Guys, my money is on the connector on the feedline. It must have a
short developed since the last time you used it. Or the short might be
at the antenna feed point.
The feed line length is just not a factor even when there is RF on
the shield, and there is some.
The MFJ Antenna Analyser will find the problem. I love mine.
73 Karl K5DI
Dan Presley wrote:
-------------------------------------------------------
You should not have had any trouble with a center fed dipole, Dan.
The issue
with the KX1 ATU, as with any ATU, is impedance extremes. Because of the
limited number of inductors and capacitors that could be fitted into the
tiny space available in the KX1, it has a more limited tuning range
than any
of the other Elecraft tuners.
The end of a dipole presents a very high impedance, possibly in the
thousands of ohms. At the other extreme, a very short antenna will
present a
very low impedance, often less than an ohm. Actually, end-fed short
antennas
often tune up more easily because they are working against ground and
typically Hams have lousy RF grounds <G>. Even with several "radials"
the
ground impedance will likely be in the tens or, more likely, the
hundreds of
ohms. That's in series with the antenna so what the tuner is matching
is a
total impedance of perhaps a hundred ohms or more. The fraction of an
ohm
that the antenna represents is just part of the total. It's also why
such
antennas have a very, very low efficiency: often less than a few
percent.
In your case, I'd suspect you had an unlucky length of feed line.
Unless the
SWR is truly 1:1 on that feeder, something that is almost never
achieved in
practice, the feed line acts like a random impedance transformer. I
suspect
you got unlucky and the combination of the effect of surrounding
objects,
antenna length, feeder impedance and feeder length all added up to an
impedance the KX1 ATU couldn't handle. Adding a few feet of feed line
will
usually fix that.
Another possibility is a short or open, as you suggested.
Ron AC7AC
Thanks,Ron and all of those who replied for the good advice. I'm
betting you're right on the money as far as feedline length. I'll put
the antenna back up and check it with my dipper to see how it reads,
and also with the rig in 'cal' (tuner bypass) mode. That'll tell me
also if there's a short somewhere too. I tend to forget about the
feedline length as I often just use an endfed wire from the KX1, or at
home I use ladder line. I know this can still happen with ladder line,
but perhaps less of an issue than coax.Besides, the ol' Johnson
matchbox is pretty forgiving:)
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