A coil and an air-spaced capacitor are arranged to form a resonant circuit. The resonant frequency will remain the same if we:

The resonant frequency of a tuned circuit is determined exclusively by the values of its inductance (L) and capacitance (C). If neither of these values changes, the resonant frequency remains exactly the same. Altering the physical characteristics of the components, such as inserting a dielectric like Mylar between capacitor plates, increasing plate area, or adding turns to the coil, will change either the capacitance or the inductance. This directly shifts the resonant frequency. Adding a resistor, however, does not alter the inductance or the capacitance. While it will increase energy loss and widen the circuit's bandwidth (lowering the Q-factor), the actual center frequency of resonance is completely unaffected.