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Re: LF: G8IMR - stronger? ...and G3XBM on 136kHz WSPR this evening

To: <[email protected]>
Subject: Re: LF: G8IMR - stronger? ...and G3XBM on 136kHz WSPR this evening
From: "Alan Melia" <[email protected]>
Date: Thu, 6 Jan 2011 12:40:01 -0000
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Hi Andy yes that makes sense.......Finbars measurements showed that the
situation recovered once (almost immediately) the rain stopped though the
ground was still wet......that shows a slightly different effect??  Finbars
tower is reasonably clear of "environment."

Alan

----- Original Message ----- 
From: "Andy Talbot" <[email protected]>
To: <[email protected]>
Sent: Thursday, January 06, 2011 8:57 AM
Subject: Re: LF: G8IMR - stronger? ...and G3XBM on 136kHz WSPR this evening


> We put it down to an increase in lossy paralle resistance.
> In dry conditions, the reactive (out of phase) near field current
terminates
> on ground radials without passing through too much (relatively speaking)
> lossy ground material.
>
> When everything is covered in water, the reactive field is conducted away
> into lossy ground material before entering the radials.  Being resistive,
> the current moves into phase with the E-field and ,starts to introduce
added
> I^2R loss.  Most significantly here, walls and roof tiles the top-hat
passes
> close to become more conductive, extracting noticably in-phase currents
from
> the E field.
>
> The result is a *decreased* resistance in *parallel *with the antenna
> capacitance, and when you plug decreased parallel R into the equation for
> parallel-to-serial transform, voila, an *increased series* term.
>
> The tuning shifts marginally, but it was far worse when the effect was
first
> discovered on 73kHz.
> Was that really well over a decade ago - time flies!
>
> Andy
> www.g4jnt.com
>
>
>
> On 5 January 2011 23:28, Alan Melia <[email protected]> wrote:
>
> > Yes that is what my aerial measurements said as well in
rain....increased
> > loss resistance.....not sure though whether it is a ground effect or the
> > film of water on the wire.
> >
> > Alan G3NYK
> >
> > ----- Original Message -----
> > From: "Andy Talbot" <[email protected]>
> > To: <[email protected]>
> > Sent: Wednesday, January 05, 2011 3:33 PM
> > Subject: Re: LF: G8IMR - stronger? ...and G3XBM on 136kHz WSPR this
evening
> >
> >
> > > No - no changes at all.
> > >
> > > The only difference is that it is raining now.which - by the way these
> > > things work - has *increased* the antenna resistance and reduced power
> > > output by a dB or two.
> > >
> > > Andy
> > > 'JNT / 'IMR
> > >
> > >
> > >
> > > On 5 January 2011 14:53, Roger Lapthorn <[email protected]>
wrote:
> > >
> > > > Hi Andy,
> > > >
> > > > Your 136kHz WSPR beacon is coming in very well today at
around -6/-7dB
> > S/N
> > > > at 188km. Have you made some further ERP improvements?  PA0A is also
a
> > very
> > > > good signal too.
> > > >
> > > > I hope to be TXing on 136kHz WSPR this evening ....but with a rather
> > weaker
> > > > signal than these two. Any reports (at all) would be very much
> > appreciated.
> > > >
> > > > 73s
> > > > Roger G3XBM
> > > > --
> > > > g3xbm-qrp.blogspot.com/
> > > > www.g3xbm.co.uk
> > > > www.youtube.com/user/g3xbm
> > > > <http://vlf_grabber/>G3XBM   GQRP 1678    ISWL G11088
> > > >
> > >
> >
> >
> >
>



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