[Elecraft] K3 SWR Readout Accuracy Question

[Ron D'Eau Claire]

Even if your cable is good, a change in length will have an effect on the
SWR between two meters (internal to the K3 and your external meter). The
effect will be greater with increasing frequency and increasing SWR. 

Also, the accuracy of typical SWR bridges is best only at 1:1, and decreases
as the SWR rises. Their function is to show a matched condition (1:1) with
reasonable accuracy. 

If you want to see how closely the measurements agree, connect your bridge
to the K3 with a minimum length connector  - directly mount it onto the K3
with an adapter and avoid all cables is best. 

Ron AC7AC

-----Original Message-----

On my newly assembled kit K3/10 without the internal ATU, I've noticed
that the SWR readouts are "higher" than those on my K2 which agrees with
my analog inline meter.  Into a 50 ohm dummy load all three readings are
1.0:1, but on an actual antenna the readings differ.

For example, where my K2 and  the analog meter read 1.4:1, the K3 says
1.9:1.  this variance increases as the SWR increases and decreases as
the actual SWR decreases, hence the agreement among all three measures
on 1:1 when operating into a dummy load.

All readings taken at 5 watts, same antenna, same  SG-237 autocoupler,
same cable routings, and the internal ATU in the K2 bypassed.  The only
variable is the actual 48"coax jumper going from the K3 to the patch
panel.

I just finished the K3 yesterday so I am just a K3 beginner. However I
could find nothing in the manual about SWR calibration.

Any pointers would be appreciated.  Other than this, everything appears
to be working great and the K3 DSP is fabulous.

Stan WB2LQF
K3 #5244



73, Ed - KL7UW, WD2XSH/45