[Elecraft] High SWR

[DK5EW]

Hi all,
I used my K3 only with transverter on 2m. Now the 6m season is starting 
and I connected it to my 6m beam.
On 50 MHz as I pushed TX I got "high SWR" message. K3 SWR meter showing 
3:1 bad SWR.
I measured with my mini vna analyser the antenna and it is perfect. SWR 
real is 1:1
So it must be a failure in the K3 ?
Yes I have a tuner build in BUT thought SWR must be perfect without tuning ?
Or is it necessary to use tuner if build in ? When I tune SWR is 1:1.1
Please further info if possible.

-- 
best regards
Erwin/DK5EW