Avner, You'll have to supply more information. It's unclear what you're really after. The Dielectric Constant of a material is "constant" for the most part at the frequency of concern. Depending upon alot of other factors, like the frequency you're working at versus how the dielectric was tested, you could get different values. Dielectric material has a mathematical "complex" side to it. Enough! It sounds like you're working some sort of calculation for microstrip, buried microstrip, or stripline constructions and getting different values for dielectricity. That by itself is NOT good. More info? doug ______________________________ Reply Separator _________________________________ Subject: Controlled Impedance - Dielectric Constant Author: [log in to unmask] at internet-mail Date: 5/21/96 8:15 AM Subject: Controlled Impedance - Dielectric Constant I like to know if anyone found that Dielectric Constant, for the same material (e.g. FR-4), might be different when used for calculation of Microstrip or for calculation of Stripline. Avner Drory