[Elecraft] K3 SWR Accuracy - reprise

[Don Wilhelm]

Wes and all,

It is not unreasonable to expect some frequency dependency in the 
detection diodes as well.
The tuner will function properly in any case - it tunes for the lowest 
SWR no matter what the exact value of that SWR may be. 

Now, if the SWR = 1.0 point was not correct, that would say there may be 
a problem with the tuning.
Those wanting a more accurate SWR indication of the antenna side may 
want to consider the new Elecraft W2 as well.

73,
Don W3FPR


Wes Stewart wrote:
> I suggest a reading of Larry's original paper on the design of the LP-100 to understand the heroic efforts needed to make these measurements with any accuracy.
>
> see: http://www.telepostinc.com/Files/phipps-1.pdf
>
> It should come as no surprise that the K3's built-in directional coupler lacks the directivity of the ones in Larry's LP-100, and directivity is extremely important in this application.
>
> For an example left to the reader to work out, measure a load with 20 dB return loss using a coupler with 20 dB directivity and see what the uncertainty is.
>
> Wes Stewart  N7WS
>
>   
>