One reason you got different results with the different core sizes is that the cross sectional area is different. FT50 .133 cm squared FT82 .246 FT114 .375 The working flux density goes down as the cross sectional area increases. -- FAQ on WWW: http://www.contesting.com/topband.html Submissions: topband@contesting.com Administrative requests: topband-REQUEST@contesting.com Problems: owner-topband@contesting.com