Suppose your antenna has some strange impedance of, say, Zant=20+i60 ohm (red dot). Then, you need to do something so that the impedance seen from the transmitter becomes, at least close enough to, Z0=50+i0 ohm (orange dot).
This can be done in several different ways, but one thing worth remembering is that the impedance itself, Zant=20+i60 ohm in this case, is not very essential, although this is the value you observe with an antenna analyzer when it is attached to the feeding point of your antenna.
More essential is the constant gamma circle (red) on which the various impedances you will observe through a different length of a coax cable will all appear.
Note: The gamma=(Zant-Z0)/(Zant+Z0), abs(gamma)=0.7276,
and VSWR=(1+abs(gamma)) / (1-abs(gamma))=6.342.
By varying the cable length, the reactance, the imaginary part of the impedance, becomes either inductive (upper half of the plane) or capacitive (the lower half of the plane), or the impedance be purely resistive (on the X=0 axis).
Now, one more step to go from the red dot to the orange dot.
Starting form the red dot, you can select any point on the red circle by changing the cable length, and since you only wish to use purely reactive devices for your impedance matching network to avoid any power loss, you are moving on the green circle on which the R is 50 ohm everywhere, to reach your destination, the orange dot.
These two circles, red and green, will determine the mid-point (blue dot), to where you will move from the red dot, and from where you will move to the orange dot.
One example is shown here. With the frequency of 18.1MHz, the cable lenght of 496.5mm will bring you from the red dot (Zant=20+i60 ohm) to the green dot (Zmid=50+i106 ohm), and the series capacitance of 83pF (Zc=-i106 ohm) at the near end of the cable will bring you from the green dot to the cyan dot (Z0=50 ohm). (The coloring differs, but you will understand.)
Then, you can use a cable of any length to connect your transmitter and the 83pF capacitance + 496.5mm cable + your antenna.