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Date: Mon, 23 Oct 2017 16:40:03 +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,

Yes, like on HF it is a different league to work on 15 kHz or 8.27 kHz 
or 2.97 kHz. Working VK from DL in SSB is usually easier on 20m than on 
80m, same for WSPR of course. So one may ask "Why are you trying to work 
VK on 80m, 20m is much easier?!"
Some youngsters may even ask "Why are you using radio at all, there is 
skype!!?!" :-)

73, Stefan

Am 23.10.2017 16:17, schrieb John Fisher:
> 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<selberdenken@posteo.de>  wrote:
>
>   Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio experiments
>   To: "rsgb_lf_group@blacksheep.org"<rsgb_lf_group@blacksheep.org>
>   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<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
>
>
>
>