Frequency dependence of D-region scattering at VHF

R esult s are gi ve n of a on e-year progra m of obser vation of fl'cq u e n c ~; dcp nd ence o f syste m loss for D-region scatt ering at VHF. Con t inuous simul ta neous obser va t ions were m ad e at fiv e fr eq ue ncies from 30 to 108 M c/s, using na rrow beam an t enn as scaled in di mellsion s a nd h eight a ccordin g to wavele ngth ; t he p at h was from . Long Bran ch, Ill. , t o Bo ulder, Colo. , a di sta nce of 1,300 km . Ho urly valu es o f system loss closely fo ll owed t he relatio nship P'/Paoc jn . The value of n varied wi th t ime o f da y a nd sea so n, wit h 90 p ercen t of a ll observatio ns ly in g i n t he ra nge 7 to 97~ fo r scaled a nt e nna syst ems. Diurna l a nd seasonal va riatio n of n a re a t t ri buted to changing relative roles of turb ulen ce an d m eteoric r eflectio ns. E ff ects o f norm a l io nospheric a bsor ption a re not a pparent. A special analysis is mad e of freq ue ncy d epe nd ence durin g wea k sig na l co ndi t ions. H csults a re a lso given of st udi es o f t he fr eq uency d r pendence of fad ing charact eri st ics, Lhc d reet of beam width , a nd SI J) behavior.