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From: "Dave G3WCB" <ganymede444@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
Date: Sun, 29 Apr 2007 10:47:56 +0100
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Subject: LF: RE: 500 Loops (was PA2NL)
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Hi, Laurie, LF.

I use a tuned loop for Rx on 136 kHz, and it is also affected by the TX
"Tee" antenna. I use a relay to open circuit the earth return at the bottom
of the TX antenna ATU  when the loop is in use. The problem isn't due to the
presence of the TX antenna wire itself, but the problems occur when the wire
is resonated by the TX ATU. The TX ATU earth has a 1 meg bleed resistor left
in circuit to leak away any static build up.

73, Dave G3WCB IO91RM
  -----Original Message-----
  From: owner-rsgb_lf_group@blacksheep.org
[mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of lawrence mayhead
  Sent: 29 April 2007 10:20
  To: rsgb
  Subject: LF: 500 PA2NL QRS


  PA2 beacon very strong here also, on the south coast.

  Interesting antenna effect:-
  I run a pair of large grounded loops situated close to the main TX antenna
(inv L )
  These have worked very well on 136 and are quite directional, providing
useful
  improvement in SNR. On 500kHz however they are not directional, at least
not
  in the right directions.
  I have spent several hours trying to find out what has gone wrong with
them !
  By chance this morning I left the TX ant. grounded and was surprised to
find that
  the loops are now directional. So it looks like there is much more
coupling between the
  TX and RX ants on 500 than 136.
  Could this simply be capacitive ? perhaps I need smaller loops?
  Anyway if you are running a RX loop close to your TX antenna, beware.
  73 Laurie.

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charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.2800.1458" name=3DGENERATOR></HEAD>
<BODY>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><SPAN =
class=3D293523509-29042007>Hi,=20
Laurie, LF.</SPAN></FONT></DIV>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><SPAN=20
class=3D293523509-29042007></SPAN></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><SPAN =
class=3D293523509-29042007>I use=20
a tuned loop for Rx on 136 kHz, and it is also affected by the TX "Tee" =
antenna.=20
I use a relay to open circuit the earth return at the bottom of the TX=20
antenna&nbsp;ATU&nbsp;&nbsp;when the loop is in use. The =
problem&nbsp;isn't due=20
to the presence of the TX antenna wire itself, but&nbsp;the problems =
occur when=20
the wire is resonated by the TX ATU. The TX&nbsp;ATU earth&nbsp;has a 1 =
meg=20
bleed resistor left in circuit to leak away any static build=20
up.&nbsp;</SPAN></FONT></DIV>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><SPAN=20
class=3D293523509-29042007></SPAN></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial color=3D#0000ff size=3D2><SPAN =
class=3D293523509-29042007>73,=20
Dave G3WCB IO91RM</SPAN></FONT></DIV>
<BLOCKQUOTE>
  <DIV class=3DOutlookMessageHeader dir=3Dltr align=3Dleft><FONT =
face=3DTahoma=20
  size=3D2>-----Original Message-----<BR><B>From:</B>=20
  owner-rsgb_lf_group@blacksheep.org=20
  [mailto:owner-rsgb_lf_group@blacksheep.org]<B>On Behalf Of =
</B>lawrence=20
  mayhead<BR><B>Sent:</B> 29 April 2007 10:20<BR><B>To:</B>=20
  rsgb<BR><B>Subject:</B> LF: 500 PA2NL QRS<BR><BR></FONT></DIV>PA2 =
beacon very=20
  strong here also, on the south coast.<BR><BR>Interesting antenna =
effect:-<BR>I=20
  run a pair of large grounded loops situated close to the main TX =
antenna (inv=20
  L )<BR>These have worked very well on 136 and are quite directional, =
providing=20
  useful<BR>improvement in SNR. On 500kHz however they are not =
directional, at=20
  least not<BR>in the right directions.<BR>I have spent several hours =
trying to=20
  find out what has gone wrong with them !<BR>By chance this morning I =
left the=20
  TX ant. grounded and was surprised to find that<BR>the loops are now=20
  directional. So it looks like there is much more coupling between =
the<BR>TX=20
  and RX ants on 500 than 136.<BR>Could this simply be capacitive ? =
perhaps I=20
  need smaller loops?<BR>Anyway if you are running a RX loop close to =
your TX=20
  antenna, beware.<BR>73 Laurie.<BR></BLOCKQUOTE></BODY></HTML>

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