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Tuner Thread encore

Subject: Tuner Thread encore
From: John Brosnahan <broz@csn.net> (John Brosnahan)
I probably should say something in defense of the Johnson
KW Matchbox.  They were really designed for balanced feedline
and I have no doubt that they can handle 5KW into a higher
impedance load (they have capacitors with wide plate spacing)
and they probably have a wider range of reactance matching
when used with high impedance balanced feedlines.

Most of the "modern" antenna tuners are single ended Tees
and are designed for a coaxial (unbalanced) feedline and when 
used with balanced feedlines utilize a balun transformer.  But the
transformer is really not properly terminated in most
cases and may become a significant source of loss (translate
heat, smoke, and fire).

Bottom line--modern tuners for coax, Johnson KW 
Matchbox for balanced lines and I am curious about
what is so unique about the X-Match.

If you really just want to "flatten" the SWR on your
coax fed antenna there is a good article in the Antenna
Compendium Vol 3 by W6PY showing that a FIXED
inductor combined with two variable caps can match
anything within the 5-1 SWR circle (for a given band).

To see the Johnson KW Matchbox's further development
you can read "Beyond the Z-Match " by W6JJZ in
Communications Quarterly Winter 95.

73  John  W0UN

(Does this constitute a bar-be-cue?  I added a little (technical) 
meat to the (Matchbox) flame!)

John Brosnahan  
La Salle Research Corp      24115 WCR 40     La Salle, CO 80645  USA
voice 970-284-6602            fax 970-284-0979           email broz@csn.net


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