The various automatic antenna tuner/matcher manufacturers list a
tuning range in Ohms - e.g., 6 - 1000 Ohms. The question I have is to
whether that value is the magnitude of the impedance (which correlates
to SWR) or the real part of the impedance (since the tuner should be
able to cancel out the reactive part of the impedance). W0BF

Bruce W. Ellis wrote:
The various automatic antenna tuner/matcher manufacturers list a
tuning range in Ohms - e.g., 6 - 1000 Ohms. The question I have is to
whether that value is the magnitude of the impedance (which correlates
to SWR) or the real part of the impedance (since the tuner should be
able to cancel out the reactive part of the impedance). W0BF

neither, really. What it probably means is that, theoretically it can
transform a resistive load of 6-1000 ohms to 50 ohms.

You actually have to look at the available L and C and decide if it can
tune a particular reactive load at a particular frequency. The step size
for L and C will also determine how good the final match is.

You can write a little program (or spend some serious time with a smith
chart) to iterate through the various possibilities, essentially working
backwards from a 50 ohm load impedance to see the possible input Zs it
can match.

"Bruce W. Ellis" ha scritto nel messaggio
...
The various automatic antenna tuner/matcher manufacturers list a
tuning range in Ohms - e.g., 6 - 1000 Ohms. The question I have is to
whether that value is the magnitude of the impedance (which correlates
to SWR) or the real part of the impedance (since the tuner should be
able to cancel out the reactive part of the impedance). W0BF

Firstly, it should be noted that the magnitude of the impedance (Z) does NOT
correlate to SWR. As a matter of fact, the formula giving SWR as a function of
resistance (R) and reactance is such that R-X pairs corresponding to the same Z
magnitude may well yield different SWR figures and, conversely,.R-X pairs
yielding the same SWR figure generally correspond to different Z magnitudes.
This can be readily visualized on the Smith chart.

For instance the pair R=30 ohm, X=40 ohm yields an SWR of 3, that is the same
SWR produced by the pair R=150 ohm, X=0 ohm, despite the two Z magnitudes are
different (50 ohm in the first case, 150 ohm in the second one).

That said, an excerpt of the MFJ-993B autotuner manual reads: "... it is rated
at 300 watts to match 6 to 1600 ohms antennas (SWR up to 32:1)"

In my opinion, as a load of 1600 ohm would actually yield an SWR of just 32, the
MFJ sentence makes reference to a pure R of 1600 ohm (that is with X=0). As a
matter of fact, a Z magnitude of 1600 ohm, if not purely resistive, could
correspond to quite a wide range of SWR figures, and not necessarily to 32..

The cited sentence excerpt then tells nothing about the tuner ability to
neutralize the reactance of reactive loads.

On the other hand one must consider that, for the sake of limiting the internal
switching arrangement complexity, automatic tuners usually adopt an L-type
network in which the reactive element connected at the antenna (either in series
or in parallel, depending on whether a step-up or a step-down transformation of
the R is required) is not switcheable, i.e. it is either an inductor or as a
capacitor. This means that a tuner may inherently be more tolerant of capacitve
loads with respect to inductive loads, or viceversa, depending on the way it is
designed.

73

Tony I0JX

Bruce W. Ellis wrote in
:

The various automatic antenna tuner/matcher manufacturers list a
tuning range in Ohms - e.g., 6 - 1000 Ohms. The question I have is to
whether that value is the magnitude of the impedance (which correlates
to SWR) or the real part of the impedance (since the tuner should be
able to cancel out the reactive part of the impedance). W0BF

Bruce,

Where an impedance range is loosely specified as you quote (dimensioned in
ohms without identification of the R and X parts), and in the absence of
applicable frequency constraints and loss figures, I think you can safely
disregard the information as unprovable advertising hype.

It is intended to look technical, something to impress the new wave of hams
who don't have the understanding, and not enough to reliably determine the
suitability of the ATU to a specific application.

Owen

Owen Duffy wrote:
Where an impedance range is loosely specified as you quote (dimensioned in
ohms without identification of the R and X parts), and in the absence of
applicable frequency constraints and loss figures, I think you can safely
disregard the information as unprovable advertising hype.

It is intended to look technical, something to impress the new wave of hams
who don't have the understanding, and not enough to reliably determine the
suitability of the ATU to a specific application.

The matching range of a typical tuner can be estimated
by playing with the simulated tuner at:
http://fermi.la.asu.edu/w9cf/tuner/tuner.html
Select the frequency and load needing to be matched,
click auto, and see if the tuner can match it.

I wonder if Kevin would be interested in making the
tuner's CLC values user specifiable?

I have modeled tuners with Microsmith (an old DOS
program) and varied the C1, L, C2 values while watching
the trace on the Smith Chart. Given all possible
combination of CLC values, the result would be the
matching envelope of the tuner at a specified frequency.

What would be nice is a program that would automatically
plot the tuner's matching envelope on a Smith Chart given
the input parameters.
--
73, Cecil http://www.w5dxp.com

On Oct 24, 7:33*am, Cecil Moore wrote:
Owen Duffy wrote:
Where an impedance range is loosely specified as you quote (dimensioned in
ohms without identification of the R and X parts), and in the absence of
applicable frequency constraints and loss figures, I think you can safely
disregard the information as unprovable advertising hype.

It is intended to look technical, something to impress the new wave of hams
who don't have the understanding, and not enough to reliably determine the
suitability of the ATU to a specific application.

The matching range of a typical tuner can be estimated
by playing with the simulated tuner at:http://fermi.la.asu.edu/w9cf/tuner/tuner.html
Select the frequency and load needing to be matched,
click auto, and see if the tuner can match it.

I wonder if Kevin would be interested in making the
tuner's CLC values user specifiable?

I have modeled tuners with Microsmith (an old DOS
program) and varied the C1, L, C2 values while watching
the trace on the Smith Chart. Given all possible
combination of CLC values, the result would be the
matching envelope of the tuner at a specified frequency.

What would be nice is a program that would automatically
plot the tuner's matching envelope on a Smith Chart given
the input parameters.
--
73, Cecil *http://www.w5dxp.com

There used to be a ham near me that use an auto tuner to feed a
doublet. I dont think the antenna was cut for any particular frequency
just the most wie he could get strung from corner to corner of his
yard. He found he could get it to tune up on all the HF bands but only
by changing the length of his feedline between the tuner and antenna.
I was thinking it may be nice to have a tuner that could control an
external relay to switch in/out custom networks for adapting it to
site specific operating conditons.

Jimmie

JIMMIE wrote:
He found he could get it to tune up on all the HF bands but only
by changing the length of his feedline between the tuner and antenna.
I was thinking it may be nice to have a tuner that could control an
external relay to switch in/out custom networks for adapting it to
site specific operating conditons.

Why even have a tuner if you are going to switch the length
of the feedline?

http://www.w5dxp.com/notuner.htm

In my Arizona implementation of this antenna, I used
relays driven by a 80C51 microcontroller to achieve
an autotuner function.
--
73, Cecil http://www.w5dxp.com

On Oct 24, 3:05*pm, Cecil Moore wrote:
JIMMIE wrote:
He found he could get it to tune up on all the HF bands but only
by changing the length of his feedline between the tuner and antenna.
I was thinking it may be nice to have a tuner that could control an
external relay to switch in/out custom networks for adapting it to
site specific operating conditons.

Why even have a tuner if you are going to switch the length
of the feedline?

Because it would require only one external switch, be useful on random
lengths of antenna, probably a few more I could think of if I didnt
have to get to work.

Jimmie