Why the change in SWR? Because something physical changed with the antenna, as in it's relation to the things around it, it's environment. (It can make a difference.)
Better to use a tuner at the transmitter end or use the existing "tuner" at the antenna's input? If you use a tuner at the transmitter's end of the feed line then the feed line becomes 'part' of the antenna. The mismatch is still there, but it's been transformed to something close to what the transmitter want's to see. Since the impedance mismatch is still there, there will still be the losses associated with that mismatch, you'll basically 'loose' some power. By using the existing 'tuner', the rings on that antenna, you've eliminated the feed line as a source of loss because of a mismatch in impedance. So, which would you think would be the better idea? Sure, it'll be more trouble to do, but the results will probably be more noticeable.
And just to keep things in perspective, there are losses associated with any impedance transformation. They don't necessarily amount to a lot, but they are always there. The smaller those losses the more 'acceptable' they are.
- 'Doc
(What you need is a trained antenna monkey. They'll do the climbing and adjusting, you just have to feed them...)
