
>   The distance is about
>   225 km. The thunderstorms were on a small spot only.
>
>   The sferics are clearly
>   pronounced with an SNR increase of 10 dB and
>   more, quite a sharp peak/trace. That's not
>   a new observation but now we
>   are operating
>   just in that frequency range!
>   The effect
>   seems to appear in integer multiples of about 1.7 kHz, which
>
>   is roughly a wavelength of a 180 km, and
>   the earth-ionosphere height is
>   just
>   lambda/2.
>
>   It would be most
>   interesting to see how a similar spectrogram looks from
>   Pauls site (time and date given in the images).
>   Is the effect still
>   there in 881 km? How
>   strong is it expressed. Are the frequencies the same?
>   If so, we should try to find that region of
>   enhanced propagation, by
>   using a 2-tone or
>   3-tone carrier signal. No problem to provide that from
>   here.
>
>   The
>   effect is less expressed on 3.4 kHz in this event. Recently
>   we
>   discussed about a geometric single-hop
>   path difference between DK7FC and
>   DL0AO
>   (Markus calculated 63.3 km difference between groundwave and
>
>   skywave). 5.17 is at a 1.09 lambda
>   difference on that path, so
>   groundwave and
>   skywave will add constructively. The 3rd order trace of
>   the sferic resonance effect is also at 5.1
>   kHz!
>   3.4 kHz, or the 88.2 km wave, is then
>   at 1.4 lambda difference, so
>   skyway and
>   groundwave do not add so constructive. Maybe this explains
>
>   the lower expressed resonance effect?
>
>   It looks like there can be SNR
>   difference of several dB when changing
>   the
>   frequency by just a few 10 Hz, at least arround 5.1 kHz and
>   on the
>   path to DL0AO. We should try to
>   check that!
>
>   Could there be
>   a frequency with an advantage on the way to RN3AUS? On a
>   2000 km path the effects will be less
>   expressed. But worth to think about...
>
>   73, Stefan