Hi Stefan,
Actually, 1 - 4 kHz is the worst frequency range as it is right between the two
waveguide Modes 0 and 1.
ELF around 100 Hz is good for Mode 0 and Mode 1 peaks around 15 kHz.
73 John VA3VVV
--------------------------------------------
On Mon, 10/23/17, DK7FC <[email protected]> wrote:
Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio
experiments
To: "[email protected]" <[email protected]>
Received: Monday, October 23, 2017, 9:05 AM
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
|
