Dear Mr. Reid: Very many thank's for your great information regarding the
Johnson Matchbox. Now I can probably use it on the WARC
bands as well! On another matter, for those who notice what a very large size
the Johnson Kilowatt matchbox is should note that It
was originally designed to handle 1000 watts of 100 percent plate modulated AM.
I am terrible at math, but I believe this is
equivalent to 4000 watts of peak envelope power ssb!!! From looking at the
quality and size of the capacitors and coils and tend to
agree it could handle that! - Sherrill W.
>>> "Jim Reid" <kh7m@hsa-kauai.net> 03/29/00 07:57PM >>>
Sherill wrote, in part:
> I don't mean to keep beating a dead horse, but I really
> get a good laugh when some of you microprocessor
> types tell me what narrow bandwidth my old Johnson
> Matchbox has!
Hi,
My guess is they mean "instantaneous bandwidth"; or
how many kHz you can QSY the rig and still have a
good match to the feedline/antenna system before
having to tweak the Matchbox a bit, just a guess
of course.
I have modified my Johnson kW Matchbox such that
I now have a variable C in series with the primary
link; also have each of the primary links tapped.
The unit operates very smoothly now compared to
the un-modified original. Very first step is to
resonate the primary via tap switching and the
primary link tuning cap. Get excellent matches
to all sorts of who-knows what I've put out the
window now, hi!
Am about to order one of those true 600 ohm open
ladder line set ups from: http://www.w7fg.com/ant.htm .
Just have to figure out where to string a 200+ foot
long, center fed flat top; might have to settle for
the 130+ foot 80 meter and up version.
All the data about modifying the Matchbox is available
at the W4RNL web site:
1. All about the Johnson Matchbox, with several photos,
http://www.cebik.com/link.html
2. Modifying them ideas and details,
http://www.cebik.com/link0.html
note, this comes in five parts, very interesting, IF
and only if, you really want to know how the Matchbox
works, and what can be done to improve same.
Enjoy,
73, Jim, KH7M
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