Three dielectric values answer different questionsRogers PCB vs FR-4: an engineering comparison. Engineering illustration, not a production photograph or test result.Three dielectric values answer different questionsRogers PCB vs FR-4: an engineering comparisonProcess DkSupplier test methodMaterial controlDesign DkConstruction / methodCircuit model inputEffective DkLine + surroundingsPropagation resultKeep frequency, temperature, method and construction with each value.A test tolerance is not automatically a finished-circuit impedance tolerance.