In article ,
Wayne wrote:

On the 43 foot vertical it could be that the 4:1 unun provides a lower
amount of SWR induced additional feedline loss on high Z feedpoints. Of
course, the unun might increase the SWR induced additional feedline loss for
smaller Z.

From the charts, that kinda does appear to be the case.

Add into consideration the fact that losses go up with the square of
the current.

Another issue is the other aspect of SWR - voltage. If you're trying
to run "legal limit" or close to it, high SWR on the feedline coax
could exceed the voltage rating of the coax dielectric, and you'd get
arcing in the coax (or arcing at the connector between your feedline
and shack tuner).

Installing a hefty 4:1 unun right at the antenna would reduce the
worse-case voltage on the feedline, and inside the shack tuner
considerably. Depending on feedline length, that might be even more
of a consideration than the increase in peak feedline current and the
associated I^2*R losses.