Electrical conductivity of the Great Lakes

A cri tical exa mination has bcen made of the electrical co ndu ct ivity valu es ass igned, for radio propagation purposes, to t he waters of the Great Lakes. Discrepa ncies between co nductivi ty values measured in t he laboratory and t hose deduced from fi eld s t rength measurements are shown to have been t he resul t of both expenmental error and the use of faul ty standard t heoretical fi eld strength cmves. The latter source of errol' is the result of e rror in thc standard curves t hemselves and lll t he usc of a d lelectn c cons tant of 15 for overwater propagation. Condu ctivi ty valu es derived frOl.n laboratory m easuremen ts of water sa mples are sign ifi ca ntly d ifferent from those published In co nd uc!,lvlty maps. Lal:ge seasonal var iat ions in conductivity, approac hi ng a factor of two 11l some cases, a rc a slgnlfi cant complicating fac tor.