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[TowerTalk] bandwidth vs efficiency

To: <>, <>,"Jim Lux" <>
Subject: [TowerTalk] bandwidth vs efficiency
From: "Tom Rauch" <>
Reply-to: Tom Rauch <>
Date: Tue, 8 Jun 2004 13:33:18 -0400
List-post: <>
> >Let's submerge our screwdriver mobile antennas in a
> >container.  An additional advantage would be that no bugs
would nest
> >in there!
> >
> >73,
> >
> >   George T. Daughters, K6GT
> reducing the loss in the coil will make the bandwidth
narrower.  You run
> into this when you contemplate making high efficiency
compact loops.  Sure,

The mobile system is dominated by ground loss. In my large
F250 supercab truck the grounding loss was about 10 ohms on
80 meters. Increasing loading coil Q by a factor of three
doesn't have near the effect on bandwidth that changing the
VALUE of reactance does. If I add a large hat so as to
reduce inductance by three-fold, bandwidth is roughly three
times larger. This can occur even while efficiency increases
substantially, because the ground loss swamps out resistance
changes in the overall system.

My narrowest 160 meter mobile antenna is also the least
efficient by a considerable margin.

Loops, being a closed system, are different. Unless of
course they are near a very lossy media.

73 Tom


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