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Message-ID: <2FA25F9F5AB648A98C2F0C7A96F0D1B2@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <BLU180-W592EF235819BF7FD96E8C3ACF70@phx.gbl> <05b201ced8d7$24e85fe0$6eb91fa0$@comcast.net>
Date: Sun, 3 Nov 2013 23:40:05 -0000
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Subject: LF: Re: RE: Hartmut's Grabber On Last Night...
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Hi Jim yes I think it is a phase effect, the reinforcement/cancellation =
is probably between 2 hop and 3 hop paths. A 16dB fade suggests 20dB or =
so difference in amplitude. I used to reckon on about a 12dB per =
ionospheric hop and less, maybe 6dB, for a sea "bounce" based on signal =
from Joe VO1NA and the Naval station at Newport Corner near Halifax NS. =
Each hop has a maximum range of about 2000km. There are several effects =
around the sunset shadow area that could add to the effect too. Higher =
angles at the ionosphere may penetrate futher before returning giving =
higher attenuation to the higher hop modes.=20

A thumbnail calculation suggests hop3 ampltude of about -23dB below hop =
2 would give a 17dB fade as it goes in and out of phase.

Very much a "hand waving" estimate but a useful empirical guide.

Alan
G3NYK
  ----- Original Message -----=20
  From: hvanesce=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Sunday, November 03, 2013 8:56 PM
  Subject: LF: RE: Hartmut's Grabber On Last Night...


  Bob,

  =20

  This is the third time that I've noticed Dex's signal peaking =
substantially (>15dB?) starting around 0500, at approximately the same =
time that your signal begins a substantial fade. I've seen this twice on =
captures from Hartmut's grabber, and once on a capture from Mike's =
grabber.=20

  =20

  An interesting example is 21 October 2013, when captures by Henny, =
Mike and Hartmut all showed a fade of roughly 10-15dB in your signal =
from 0500-0530, with Mike's grabber (which showed Dex's signal clearly =
around that time) showing a rise in Dex's signal of roughly 10-15dB. =20

  =20

  I wonder if this could be attributable to modal phase =
reinforcement/cancellation near the terminator? The relative change =
between your signal and Dex's seems rather high for that mechanism, but =
I suppose not out of the question. AGARD CP 305 includes a paper =
(Morfitt) with some interesting plots in this context, and a number of =
other papers with interesting propagation studies at frequencies near =
74kHz; is there a good place for me to post info of this type?

  =20

  73,

  =20

  Jim AA5BW=20

  =20

  From: owner-rsgb_lf_group@blacksheep.org =
[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Bob Raide
  Sent: Sunday, November 3, 2013 12:07 PM
  To: rsgb_lf_group@blacksheep.org
  Subject: LF: Hartmut's Grabber On Last Night...

  =20

  Good shots of Me and Dex-Bob WG2XRS/4 NY [XRS4] and [XRS5]...=20

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<DIV><FONT size=3D2 face=3DArial>Hi Jim yes I think it is a phase =
effect, the=20
reinforcement/cancellation is probably between 2 hop and 3 hop paths. A =
16dB=20
fade suggests 20dB or so difference in amplitude. I used to reckon on =
about a=20
12dB per ionospheric hop and less, maybe 6dB, for a sea "bounce" based =
on signal=20
from Joe VO1NA and the Naval station at Newport Corner near Halifax NS. =
Each hop=20
has a maximum range of about 2000km. There are several effects around =
the sunset=20
shadow area that&nbsp;could add to the effect too. Higher angles at the=20
ionosphere may penetrate futher before returning giving higher =
attenuation to=20
the higher hop modes.&nbsp;</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>A thumbnail calculation suggests hop3 =
ampltude of=20
about&nbsp;-23dB below hop 2 would give a 17dB fade as it goes in and =
out of=20
phase.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Very much a "hand waving" estimate but =
a useful=20
empirical guide.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Alan</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>G3NYK</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20
dir=3Dltr>
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>From:</B>=20
  <A title=3Dhvanesce@comcast.net =
href=3D"mailto:hvanesce@comcast.net">hvanesce</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Drsgb_lf_group@blacksheep.org=20
  =
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Sunday, November 03, 2013 =
8:56=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: RE: Hartmut's =
Grabber On=20
  Last Night...</DIV>
  <DIV><BR></DIV>
  <DIV class=3DWordSection1>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">Bob,<o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">This=20
  is the third time that I=92ve noticed Dex=92s signal peaking =
substantially=20
  (&gt;15dB?) starting around 0500, at approximately the same time that =
your=20
  signal begins a substantial fade. I=92ve seen this twice on captures =
from=20
  Hartmut=92s grabber, and once on a capture from Mike=92s grabber.=20
  <o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">An=20
  interesting example is 21 October 2013, when captures by Henny, Mike =
and=20
  Hartmut all showed a fade of roughly 10-15dB in your signal from =
0500-0530,=20
  with Mike=92s grabber (which showed Dex=92s signal clearly around that =
time)=20
  showing a rise in Dex=92s signal of roughly 10-15dB.=20
&nbsp;<o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">I=20
  wonder if this could be attributable to modal phase =
reinforcement/cancellation=20
  near the terminator? The relative change between your signal and =
Dex=92s seems=20
  rather high for that mechanism, but I suppose not out of the question. =
AGARD=20
  CP 305 includes a paper (Morfitt) with some interesting plots in this =
context,=20
  and a number of other papers with interesting propagation studies at=20
  frequencies near 74kHz; is there a good place for me to post info of =
this=20
  type?<o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">73,<o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt">Jim=20
  AA5BW <o:p></o:p></SPAN></P>
  <P class=3DMsoNormal><SPAN=20
  style=3D"FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; =
FONT-SIZE: 11pt"><o:p>&nbsp;</o:p></SPAN></P>
  <DIV>
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  <P class=3DMsoNormal><B><SPAN=20
  style=3D"FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: =
10pt">From:</SPAN></B><SPAN=20
  style=3D"FONT-FAMILY: 'Tahoma','sans-serif'; FONT-SIZE: 10pt">=20
  owner-rsgb_lf_group@blacksheep.org =
[mailto:owner-rsgb_lf_group@blacksheep.org]=20
  <B>On Behalf Of </B>Bob Raide<BR><B>Sent:</B> Sunday, November 3, 2013 =
12:07=20
  PM<BR><B>To:</B> rsgb_lf_group@blacksheep.org<BR><B>Subject:</B> LF: =
Hartmut's=20
  Grabber On Last Night...<o:p></o:p></SPAN></P></DIV></DIV>
  <P class=3DMsoNormal><o:p>&nbsp;</o:p></P>
  <DIV>
  <P class=3DMsoNormal><SPAN style=3D"FONT-FAMILY: =
'Calibri','sans-serif'">Good=20
  shots of Me and Dex-Bob WG2XRS/4 NY [XRS4] and [XRS5]...=20
  <o:p></o:p></SPAN></P></DIV></DIV></BLOCKQUOTE></BODY></HTML>

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