One thing I forgot.
The SWR goes down when you add a little inductive reactance to the antenna (make it too long, or operate higher than resonance). For best performance it is always best to operate at resonance and match the resistive portion. You'll also find out that using an UNUN will give you a little more 2:1 bandwidth than you have with out it. Incidentally, inductive and capacitive impedance matching is not as broad banded as an UNUN. This is why I prefer them over other matching techniques.