It's important to know and keep in mind that the SWR meter doesn't actually
measure the SWR on the feedline. So its reading doesn't prove or disprove
anything about how the SWR on a feedline changes with length.

Hi, Roy

yes, that is the reason why I was talking of "apparent" or "measured" SWR,
whilst the real SWR does not vary with line length.

1. The feedline Z0 isn't exactly 50 ohms. The Z0 of coax easily varies +/- 5
ohms from nominal, and sometimes closer to +/- 10 -- it's seldom exactly 50.
If you connect a perfect 50 ohm load to your transmitter via a 45 ohm line,
the impedance seen by the transmitter will change with line length.
Consequently, the SWR meter reading will also change. The actual SWR on the
line will not, except as dictated by loss, described next.

2. The feedline has loss. The SWR will improve as the line becomes longer due
to line loss. If the line is long enough to be very lossy, the transmitter
will see nearly the line's Z0 regardless of what load is connected to the
other end. The actual SWR on the line will be greatest at the load, decreasing
as you get farther away.

3. There is current on the outside of the coax shield (common mode current).
When this happens, the feedline becomes part of the antenna. Consequently,
changing the feedline length actually changes the effective antenna length,
which in turn changes the feedpoint impedance.

I would say that in case no. 1 the meter measures an apparent SWR, whilst in
case no. 2 it measures the real SWR existing at the measurement point. I am not
sure what it measures in case no. 3

Regards.

Tony I0JX