Roy Lewallen wrote:
"Under what circumstances is the line SWR affected by the source
impedance which feeds the line?"

None that I kbow of, but I can imagine a control mechanism that adjusts
the impedance presented to the antenna to reduce SWR.

To avoid responding to: "But, how about the "Matchmaker System", which I
never herd of, I added the word "usually". As far as I know, there is
usually nothing that can be done at the transmitter end of the line to
affect SWR. Match between the load and line controls SWR.

Best regards, Richard Harrison, KB5WZI