A summary is prese nted of the ways in whi ch the concept of system loss a nd the close ly related concepts of transmission loss, basic transm iss io n loss, propagation loss, and pat h ~ntellna gain ma y be used for precise, yet s imple, description s of so me of t he characteris tics of rad io wave propaga tion which are important in t he des ign of rad io syste ms. D efini t ions of various terms associated with the co ncept of syste m loss a re give n which in trodu ce a greater fl exibility into its use without any loss in precis ion. I t is shown t hat t he usc of thC'se added terms and concepts ma kes feasible the extens ion of the usc of t his method of descript ion t o a ny portion of the ra dio spectrum. A more general formula for the syste m loss is give n which may be used for anten nas with an arbitrarily sma ll separa t ion. Usin g t his formll l~ it is shown that t he syste m loss betwee n s m~ll elect ric or magnet ic dipoles separated by a distance d « A can be made arbitrarily small even though t he individua l a nte nn as have la rge circuit losses. Formulas are developed for the perce ntage of t im e t hat a des ired signal is free of in terference, a nd these a re used to demonstrate methods for t he e ffi cient use of the spectrum. In particula r, contrary to general belief, it is show n t hat efficie ncy is promoted by t he use of high power a nd hi gh ant~nnas and, in the case of a broad cast ser vice, s uffici ent ly srnall separations so t hat t here is appreciable mu t ual in terfe re nce. A n a na lys is is mad e o f t he varia nce of t he path a ntenna gain in ion osp heri c scatter propagation. Met hod s a re g ive n for t he calculatio n of the tra ns mi ssion loss for t he gro und wave an d tropospheric scatter modes of propagation thro ugh a turb ul ent model at mosphere w it h a n expo nen t ia l grad ient. Examples of such calculation s are g iven which cover a wide ra nge of frequ cncies a nd antc nn a heights. Finall y, cxamples are given of t hc expected ra nge o f various t ropospheric poin t-to-point scatter syste ms s uch as a n FM m ul t icha nn e l teletype systcm, a telev ision relay or a n FM br oadcast relay.