Message-ID: <000701c29094$87da85c0$ea00a8c0@f3a3a2>
From: "Laurie Mayhead" <laurie@g3aqc.freeserve.co.uk>
To: rsgb_lf_group@blacksheep.org
References: <000701c29080$5c4c19a0$402d7ad5@main>
Date: Wed, 20 Nov 2002 12:57:03 -0000
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Subject: LF: Re: re Spiral
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----- Original Message -----
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: "LF-Group" <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, November 20, 2002 10:32 AM
Subject: LF: re Spiral


> Hi Steve, that sounds quite a beastie. we only got to 700 or so
uH.....1.4mH
> top load sounds very interesting. I think the problem is that you will not
> get any help from "analysis" as most of the theoretical treatments dont
seem
> to be able to deal with inductive top-load and the effect of increased
> top-capacitance on ground loss. My guess is that you will not see much
more
> increase in Rrad now, but I cant judge what effect further development
will
> have on the ground loss.
>
> You are certainly going the right way to judge from our experiments.  The
> problem on ground loss is that the foot-print (as Laurie would call it) is
> defined by the sillouette of the spiral so doesnt really increase with the
> amount of wire used.  Our ground loss only started to decrease when we put
> top-load wires out from the apex above the spiral but then "covering new
> ground". I suspect you will have to get the best you can with ground wires
> ("radials") probably earthed at the ends, like woulld be needed for a true
> vertical.  You obviously will not need much inductance at the bottom to
tune
> up to resonance. Are you able to make any measurements on the structure
yet
> ??
>
> This is a very interesting project.
>
> Cheers de Alan G3NYK
> alan.melia@btinternet.com
>
 Hi Alan and Steve,
If I can put my bit in here I think that the spiral top load will be a nice
low loss inductor but as Alan says, in itself it will not "see" much ground.
Rrad depends on the height of the vert. section so it will not increase, The
great advantage of the spiral will be to increase the potential of whatever
top wire you can manage to get up,making it more effective,but as I have
said boringly so many times,  the more the better,its the  "foot print" that
matters and the worse the ground the bigger the foot print needs to be"Wire
in the air has 100 times more worth than wire in the air " There I've said
it again sorry.
73 Laurie .
>
>
>
>
>