▁usually ▁requires ▁very ▁little ▁or ▁no ▁circuit ▁modification , ▁depending ▁on ▁the ▁choice ▁of ▁radio . ▁ ▁For ▁instance , ▁the ▁Motor ola ▁model ▁GT X ▁( mobile ▁and ▁hand h eld ▁versions ) ▁do ▁not ▁require ▁any ▁hardware ▁modifications ▁at ▁all . ▁ ▁Using ▁these ▁commercial ▁rad ios ▁however , ▁has ▁one ▁hand ic ap : ▁flex ibility . ▁ ▁Un like ▁most ▁other ▁ham ▁radio ▁bands , ▁in ▁which ▁one ▁can ▁t une ▁to ▁any ▁frequency ▁within ▁an ▁amateur ▁band , ▁modification ▁of ▁" Channel ized " ▁commercial ▁rad ios ▁maintain s ▁them ▁in ▁a ▁channel ized ▁state . ▁ ▁Therefore , ▁once ▁program med , ▁the ▁frequencies ▁they ▁operate ▁on ▁cannot ▁be ▁changed ▁at ▁will ▁without ▁re - programming . ▁ ▁However , ▁since ▁almost ▁all ▁FM ▁radio ▁equipment ▁used ▁on ▁the ▁ 3 3   cm ▁band ▁amateur ▁band ▁was ▁previously ▁designed ▁for ▁and ▁internally ▁program med ▁for ▁frequencies ▁outside ▁the ▁ 3 3   cm ▁band ▁edges , ▁re programming ▁is ▁always ▁necessary ▁to ▁get ▁them ▁working ▁properly ▁between ▁ 9 0 2 - 9 2 8   M Hz ▁after ▁any ▁physical ▁modifications ▁have ▁been ▁made . ▁ ▁This ▁includes ▁the ▁GT X . ▁ ▁Link ing ▁Many ▁am ateurs ▁have ▁found ▁the ▁ 3 3 ▁cent imeter ▁band ▁to ▁be ▁ideal ▁for ▁linking ▁repe aters ▁together . ▁Some ▁of ▁the ▁biggest ▁linked ▁repe ater ▁systems ▁in ▁the ▁United ▁States ▁use ▁the ▁ 3 3 ▁cent imeter ▁band ▁as ▁their ▁link ▁back bone . ▁ ▁Pro pag