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Re: [TowerTalk] Grading a ground radial system

To: <Jamesnf@aol.com>, <Dinsterdog@aol.com>,<towertalk@contesting.com>
Subject: Re: [TowerTalk] Grading a ground radial system
From: "K3GM" <k3gm_qrp@verizon.net>
Date: Sat, 14 May 2005 12:29:52 -0400
List-post: <mailto:towertalk@contesting.com>
Doesn't the feedpoint impedance vary according to the frequency?  Paul, N0AH
didn't tell us at what frequency he was taking reading.  I experienced the
same "problem" when erecting a 40 meter home brew wire vertical over a
radial field of 100 33' wires.  My feedpoint impedance was extremely low.  I
sort of fixed it by adding a few turns of coiled wire for about 2uH of
inductance at the base of the radiator.  Problem is the bandwidth is
narrowed drastically.  I'm going to attempt to remedy this by using a remote
antenna tuner like the Icom AH-4 at the base of the antenna.  Even as it is
now, the antenna works beyond anything I even imagined.  No doubt, the big
radial field is the reason.

7 3, Tom Hybiske K3GM

----- Original Message ----- 
From: <Jamesnf@aol.com>
To: <Dinsterdog@aol.com>; <towertalk@contesting.com>
Sent: Saturday, May 14, 2005 11:29 AM
Subject: Re: [TowerTalk] Grading a ground radial system


> Hi Paul:
>
> Your measured impedence drops with the radials detached because there is
less
> loss in the system.  With an extensive radial system, your impedence
should
> drop to the vicinity of 32 ohms with a quarter wave, lossless radiator.
>
> I would be more interested in how the radial system is impacting field
> strength than in how it is impacting impedence.  You can always design and
install a
> matching network at the feedpoint to achieve an impedence match between
your
> feedline and the antenna.  What you want to do with you radial system is
> increase field strength.  When you've done the best you can with your
radial
> system, given wire and space available, measure the resulting impedence
and match to
> it if necessary.  Don't build the radial system to acheive some desired
> impedence.
>
> 73,  Jim W9TM
>
>

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