If the SWR on an antenna feed line is 5:1, and a matching network at the transmitter end of the feed line is adjusted to present a 1:1 SWR to the transmitter, what is the resulting SWR on the feed line?
Why SWR on a feed line is set by the mismatch between the line's characteristic impedance and the load at its far end, which is the antenna. A matching network (antenna tuner) at the transmitter end only transforms the impedance the transmitter sees; it does nothing to the antenna's feed point impedance, so the reflected wave on the line is unchanged and the line still runs at 5:1. The tuner just re-reflects that returning power back toward the antenna, and the line continues to suffer the extra loss that comes with 5:1 SWR.
Watch out Reading 1:1 is tempting because that is what the SWR meter at the transmitter shows once the tuner is adjusted, but that reading applies only to the short section between the tuner and the radio, not to the whole feed line.
A tuner fools the radio, not the feed line. SWR is set at the antenna end and stays there.