[Elecraft] KS3/P3 SWR Display Readings

[Don Wilhelm]

Ferris,

I am assuming that you are referring to the SWR displayed from the P3 
Transmit Monitor which is placed in your feedline to the antenna.  If 
other than that, please correct me.

The SWR displayed on the Transmit monitor is the SWR on the transmission 
line to the antenna - in other words, it is the SWR at the *output* of 
the tuner in the K3S.
The wattmeter in the K3S indicates the SWR at the *input* of the KAT3.  
It tunes to 'keep the K3S finals happy'.  That will not change the SWR 
on the feedline to the antenna.

If you were to place the TX monitor sensor between the K3S PA and the 
KAT3 (impossible to connect there), then the TX monitor and the K3S 
should agree.
In other words, the term "Antenna Tuner" is not an entirely correct 
term.  It does not change the SWR on your antenna and feedline, but 
instead transforms the SWR at the output into a low SWR at its input.
An ATU is a system of lumped components that compensates for the SWR on 
the antenna and feedline and transforms it to a low SWR at its input to 
match the 50 ohms resistive match wanted for maximum efficiency from the 
transceiver PA transistors.

In other words, the K3S is showing you the SWR at the *input* of the 
KAT3, but the SWR at the *output* of the KAT3 will not be changed. If 
you want to change that, you will have to work on your antenna and 
feedline system.

73,
Don W3FPR

On 12/18/2015 7:35 PM, Ferris Jennings wrote:
> Hell-o Everyone -
>
>   
>
> Finished building my K3S and P3 (with TX Mon), and I'm starting to play with
> the configuration/menus.
>
> I have the KAT3 ATU installed, and it works great. But I do have a question
> regarding the SWR displays.
>
>   
>
> I'm running a simple diploe, and the KAT3 tunes it down to 1.0-1 in a second
> flat. However, the SWR meter on the PS display always reads way higher,
> something like 2.9 - 1. I've swapped antennas and lead (another dipole), and
> I get the same results.
>
>   
>
> Question is: why the discrepancy in SWR from the K3S display to the P3
> display? Am I missing a configuration setting?
>
>   
>