While tuning a radio station on a radio set why we usually change value of c?

In an LC circuit, f=1/2 pi(1/LC)¯¹.So in order to increase or decrease the frequency we move the moving capacitor plate from the stationary one. (capacitance is inversely varied as distance between the two plates. Frequency inversely varies as square root of capacitance. Thus frequency directly varies as square root of d.)