[Elecraft] [K3] KAT3 and 160 with 40m long doublet

[Don Wilhelm]

  The length of the radiator is only half the story.  Unless the 
feedline is matched to the impedance at the antenna feedpoint, there 
will be SWR on the transmission line.
When there is SWR on the transmission line, the type of line and its 
length become important when comparing whether any given antenna will 
work the same as any other antenna of the same length.
So if you do not state the type and length of your feedline, it is like 
comparing apples to oranges.
If you do not understand this phenomenon, take a look at the Antenna, 
Transmission Line, Tuner article on y website www.w3fpr.com.

*If* it just so happens that the KAT3 cannot tune a particular antenna, 
then the impedance in the shack may be very low or very high (out of the 
range of the tuner).  Adding or subtracting a 1/8 wavelength of feedline 
will often bring it into range, and that is normally the easiest 
solution if the only thing you are considering is the ability of the 
tuner to produce a match.

73,
Don w3FPR

On 1/2/2011 5:39 PM, Tony Estep wrote:
> On Sun, Jan 2, 2011 at 3:18 PM, Dr. Detlef Petrausch<dl7ndf at t-online.de>wrote:
>
>> I use a 40.8 m long windom and it's no problem to tune to a swr abt. 1.2
>> with the KAT3 on the 160m band....
>
> Yep, similar results here. I have used 7 different ATUs and the KAT3 is the
> best by far. The antenna can be way shorter than 1/2 wave and still tune up
> fine.