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Re: VLF: Using resonance effects of earth-ionosphere for radio experimen

To: [email protected]
Subject: Re: VLF: Using resonance effects of earth-ionosphere for radio experiments
From: DK7FC <[email protected]>
Date: Mon, 23 Oct 2017 16:40:03 +0200
In-reply-to: <[email protected]>
References: <[email protected]> <[email protected]>
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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<[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




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