adic ▁E ▁ion os pher ic ▁du ct ing ▁can ▁make ▁the ▁ 4 6   M Hz ▁and ▁below ▁frequencies ▁un work able ▁in ▁summer . ▁ ▁As ▁links ▁ ▁For ▁dec ades , ▁cross - band ▁repe aters ▁have ▁been ▁used ▁as ▁fixed ▁links . ▁The ▁links ▁can ▁be ▁used ▁for ▁remote ▁control ▁of ▁base ▁stations ▁at ▁distant ▁sites ▁or ▁to ▁send ▁audio ▁from ▁a ▁divers ity ▁( v oting ) ▁receiver ▁site ▁back ▁to ▁the ▁divers ity ▁combining ▁system ▁( v oting ▁compar ator ). ▁Some ▁legacy ▁links ▁occur ▁in ▁the ▁US ▁ 1 5 0 – 1 7 0   M Hz ▁band . ▁US ▁Federal ▁Communic ations ▁Commission ▁rule ▁changes ▁did ▁not ▁allow ▁ 1 5 0   M Hz ▁links ▁after ▁the ▁ 1 9 7 0 s . ▁Ne wer ▁links ▁are ▁more ▁often ▁seen ▁on ▁ 7 2 – 7 6   M Hz ▁( M id - band ), ▁ 4 5 0 – 4 7 0   M Hz ▁inter st it ial ▁channels , ▁or ▁ 9 0 0   M Hz ▁links . ▁These ▁links , ▁known ▁as ▁fixed ▁stations ▁in ▁US ▁lic ens ing , ▁typically ▁connect ▁an ▁equipment ▁site ▁with ▁a ▁dispatch ing ▁office . ▁ ▁Ve h icular ▁repe aters ▁ ▁Modern ▁amateur ▁rad ios ▁sometimes ▁include ▁cross - band ▁repeat ▁cap ability ▁native ▁to ▁the ▁radio ▁trans ce iver . ▁ ▁In ▁commercial ▁systems , ▁cross - band ▁repe aters ▁are ▁sometimes ▁used ▁in ▁veh icular ▁repe