The L/C ratio, in turn, determines their Q and so their selectivity, because the rest of the circuit - the aerial or amplifier feeding the tuned circuit for example - will contain present resistance.
For a series resonant circuit, the higher the inductance and the lower the capacitance, the narrower the filter bandwidth (meaning the reactance of the inductance, L, and the capacitance, C, at resonant frequency will be relatively high compared with the series source/load resistances).
For a parallel resonant circuit the opposite applies; small inductances reduce the damping of external circuitry (see electronic oscillator).
There are practical limits to the increase in selectivity with changing L/C ratio: Therefore other methods may be used to increase selectivity, such as Q multiplier circuits and regenerative receivers.
Superheterodyne receivers allow use one or more fixed intermediate frequency tuned circuits for selectivity.