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<[email protected]> wrote:
Subject: VLF: Using resonance effects of earth-ionosphere for radio
experiments
To: [email protected]
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
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