Message-ID: <37C777F5.3441@xtra.co.nz>
Date: Sat, 28 Aug 1999 17:47:34 +1200
From: "vernall" <vernall@xtra.co.nz>
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Multiple Tuned Vertical : simple calculations
References: <3.0.1.16.19990827143645.268f4bda@mail.cc.kuleuven.ac.be>
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Rik Strobbe wrote:
> But what to do with the 'loss resistance' (RL) in the real world ?
> Assume a simple model where both tuned sections share the same
> ground-system. In that case RL would be in series with R and this would
> mean that a double tuned vertical would not only quadruple the radiation
> resistance but also the loss resistance, resulting in an unchanged ratio
> between radiation resistance and loss resistance.

Which is basically what I meant in my previous comments about
"transformer action" from the division of current between multiple tuned
vertical feeds.  It is similar to a folded dipole transformation. 
Overall, multiple tuned verticals are still a similar antenna structure
from the point of view of "looking back at it from some distance away". 
Multiple tuned vertical parts are an "impedance transformation trick"
but do very little, if anything, for the net radiation resistance of the
whole antenna.  Where some advantages are likely is in the multiple
grounds.

Bob ZL2CA