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From: Markus Vester <markusvester@aol.com>
Message-Id: <8D061903E9F3B4C-8C4-6E59@webmail-d279.sysops.aol.com>
Date: Wed, 7 Aug 2013 10:19:21 -0400 (EDT)
Subject: Re: LF: VLF strange pattern
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... rethinking my reply: multiple-hop tweek formation=C2=A0may not be requi=
red to explain the bands. Even=C2=A0a simple superposition of groundwave an=
d a single ionospheric reflection=C2=A0will create this type=C2=A0of interf=
erence pattern, as long as spherics from a reasonably similar range are inv=
olved.
=C2=A0
Best 73,
Markus

=C2=A0


-----Urspr=C3=BCngliche Mitteilung-----=20
Von: Markus Vester &lt;markusvester@aol.com&gt;
An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;
Verschickt: Mi, 7 Aug 2013 3:58 pm
Betreff: Re: LF: VLF strange pattern

Stefan,

the banded spectral structure=C2=A0could be due to=C2=A0multiple bounces be=
tween the ionosphere and ground. Under favourable conditions,=C2=A0consecut=
ive=C2=A0steeper and steeper reflections can produce a "tweek",=C2=A0ie a=
=C2=A0pulsetrain with decreasing repetition rate.=C2=A0During the tail, the=
re are distinct spectral maxima about 1.7 kHz apart, defined by the delay f=
or near vertical travel=C2=A0to the D-layer and down again. Tweek formation=
 would be favoured by high-altitude horizontal lightning,=C2=A0good ground =
reflectivity (water), and a steep=C2=A0ionization gradient at the bottom of=
 the ionosphere at night.
=C2=A0
As the phasing somewhat depends on the ground distance between the strike a=
nd the receiver,=C2=A0patterns from spatially extended storm areas may=C2=
=A0average out in a slow spectrogram, unless the lightning=C2=A0activity is=
 concentrated in a small area or ring around the receiver. Attached is a pl=
ot from the Blitzortung archive from 1 to 3 UT.=C2=A0We could speculate tha=
t the region of activity=C2=A0in Western France was creating your tweeks an=
d the Polish "arc" was responsible for Lubos', but it's hard to tell for su=
re.
=C2=A0
Best 73,
Markus (DF6NM)
=C2=A0
=C2=A0


-----Urspr=C3=BCngliche Mitteilung-----=20
Von: Stefan Sch=C3=A4fer &lt;Stefan.Schaefer@iup.uni-heidelberg.de&gt;
An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;
Verschickt: Mi, 7 Aug 2013 2:28 pm
Betreff: LF: VLF strange pattern


VLF,=20
 =20
 Just discovered a strange QRN pattern on VLF this night. See attachment. =
=20
 The origin cannot be local because the same was shown on the OK2BVG VLF =
=20
 grabber.=20
 What is it?=20
 =20
 73, Stefan/DK7FC=20
=20


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<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><FONT colo=
r=3Dblack face=3Darial>... rethinking my reply: multiple-hop tweek formatio=
n&nbsp;may not be required to explain the bands. Even&nbsp;a simple superpo=
sition of groundwave and a single ionospheric reflection&nbsp;will create t=
his type&nbsp;of interference pattern, as long as spherics from a reasonabl=
y similar range are involved.</FONT></div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Best 73,</=
div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Markus</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><br>
&nbsp;</div>


<div><br>
</div>
-----Urspr=C3=BCngliche Mitteilung----- <br>
Von: Markus Vester &lt;markusvester@aol.com&gt;<br>
An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;<br>
Verschickt: Mi, 7 Aug 2013 3:58 pm<br>
Betreff: Re: LF: VLF strange pattern<br>
<br>


<div id=3DAOLMsgPart_2_219b89d5-7656-4423-af21-67b83b38ae9f>

<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><FONT colo=
r=3Dblack face=3Darial>Stefan,</FONT></div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt"><SPAN styl=
e=3D"DISPLAY: inline-block"></SPAN></div>


<div>the banded spectral structure&nbsp;could be due to&nbsp;multiple bounc=
es between the ionosphere and ground. Under favourable conditions,&nbsp;con=
secutive&nbsp;steeper and steeper reflections can produce a "tweek",&nbsp;i=
e a&nbsp;pulsetrain with decreasing repetition rate.&nbsp;During the tail, =
there are distinct spectral maxima about 1.7 kHz apart, defined by the dela=
y for near vertical travel&nbsp;to the D-layer and down again. Tweek format=
ion would be favoured by high-altitude horizontal lightning,&nbsp;good grou=
nd reflectivity (water), and a steep&nbsp;ionization gradient at the bottom=
 of the ionosphere at night.</div>


<div>&nbsp;</div>


<div>As the phasing somewhat depends on the ground distance between the str=
ike and the receiver,&nbsp;patterns from spatially extended storm areas may=
&nbsp;average out in a slow spectrogram, unless the lightning&nbsp;activity=
 is concentrated in a small area or ring around the receiver. Attached is a=
 plot from the Blitzortung archive from 1 to 3 UT.&nbsp;We could speculate =
that the region of activity&nbsp;in Western France was creating your tweeks=
 and the Polish "arc" was responsible for Lubos', but it's hard to tell for=
 sure.</div>


<div>&nbsp;</div>


<div>Best 73,</div>


<div>Markus (DF6NM)</div>


<div>&nbsp;</div>


<div>&nbsp;</div>


<div><br>
</div>
-----Urspr=C3=BCngliche Mitteilung----- <br>
Von: Stefan Sch=C3=A4fer &lt;<A href=3D"mailto:Stefan.Schaefer@iup.uni-heid=
elberg.de">Stefan.Schaefer@iup.uni-heidelberg.de</A>&gt;<br>
An: rsgb_lf_group &lt;<A href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_=
lf_group@blacksheep.org</A>&gt;<br>
Verschickt: Mi, 7 Aug 2013 2:28 pm<br>
Betreff: LF: VLF strange pattern<br>


<div style=3D"BACKGROUND-COLOR: #fff; MARGIN: 0px; FONT-FAMILY: Tahoma, Ver=
dana, Arial, Sans-Serif; COLOR: #000; FONT-SIZE: 12px" id=3Daolmail_AOLMsgP=
art_0_f39d5fe7-645a-40b3-9c6c-cc5077a61a63><br>
<br>
<PRE style=3D"FONT-SIZE: 9pt"><TT>VLF, <br>
  <br>
 Just discovered a strange QRN pattern on VLF this night. See attachment.  =
<br>
 The origin cannot be local because the same was shown on the OK2BVG VLF  <=
br>
 grabber. <br>
 What is it? <br>
  <br>
 73, Stefan/DK7FC <br>
 </TT></PRE><br>
</div>
<br>
</div>

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