There is a lot more going on in the antenna tuner but basically if the antenna is too short the tuner "adds" wire by increasing inductance. Conversely if the antenna is too long capacitance is added.
It's not as simple as just adding one component, there is some really clever impedance matching that goes on as well.
Last edited by XL189; 20th Aug 2017 at 21:35.
Reason: bad grammer