▁only ▁to ▁the ▁radio ▁signal ▁it ▁is ▁tun ed ▁to ▁( such ▁as ▁a ▁radio ▁station ) ▁and ▁reject ▁other ▁signals ▁nearby ▁in ▁frequency , ▁such ▁as ▁another ▁broadcast ▁on ▁an ▁adjacent ▁channel . ▁ ▁Select ivity ▁is ▁usually ▁measured ▁as ▁a ▁ratio ▁in ▁de ci b els ▁( d B ), ▁comparing ▁the ▁signal ▁strength ▁received ▁against ▁that ▁of ▁a ▁similar ▁signal ▁on ▁another ▁frequency . ▁If ▁the ▁signal ▁is ▁at ▁the ▁adjacent ▁channel ▁of ▁the ▁selected ▁signal , ▁this ▁measurement ▁is ▁also ▁known ▁as ▁adjacent - channel ▁re jection ▁ratio ▁( AC R R ). ▁ ▁Select ivity ▁also ▁provides ▁some ▁imm unity ▁to ▁blank eting ▁inter ference . ▁ ▁L C ▁circ uits ▁are ▁often ▁used ▁as ▁filters ; ▁the ▁Q ▁(" Qual ity " ▁factor ) ▁determ ines ▁the ▁band width ▁of ▁each ▁L C ▁tun ed ▁circuit ▁in ▁the ▁radio . ▁The ▁L / C ▁ratio , ▁in ▁turn , ▁determ ines ▁their ▁Q ▁and ▁so ▁their ▁select ivity , ▁because ▁the ▁rest ▁of ▁the ▁circuit ▁- ▁the ▁aer ial ▁or ▁ampl ifier ▁feed ing ▁the ▁tun ed ▁circuit ▁for ▁example ▁- ▁will ▁contain ▁present ▁resistance . ▁For ▁a ▁series ▁reson ant ▁circuit , ▁the ▁higher ▁the ▁induct ance ▁and ▁the ▁lower ▁the ▁capac it ance , ▁the ▁nar ro wer ▁the ▁filter ▁band width ▁( mean ing ▁the ▁react ance ▁of ▁the ▁induct ance , ▁L , ▁and ▁the ▁capac it ance , ▁C , ▁at ▁reson ant ▁frequency ▁will ▁be ▁relatively ▁high ▁compared ▁with ▁the ▁series