Jay wrote:
All tuners will eat up some percentage of your RF output power.
The ones with toroid or smaller inductors may eat up more power.
Jay, John, etc.:
The physical size of the inductors would only be a factor if they were
also inefficient (dissipating a lot of heat). In all of our tuners,
including the T1, we use high-Q toroidal inductors with core and wire
sizes appropriate for the intended RF current. In addition, we use
high-Q capacitors (NP0/C0G ceramic or in some cases silver mica).
In lab tests of the T1, I used loads from 3 to 1000 ohms, calculating
the power into and out of the L-network. The T1's efficiency was on a
par with other tuners of this type, including those with much larger
toroids. For typical matches, losses range from 0.1 to 1 dB. A tuner
using very large air-wound inductors and air-variable capacitors might
cut these values in half, and would have an advantage at very high or
low impedances. But such a unit would also not be very portable, so
it's a tradeoff.
A much bigger factor in most antenna installations is ground loss,
which usually dwarfs any L-network losses. This is especially true of
portable antennas. If your goal is to radiate the best possible signal,
you can reduce ground losses by using *lots* of radials, or consider a
dipole or inverted V with its feedpoint as high off the ground as
possible.
When I'm in casual operating mode I simply toss a wire in a tree, lay
out one radial, use no feedline at all, and accept the inevitable
ground loss. If I'm "serious," I string a wire between two trees such
that the center is 20 to 30 feet high, feed it with 300-ohm low-loss
twinlead, and use a low-loss balun between the feedline and the tuner
(the Elecraft BL1 is quite small and works well in this application).
In this cases I use a wire that's at least 1/2-wavelength long on the
lowest band of operation.
The T1 finds a low-SWR match on most or all HF bands with either
"casual" or "serious" antennas :)
73,
Wayne
N6KR
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