[Elecraft] K3 SWR Accuracy - reprise

[Eric Swartz - WA6HHQ, Elecraft]

How long is the coax between the LP100 sensor and the K3? This can have 
a significant impedance transformation impact as you go to higher 
frequencies, leading to a different indicated SWR at each end.

73, Eric


Stewart wrote:
> Hi,
> Now traffic on the new K3 Macro functions has somewhat died down, 
> I would like to raise again the issue of the K3's SWR measurement 
> accuracy.
>
> I did some tests using dummy loads and a LP-100 meter as follows.
>
> The dummy load is a precision 100W one which I measured with a VNA
> and has a VSWR of <1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR
> I used another dummy load (not quite as good) in parallel.
>
> The K3 output was from ANT1 using the internal ATU. The ATU was
> automatically tuned to 1:1 on all bands.
> The results I got for 2:1 VSWR are as follows:-
>
>                LP-100           K3
> 160         1.99                1.8
> 80           1.99                1.8
> 60           1.99                1.8
> 40           1.95                1.8
> 30           1.97                1.6
> 20           1.97                1.4
> 17           1.97                1.3
> 15           1.96                1.2
> 12           1.96                1.5
> 10           1.96                1.4  
>
> As can be seen my K3 SWR indication consistently under reads.
> However, it really gets bad on 20,17 & 15.
>
>  From previous replies I understand that this under reading would  
> be compensated for in the firmware, sometime in the future . 
>
> Is this still on the list of problems to be addressed ?
>
> 73
> Stewart G3RXQ
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