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References: <9afca2641001210904h7d2b276dv503b55075ce9313@mail.gmail.com>
Date: Thu, 21 Jan 2010 19:21:21 +0000
Message-ID: <fc7eccec1001211121r756dbd91le43bf04c04427c5d@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
DomainKey-Status: good (testing) 
Subject: Re: LF: M0BMU - any chance of some new ERP estimates please?
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The type of ground locally probably enters into the propagation equation
without influence on the ERP figure, and may be enhancing my signals a dB or
so.   For example, I am on quite good conductive heavy clay, and there is a
lot of it in the area.    I've sunk something like 15 x 1 to 2m long copper
tubes and rods into it all round the small gargen, and cros slinked them in
a completely random way  in lieu of being able to put out any worthwhile
radials.  This may have (quite inadvertently) been a *good thing.*

Back in the 73kHz days, several stations were surprised just how good a
signal was getting out from my antenna,  quite significantly smaller than
those of just about every other operator on that band.   Down on 73k,
measuring efficiency in the same way as the ratio of Rrad to Rload, I
estimated -48 to -50dB gain giving 1mW ERP from 100 W.   This seemed to
stack-up with received signal stregths and the more predictable propagation
loss estimates down on those frequencies.

Mind you, the local vegetation and trees by the antenna have grown since
then, but I strongly suspect the resulting near-field lossey capacitance is
absorbed into the loss resistance, so more-or-less correctly appears in the
efficiency calculation without having to be added in as a frig-factor.
Anyway, won't this component have less contribution at 7 times the
frequency?
The most surprising finding back then was how much the loss resistance
increased when it rained - when one would have expected a decrease in wet
conditions.   Once the lossy near-field termination effect was realised, it
all made sense.

Andy
www.g4jnt.com


This email has been scanned for damaging side-effects by the health and
safety police, is guaranteed to contain no substances hazardous to health,
but may contribute to dissolving the nether and polar regions


2010/1/21 Roger Lapthorn <rogerlapthorn@gmail.com>

> Dear Jim,
>
> Following the discussion on the LF reflector in the last 24 hours, I wonder
> if we could use your experience and expertise to estimate the most recent
> ERP levels for G4JNT, G3ZJO and G3XBM please. Based on Rik's figures we've
> some doubt whether Andy G4JNT is being a little optimistic or whether Eddie
> and I are being pessimistic or whether the truth is somewhere in between.
>
> Would much appreciate this. Thanks
>
> 73s
> Roger G3XBM
>
> --
>
> http://g3xbm-qrp.blogspot.com/
> http://www.g3xbm.co.uk
> http://www.youtube.com/user/G3XBM
> G3XBM    GQRP 1678      ISWL G11088
>

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<div>The type of ground locally=A0probably enters into the propagation equ=
ation without influence on the ERP figure, and may be enhancing my signals=
 a dB or so.=A0=A0 For example,=A0I am on quite good conductive heavy clay=
, and there is a lot of it in the area.=A0=A0=A0 I&#39;ve sunk something=
 like 15 x 1 to 2m long copper tubes and rods into it all round the small=
=A0gargen, and cros slinked them in a completely random way=A0=A0in lieu=
 of being able to put out=A0any worthwhile radials.=A0 This may have (quit=
e inadvertently) been a <strong>good thing.</strong></div>

<div>=A0</div>
<div>Back in the 73kHz days, several stations were surprised just how good=
 a signal was getting out from=A0my=A0antenna, =A0quite significantly smal=
ler than those of just about every other operator on that band.=A0=A0 Down=
 on 73k, measuring efficiency=A0in the same way as the ratio of Rrad to Rl=
oad, I estimated -48 to -50dB gain giving 1mW ERP from 100 W.=A0=A0 This=
 seemed to stack-up with received signal stregths and the more predictable=
 propagation loss estimates down on those frequencies.</div>

<div>=A0</div>
<div>Mind you, the local vegetation and trees by the antenna=A0have grown=
 since then, but I strongly suspect the resulting near-field lossey capaci=
tance is absorbed into the loss resistance, so=A0more-or-less correctly ap=
pears in the efficiency calculation without having to be added in as a fri=
g-factor.=A0 Anyway, won&#39;t this component have less contribution at=A0=
7 times the frequency?</div>

<div>The most surprising finding back then was how much the loss resistanc=
e increased when it rained - when one would have expected a decrease in we=
t conditions.=A0=A0 Once the lossy near-field termination effect was reali=
sed, it all=A0made sense.</div>

<div><br clear=3D"all">Andy<br><a href=3D"http://www.g4jnt.com/">www.g4jnt=
.com</a></div>
<div><br><br>This email has been scanned for damaging side-effects by the=
 health and safety police, is guaranteed to contain no substances hazardou=
s to health, but may contribute to dissolving the nether and polar regions=
<br>
<br><br></div>
<div class=3D"gmail_quote">2010/1/21 Roger Lapthorn <span dir=3D"ltr">&lt;=
<a href=3D"mailto:rogerlapthorn@gmail.com">rogerlapthorn@gmail.com</a>&gt;=
</span><br>
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">Dear Jim,<br><br>Following the=
 discussion on the LF reflector in the last 24 hours, I wonder if we could=
 use your experience and expertise to estimate the most recent ERP levels=
 for G4JNT, G3ZJO and G3XBM please. Based on Rik&#39;s figures we&#39;ve=
 some doubt whether Andy G4JNT is being a little optimistic or whether Edd=
ie and I are being pessimistic or whether the truth is somewhere in betwee=
n.<br>
<br>Would much appreciate this. Thanks<br><br>73s<br>Roger G3XBM<br clear=
=3D"all"><font color=3D"#888888"><br>-- <br><br><a href=3D"http://g3xbm-qr=
p.blogspot.com/" target=3D"_blank">http://g3xbm-qrp.blogspot.com/</a><br><=
a href=3D"http://www.g3xbm.co.uk/" target=3D"_blank">http://www.g3xbm.co.u=
k</a><br>
<a href=3D"http://www.youtube.com/user/G3XBM" target=3D"_blank">http://www=
.youtube.com/user/G3XBM</a><br>G3XBM =A0 =A0GQRP 1678 =A0 =A0 =A0ISWL G110=
88<br></font></blockquote></div><br>

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