Re: KX3 ATU

Posted by vk4tux on Sep 19, 2012; 6:52am
URL: http://elecraft.85.s1.nabble.com/KX3-ATU-tp7495809p7562966.html

Matt, Of course I don't question Don's technical stature, however "tuning
the antenna" is a poor choice of explanation, and can give a false
impression to those weak on the subject. Adding 'system' would have been a
good move as you indicate. We tune where we measure.

-----Original Message-----
From: Matt Maguire [mailto:[hidden email]]
Sent: Wednesday, 19 September 2012 3:35 PM
To: vk4tux
Cc: [hidden email]
Subject: Re: [Elecraft] KX3 ATU


On 19/09/2012, at 2:48 PM, vk4tux <[hidden email]> wrote:

> Don, When you say "The ATU will tune the antenna to an acceptable
> SWR", you are contradicting yourself, because as you rightly said the
> tuner does not change the antenna feedpoint swr.

It is clear from the context that Don meant the ATU will tune (ie. match)
the antenna *system* to the radio, where the antenna system consists of the
ATU, antenna and connecting feedline considered as a single unit. This of
course does not mean that the VSWR is 1:1 everywhere within that system.

The theory predicts that the measures VSWR will be constant along a
*lossless* feedline. As you point out, practical feedlines do have losses.
This will include I^2.R copper losses, but there can be losses from other
sources as well, such as dielectric losses. Often such losses will be
modelled as some sort of equivalent series resistance.

73, Matt VK2ACL=

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