On Jul 7, 2004, at 10:16 PM, Doug Forman wrote:
I guess it's just interesting to me that the internal tuner does such
a GREAT job matching the 135' slinky dipole on both 20 and 40 meters,
but falls apart on 30 meters. It's also interesting to me that the
internal tuner NICELY matches the MA5V on 40 meters (it's only a
10-20m vertical with a SWR of 7.6 on the antenna analyzer at 7055khz).
Hi Doug,
The KXAT1 was designed with medium-length random wires in mind. It has
a fairly limited Z-matching range, and may have a rough time with very
low-Z or high-Z loads. In your case, the L and C values provided just
happened to hit a sweet spot on the Smith chart with your 40-meter
tuneup on the vertical. And a sour spot on 30 with the slinky dipole
;) The L and C steps are fairly coarse, so with loads like this, it
will be hit-or-miss.
If you want to make sure the KXAT1 is working as intended, try the
"sorta-vertical" we recommended in the KXAT1 manual: toss about 20 to
25' of wire into a tree, and lay out a 16' radial on the ground. The
L/C values were tuned for this easy-to-erect field antenna.
The ATU also does a great job with not-quite-resonant antennas.
Example: the Maldol AH-14 20-meter whip. This whip is tuned for the
high end of the band, but the ATU finds a match close to 1.0:1, making
the transmitter happier. Without it, the SWR is over 3:1.
73,
Wayne
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