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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