Avner--
         If I am wrong, I hope someone out there will make me smarter, but
   the dielectric "CONSTANT" is just that--constant for that type of material.
   IMOP, when calculating impedance of microstrip or stripline, the dielectric
   constant of a material doesn't change, less the material's unique tolerance
   range REF: IPC-D-275 Table 3-2. Therefore, unless proven wrong, the constant
   DOES NOT change, but the impedance value WILL vary depending on which 
   formula you are using depending on you pwb construction. Hope that helps.
   If wrong, please correct me via E-mail,

                             Bob Vanech
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