[Lowfer] Ultimate LOWFER Transmitter? Ooops !!!!!

[Steve Olney]

G'day Stewart,

Oooops !!! Scale all efficiencies down by 100 :-)    Comes from hitting the
% key AND multiplying by 100 :-(      It *was* 3:30am when I did these
calculations.

Steve

----- Original Message -----
From: Steve Olney <ollaneg@zeta.org.au>
To: <lowfer@mailman.qth.net>
Sent: Saturday, March 16, 2002 5:05 AM
Subject: Re: [Lowfer] Ultimate LOWFER Transmitter?


> G'day Stewart and All,
>
> Neither the radiation resistance nor the loss resistance is a real
> resistance in the sense that you can't use simple circuit analysis to give
a
> picture of what is happening.    Radiation resistance is just a resistance
> in which the power radiated appears to be dissipated.    The loss
resistance
> is just the resistance in which the non-radiated power appears to be
> dissipated.   Some of this loss is "lumped" in the coil loss and some is
> distributed in ground and environmental losses.
>
> Taking your assumption that the "base" lowfer antenna has an 0.02 ohm
> radiation resistance, a 20 ohm loss resistance (ground + coil loss), and
is
> tuned to be a 20 ohm resistive load at the operating frequency.    Assume
a
> 50% split between ground/environmental and coil loss (10 ohm each).   This
a
> generous split to help your case as much as possible - mine system here is
> about 90% ground/enviromental and 10% coil.  The efficiency of your
example
> is 0.02/20 = 10%.
>
> Now split the single radiator in two but separated by, say,  just 1m with
> each radiator having a series coil and joined at the base.    The
radiation
> resistance stays the same at 0.02 ohm,  the ground/environmental loss
> resistance stays the same at 10 ohms, but the coil resistances are in
> parallel and are reduced to an effective 5 ohms.    So now the efficiency
is
> 0.02/(10 + 5) = 13.333%.   This is a gain of a little over 1dB - not 3dB.
> Note this same gain could have been done more simply by just making the
> original signal coil with less loss.     Increasing the spacing does not
> alter this scenario as long as you are not running out of space with the
> original ground system and the spacing becomes a significant fraction of a
> wavelenth.   Putting a 100 radiators in parallel closely spaced would only
> reduce the losses in the coil by 100 and so the limiting gain for this
would
> be an efficiency of about 20% (0.02/10).   This is a gain of 3dB maximum.
> Note this is with the same amount of wire/netting/sheet in the ground
system
> for both scenarios.    Adding more wire/netting/sheeting for multiple
> radiators while leaving the single radiator with its original
> wire/netting/sheeting is not playing fair.
>
> Much simpler to roll out the chicken wire as far as possible under your
> single radiator system to reduce the ground losses,  fire up the chainsaw
to
> reduce the environmental losses (a.k.a. trees and bushes) and use as high
a
> Q coil as possible on a single mast.    Hey - isn't that what you guys had
> done already ?
>
> 73s Steve Olney VK2ZTO
>
> "Man made mathematics and models, but God made reality"
>
>
> _______________________________________________
> Lowfer mailing list
> Lowfer@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/lowfer