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