[Elecraft] [KX3] SWR display wrong?

[Matt Zilmer]

The difference between an SWR of 1.3 and 1.1 is minimal.  There is
probably some calibration error between the KX3 and MiniVNA.  There is
also stray C & L in each, so that may contribute to the difference.  I
don't know if a forward/reverse power calibration is approved for the
KX3, but it's not shown in the owner's manual.

Very low power levels might also be a problem.  At low power levels,
the ADC that reads the directional coupler output is working at a low
range, with reduced resolution (small number of ADC output bits
compared to a higher power level).  Some call this "resolution error".

I've heard it said that SWR less than 2 is pretty fair and within
operating limits of most transmitters.  The KX3 is no exception.

Just did a comparison at 5W between KX3 and LP-100A (factory
calibrated).  The KX3 shows 1.4 SWR and the LP-100A shows 1.7, both
done on the same dummy load, with the ATU in bypass.  

I wouldn't worry about the difference.  In actual power terms, the
reflected power is extremely low in either case.

73,
matt W6NIA

On Sun, 29 Dec 2013 22:26:24 +0100, you wrote:

>My KX3 #4475 shows SWR 1.3 when I press tune and send into a dummy load. 
>I checked cable and dummy load with a MiniVNA pro and my K3, both show perfect SWR of 
>1.0 and 50 ohm. The KX3 has no tuner built in. 
>
>Any hints where to look?
>
>73! de Werner OE9FWV