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Message-ID: <7955E8B83E254BA282A4BF6ECDCFFA18@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <BLU153-W7B8F81140FFCE4ED08C28CFDD0@phx.gbl>
Date: Tue, 24 Jul 2012 00:48:51 +0100
MIME-Version: 1.0
Subject: LF: Re: Chaff and LF
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Hi Laurence, I didnt thinkanything as crude as "chaff"was used in ECM =
these days :-))
A couple of thoughts..... it was probably dropped from 30000ft altitude =
10km. the effective path length for reflection off that would be quite =
short around the same as VHF and microwave aircraft scatter. This has a =
rangel limited to arounf 700milesmax (I think some of that isdue to =
tropo bending too, which is not available at LF=20

The original "chaff" was cut to half wavelengths but that was when radar =
was using vhf/uhf. At LF the effect would probably be one of scattering. =
I think the cross-section of a jumbo even, at 136khz would be quite =
small. Geo effects tend to make man's efforts look a bit puny :-))

Alan
  ----- Original Message -----=20
  From: Laurence KL7UK=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Monday, July 23, 2012 10:45 PM
  Subject: LF: Chaff and LF



  One of the most interesting weather reports this week was from Hawaii =
- when a radar image showed a broad swarth of radar returns some 15 =
miles long and 1 mile wide gradually moving South with the prevailing =
wind. I first thought it was a a weather gust front or rain squal but =
the weather chappy says it was from the ongoing military exercises and =
they had dropped a large amount of the chaff stuff (radar =
sized/reflective) and it was causing the X band radar to show it in =
detail.=20
  =20
  I was pondering - as I sat on the beach on Maui the next day whether =
this form of chaff can actually produces anomolies below the frequency =
engineered - as a lot of the new type of chaff has to cover a load of =
GHz and MHz channelling - if the area is large enough, as this was, and =
the drop density of reflective material is large enough whether it would =
cause some effects as it appeared to be dropped from 30,000ft or =
so...even down to LF...?
  =20
  Another anomoly was seen this morning when I was returning from =
Honolulu back to Anchorage - I was approx 1200 miles South of Anchorage =
and a Blue glow started to appear - firstly I thought it was just a band =
of Green/Blue Auroral light we get fairly often but  as we got closer it =
was the Notchtilucent clouds way way above us - banded, stripes and =
globs of thin cloud being illuminated by the sun which was way below our =
horizon and actually not even a pre glow. Now - this isnt a normal radio =
thing either but on reading up on these clouds it appears they too are =
radio reflective up to a point given the ions that attach to the =
nulceous and given they appear to be sub-polar or polar, and mostly a =
summer thing, when the temps are coldest at that altitude Im wondering =
if some of the oddities we see on MF and HF are caused by these clouds =
too...
  =20
  =20

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<DIV><FONT face=3DArial>Hi Laurence, I didnt thinkanything as crude as =
"chaff"was=20
used in ECM these days :-))</FONT></DIV>
<DIV><FONT face=3DArial>A couple of thoughts..... it was probably =
dropped from=20
30000ft altitude 10km. the effective path length for reflection off that =
would=20
be quite short around the same as VHF and microwave aircraft scatter. =
This has a=20
rangel limited to arounf 700milesmax (I think some of that isdue to =
tropo=20
bending too, which is not available at LF&nbsp;</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>The original "chaff" was cut to half wavelengths =
but that=20
was when radar was using vhf/uhf. At&nbsp;LF the effect would probably =
be one of=20
scattering. I think the cross-section of a jumbo even, at 136khz would =
be quite=20
small. Geo effects tend to make man's efforts look a bit puny =
:-))</FONT></DIV>
<DIV><FONT face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial>Alan</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=3Dhellozerohellozero@hotmail.com=20
  href=3D"mailto:hellozerohellozero@hotmail.com">Laurence KL7UK</A> =
</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> Monday, July 23, 2012 =
10:45=20
PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: Chaff and LF</DIV>
  <DIV><BR></DIV>
  <DIV dir=3Dltr><BR>One of the most interesting weather reports this =
week was=20
  from Hawaii - when a radar image showed a broad swarth of radar =
returns some=20
  15 miles long and 1 mile wide gradually moving South with the =
prevailing wind.=20
  I first thought it was a a weather gust front or rain squal but the =
weather=20
  chappy says it was from the ongoing military exercises and they had =
dropped a=20
  large amount of the chaff&nbsp;stuff (radar sized/reflective) and it =
was=20
  causing the X band radar to show it in detail. <BR>&nbsp;<BR>I was =
pondering -=20
  as I sat on the beach on Maui the next day whether this form of chaff =
can=20
  actually produces anomolies below the frequency engineered - as a lot =
of the=20
  new type of chaff has to cover a load of GHz and MHz channelling - if =
the area=20
  is large enough, as this was, and the drop density of reflective =
material is=20
  large enough whether it would cause some effects as it appeared to be =
dropped=20
  from 30,000ft or so...even down to LF...?<BR>&nbsp;<BR>Another anomoly =
was=20
  seen this morning when I was returning from Honolulu back to Anchorage =
- I was=20
  approx 1200 miles South of Anchorage and a Blue glow started to appear =
-=20
  firstly I thought it was just a band of Green/Blue Auroral light we =
get fairly=20
  often but&nbsp; as we got closer it was the Notchtilucent clouds way =
way above=20
  us - banded, stripes and globs of thin cloud being illuminated by the =
sun=20
  which was way below our horizon and actually not even a pre glow. Now =
- this=20
  isnt a normal radio thing either but on reading up on these clouds it =
appears=20
  they too are radio reflective up to a point given the ions that attach =
to the=20
  nulceous and given they appear to be sub-polar or polar, and mostly a =
summer=20
  thing, when the temps are coldest at that altitude Im wondering if =
some of the=20
  oddities we see on MF and HF are caused by these clouds=20
  too...<BR>&nbsp;<BR>&nbsp;<BR></DIV></BLOCKQUOTE></BODY></HTML>

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