Message-ID: <199908252258.IAA16769@godzilla.zeta.org.au>
From: "Steve Olney" <ollaneg@zeta.org.au>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Re: SV: Multiple Tuned Vertical
Date: Thu, 26 Aug 1999 08:51:53 +1000
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Christer wrote:

> If six such antennas are parallelled, the total loss resistance becomes
1/6 while the radiation resistance remains unchanged. The total impedance
is now 0,45 ohm due to reduced losses.
> The antenna input power is fed by 1/6 of the total current (feed
impedance is raised by a factor 36).
> By varying the current distribution between the verticals (by changing
the tuning coils) a suitable feed impedance can be achieved. 20 ohm in the
SAQ case.
> 
> It seems like the ratio of  Rrad/Rloss is increased. Corresponding
thougths can be found in the ARRL Antenna book edition 17 p4-21.
> 
mmm... interesting that this description disagrees with the ARRL handbook
description.. I quote.

"If ground losses are also considered, the effective loss resistance (RL)
would also be transformed by the same amount."

It goes on to say that it is the distribution of the ground currents which
will USUALLY improve the ratio Ra/Rl.   So the real improvement seems to
come from the reduction in losses through better earth current distribution
(see Bob Vernall's post).   This is unlikely to be anywhere near an
improvement of N*N. I am especially pessimistic as for many of us who are
LF-challenged, the major part of the losses are trees and buildings which
won't be reduced.

As I said before, this is all theory and even practical examples from the
commercial world can be unattainable in the less than ideal amateur
installations, so the final words on this will have to be practical
experimentation from different amateur installations.

73s Steve Olney (VK2ZTO/AXSO - QF56IK : Lat -33 34 07, Long +150 44 40)
=============================================
LowFer URL:
http://www.zeta.org.au/~ollaneg/lowfer.htm
AXSO Experimental Station URL:
http://www.zeta.org.au/~ollaneg/axsoextx.htm
LF Receiving - FRG-100
LF Transmitting - 177.5kHz 8W to 7.6m top-loaded vertical
Modes - AM, SSB, PSK31, SSTV, Hellschreiber and QRSS
=============================================