Another good reference is at ARRL Site URL:
http://www.arrl.org/tis/info/pdf/9401070.pdf
Titled "Do You Need An Antenna Tuner"

73 From The Signal In The Noise
Caveat Lector Ya All
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If you could answer yet another question. How does a autotransformer
work exactly? I can see how you can tap up and down the coil to hit a
certain point where you can a 50 ohm match. But when I look at the
schematic all I see is a coil in parallel with a variable cap. How
does the autotransformer in essence become a transformer? Or rather
how does it become the above schematic?

On the second question you might be better off to read the antenna
matching
chapter in any Radio Amateurs Handbook. :}