[Elecraft] Re: KX1 antenna experiments

[wayne burdick]

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