[TowerTalk] ++ High SWR and Modern Transceivers

[Jim Reid]

Alex wrote,  in part:

> Tom. You are promulgating wrong ideas and concepts which 
> will repeated by the neophyte.

Nonsense!  Tom is absolutely correct!

Go to the University of Chicago web site where a tuner
simulator is set up.  Read the instructions,  use your
antenna system analyzer to determine the actual 
R and X of the impedance at the end of the feed
line to be connected to the tuner output terminals.
Put the values into the simulator and see the result.
To do this experiment for your own tuner,  you need
to know component values of the C's and L or the unit.
Or,  lacking that info,  use the default values for experimenting.

Simulator is here:

http://fermi.la.asu.edu/w9cf/tuner/tuner.html

You will find that in just about every case,  either the input
or output C value will be selected for maximum!  If the
Z at the tuner output terminal is much below 50 ohms,
especially on 160,  80,  and even 40,  you may have to
have some extra capacity available to switch in parallel
with the output C if your output variable is only 350 pf,
or so;  then will probably need another 200 or more pf.
If the Z at the "back" of the tuner of the antenna feed is
high,  then note that the input C will be set to its' maximum
value.  Why?  That is the lowest loss,  highest efficiency
set up,  just as Tom has said.

I have used this simulator,  once I knew the component values
within  my tuner,  to establish the optimum setting areas for
my operating antenna systems and band/frequencies,  neat!

One tuner  which used to be/is made,  the XMatch is designed
with only one variable C.  The other is a "bank" of parallel
fixed capacitors.  These are interchanged between the input
and output positions  thus,  something like 500 pf,  fixed is
placed at the output position for low Z loads,  and the opposite
for high Z antenna feed system inputs.  The designer/supplier
has this switching function patented.  Why is it designed with
fixed capacitors for one set?  Because that is one
good way to insure the user doesn't mess up,  hi.

73,  Jim  KH7M





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