[Elecraft] KX-1 power output varies

[Barry N1EU]

I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
times I notice anywhere from about 1.9 to 3 watts power output.  In all
cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
power output varies so much.  Is this due to varying losses in the tuner as
the match varies at different locations?

Thanks & 73,
Barry N1EU