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Message-ID: <9BE105EBAA5D429D8A7C1F8AE8B2FB65@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <7E7DFBB4D102A04DB5ADC88D66628A4A0FC908D5@ICTS-S-MBX2.luna.kuleuven.be>,<527CEE11.8070509@iup.uni-heidelberg.de> <7E7DFBB4D102A04DB5ADC88D66628A4A0FC98037@ICTS-S-MBX1.luna.kuleuven.be> <527D0CCB.6090208@iup.uni-heidelberg.de> <527D300A.7000909@aol.com> <527D3331.7080109@iup.uni-heidelberg.de>
Date: Fri, 8 Nov 2013 19:35:09 -0000
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Subject: Re: LF: remote antenna tuning
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Rik, Stefan, I follow your points but there would seem to be something =
strange in Rik's antenna or his appreciation of what/how its working.=20

Contrary to an earlier assertion, the antenna current flowing through =
Rrad generates the radiated power, so lower current, if Rrad doesnt =
change, MUST mean lower tranmitted power. It matters not that the SWR is =
unity. A unity SWR indication at the transmitter says that the impedance =
at the end of the coax is 50ohms, but it does not necessarily indicate =
the the the antenna is resonant i.e the inherent capacitance of a short =
antenna totally compensated by the loading inductance. If we assume that =
Rrad+Rloss does not change across the band the matching transformer =
should transform the value of Rrad+Rloss to 50 ohms across all the band. =
The coax will now be matched and will present 50ohms at the shack end. =
If this does not happen I would be inclined to suspect currents induced =
in the coax braid. SWR indicators can easily be confused by induced =
braid currents......could this be the cause of Riks strange effects? =
This might be a function of having a "better" ground in the shack than =
at the base of the antenna.

Alan
G3NYK
=20
  ----- Original Message -----=20
  From: Stefan Sch=E4fer=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Friday, November 08, 2013 6:53 PM
  Subject: Re: LF: remote antenna tuning


  Oh yes, or, a phase meter (M0BMU) and a battery operated variometer =
motor. Without an additional cable to the shack. Then the SWR meter in =
the shack confirms that everything is fine.

  73, Stefan

  Am 08.11.2013 19:40, schrieb pat:=20
    Hi All,

    A suggestion: battery operated tuning device at antenna end and =
"wireless" link back to shack. Wireless can operate at a non-interfering =
frequncy (HF/VHF/UHF/Optical).

    73


    On 08/11/13 16:09, Stefan Sch=E4fer wrote:

      Hi Rik,

      Am 08.11.2013 16:06, schrieb Rik Strobbe:=20
        Hi Stefan,


        remote tuning of the loading should be done by optimizing SWR =
(at the TX), not for maximum RF current.

        If one keeps that in mind there is no problem.

      ...which is in agreement with what i said.
      But once you have matched your antenna to 50 Ohm on resonance and =
you can only vary the reactive part of the antennas impedance (after =
doing QSY), then you will get the maximum antenna current at best SWR =
(assuming that Rrad+Rloss is constant which is not to far from reality).


        I am not sure if I will keep the remote variometer tuning. It =
needs some extra wires to the loading coil and I am not sure how long =
the small DC motor will function properly with all the rain and frost =
coming up.

      Here it holds since more than 2 years for LF now..

      73, Stefan


--=20
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK
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<META content=3D"text/html; charset=3DISO-8859-1" =
http-equiv=3DContent-Type>
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</HEAD>
<BODY bgColor=3D#ffffff text=3D#000000>
<DIV><FONT size=3D2 face=3DArial>Rik, Stefan, I follow your points but =
there would=20
seem to be something strange in Rik's antenna or his appreciation of =
what/how=20
its working. </FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Contrary to an earlier assertion, the =
antenna=20
current flowing through Rrad generates the radiated power, so lower =
current, if=20
Rrad doesnt change, MUST mean lower tranmitted power.&nbsp;It matters =
not that=20
the SWR is unity. A unity SWR indication at the transmitter says that =
the=20
impedance at the end of the coax is 50ohms, but it does not necessarily =
indicate=20
the the the antenna is resonant i.e the inherent capacitance of a short =
antenna=20
totally compensated by the loading inductance. If we assume that =
Rrad+Rloss does=20
not change across the band the matching transformer should transform the =
value=20
of Rrad+Rloss to 50 ohms across all the band. The coax will now be =
matched and=20
will present 50ohms at the shack end. If this does not happen I would be =

inclined to suspect currents induced in the coax braid. SWR =
indicators&nbsp;can=20
easily be confused by induced braid currents......could this be the =
cause of=20
Riks strange effects? This might be a function of having a "better" =
ground in=20
the shack than at the base of the antenna.</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Alan</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>G3NYK</FONT></DIV>
<DIV>&nbsp;</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=3DStefan.Schaefer@iup.uni-heidelberg.de=20
  href=3D"mailto:Stefan.Schaefer@iup.uni-heidelberg.de">Stefan =
Sch=E4fer</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> Friday, November 08, 2013 =
6:53=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: LF: remote antenna =

  tuning</DIV>
  <DIV><BR></DIV>Oh yes, or, a phase meter (M0BMU) and a battery =
operated=20
  variometer motor. Without an additional cable to the shack. Then the =
SWR meter=20
  in the shack confirms that everything is fine.<BR><BR>73, =
Stefan<BR><BR>Am=20
  08.11.2013 19:40, schrieb pat:=20
  <BLOCKQUOTE cite=3Dmid:527D300A.7000909@aol.com type=3D"cite">
    <DIV class=3Dmoz-cite-prefix>Hi All,<BR><BR>A suggestion: battery =
operated=20
    tuning device at antenna end and "wireless" link back to shack. =
Wireless can=20
    operate at a non-interfering frequncy=20
    (HF/VHF/UHF/Optical).<BR><BR>73<BR><BR><BR><BR><BR><BR><BR>On =
08/11/13=20
    16:09, Stefan Sch=E4fer wrote:<BR></DIV>
    <BLOCKQUOTE cite=3Dmid:527D0CCB.6090208@iup.uni-heidelberg.de =
type=3D"cite">Hi=20
      Rik,<BR><BR>Am 08.11.2013 16:06, schrieb Rik Strobbe:=20
      <BLOCKQUOTE=20
      =
cite=3Dmid:7E7DFBB4D102A04DB5ADC88D66628A4A0FC98037@ICTS-S-MBX1.luna.kule=
uven.be=20
      type=3D"cite">
        <DIV=20
        style=3D"FONT-FAMILY: Tahoma; DIRECTION: ltr; COLOR: rgb(0,0,0); =
FONT-SIZE: 10pt">
        <P>Hi&nbsp;Stefan,</P>
        <P>&nbsp;</P>
        <P>remote&nbsp;tuning of=20
        =
the&nbsp;loading&nbsp;should&nbsp;be&nbsp;done&nbsp;by&nbsp;optimizing&nb=
sp;SWR=20
        (at the TX),&nbsp;not&nbsp;for maximum&nbsp;RF current.</P>
        <P>If&nbsp;one&nbsp;keeps&nbsp;that in&nbsp;mind&nbsp;there =
is&nbsp;no=20
        problem.</P></DIV></BLOCKQUOTE>...which is in agreement with =
what i=20
      said.<BR>But once you have matched your antenna to 50 Ohm on =
resonance and=20
      you can only vary the reactive part of the antennas impedance =
(after doing=20
      QSY), then you will get the maximum antenna current at best SWR =
(assuming=20
      that Rrad+Rloss is constant which is not to far from =
reality).<BR><BR>
      <BLOCKQUOTE=20
      =
cite=3Dmid:7E7DFBB4D102A04DB5ADC88D66628A4A0FC98037@ICTS-S-MBX1.luna.kule=
uven.be=20
      type=3D"cite">
        <DIV=20
        style=3D"FONT-FAMILY: Tahoma; DIRECTION: ltr; COLOR: rgb(0,0,0); =
FONT-SIZE: 10pt">
        <P>I&nbsp;am&nbsp;not&nbsp;sure&nbsp;if I&nbsp;will keep=20
        the&nbsp;remote&nbsp;variometer =
tuning.&nbsp;It&nbsp;needs&nbsp;some=20
        extra&nbsp;wires to the&nbsp;loading&nbsp;coil and=20
        I&nbsp;am&nbsp;not&nbsp;sure&nbsp;how long =
the&nbsp;small&nbsp;DC=20
        motor&nbsp;will&nbsp;function&nbsp;properly&nbsp;with all =
the&nbsp;rain=20
        and&nbsp;frost coming up.</P></DIV></BLOCKQUOTE>Here it holds =
since more=20
      than 2 years for LF now..<BR><BR>73, Stefan<BR><BR>
      <BLOCKQUOTE=20
      =
cite=3Dmid:7E7DFBB4D102A04DB5ADC88D66628A4A0FC98037@ICTS-S-MBX1.luna.kule=
uven.be=20
      type=3D"cite">
        <DIV=20
        style=3D"FONT-FAMILY: Tahoma; DIRECTION: ltr; COLOR: rgb(0,0,0); =
FONT-SIZE: 10pt"></DIV></BLOCKQUOTE></BLOCKQUOTE><BR><BR><PRE =
class=3Dmoz-signature cols=3D"72">--=20
73 de pat g4gvw
es gd dx
qth nr Felixstowe
East Coast UK</PRE></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>

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