"Newby" on Fri, 16 Mar 2007 08:17:34 CST wrote:

"Bill Horne, W1AC" wrote in message

While a "Garden Variety" tuner may be OK for a coax-fed dipole if it's
near to resonance, other feedlines and an antenna further from resonance
will need a more robust design.

Of course, some tuners have switching for multiple antennas, and some
don't, so let us know if you're using a single cloudburner, or multiple
skyhooks.

[snipped]

Don't have the antenna(s) yet.

I am looking for a "more robust" design that will tune almost anything, an
automatic tuner rather than a manual one, and don't need switching between
multiple antennas.

The majority of automatic antenna tuners now made have some
form of frequency sensing to set their internal setting
memories. The majority of types will handle 100 W PEP RF
which fits the average manufactured transceiver of today.
Depending on the type/model, they can cover just the HF
spectrum or the HF plus 6m.

The single most important technical factor (after power
handling and frequency range) is the RANGE of impedance
magnitude that can be matched. That will vary depending on
type/model but a typical magnitude range is 6 to 1200 Ohms.
That is roughly the ability to handle SWR maximums of 8:1
to ~20:1. Baluns can be used to extend either end of the
range as needed. Most autotuners will indicate something if
they can't get a match so that lets you know.

Note I said Magnitude of the impedance to be matched. That
includes both the resistive part and the reactive part of
the impedance to be matched. The reactive part can be
capacitive or inductive but the autotuner will set itself
to match either...then it will set itself to match the
resistive part as close as the designers chose to 50 Ohms.

The end result is an autotuner that can handle the very low
impedances of mobile whip antennas to certain conditions of
frequency with long-wire antennas where the impedance
magnitude can be very high. As far as matching range goes,
the "robustness" is very good on all models within their
RF power range specifications. No sweat. :-)

73, Len AF6AY