diff --git a/FDTD/operator.cpp b/FDTD/operator.cpp
index 2fd1638..381f754 100644
--- a/FDTD/operator.cpp
+++ b/FDTD/operator.cpp
@@ -88,12 +88,11 @@ void Operator::Reset()
 	Operator::Init();
 }
 
-unsigned int Operator::GetNyquistNum(double fmax)
+unsigned int Operator::CalcNyquistNum(double fmax)
 {
 	if (dT==0) return 1;
 	double T0 = 1/fmax;
-	m_nyquistTS = floor(T0/2/dT);
-	return m_nyquistTS;
+	return floor(T0/2/dT);
 }
 
 bool Operator::SnapToMesh(double* dcoord, unsigned int* uicoord, bool lower)
@@ -245,7 +244,7 @@ unsigned int Operator::CalcGaussianPulsExcitation(double f0, double fc)
 		ExciteSignal[n] = cos(2.0*PI*f0*(n*dT-9.0/(2.0*PI*fc)))*exp(-1*pow(2.0*PI*fc*n*dT/3.0-3,2));
 //		cerr << ExciteSignal[n] << endl;
 	}
-	return GetNyquistNum(f0+fc);
+	return CalcNyquistNum(f0+fc);
 }
 
 unsigned int Operator::CalcDiracPulsExcitation()
@@ -259,10 +258,7 @@ unsigned int Operator::CalcDiracPulsExcitation()
 	ExciteSignal[0]=0.0;
 	ExciteSignal[1]=1.0;
 
-	// FIXME GetNyquistNum() has side-effects!
-	m_nyquistTS = 1;
-
-	return m_nyquistTS;
+	return 1;
 }
 
 unsigned int Operator::CalcStepExcitation()
@@ -275,10 +271,7 @@ unsigned int Operator::CalcStepExcitation()
 	ExciteSignal[0]=1.0;
 	ExciteSignal[1]=1.0;
 
-	// FIXME GetNyquistNum() has side-effects!
-	m_nyquistTS = 1;
-
-	return m_nyquistTS;
+	return 1;
 }
 
 unsigned int Operator::CalcSinusExcitation(double f0, int nTS)
@@ -296,7 +289,7 @@ unsigned int Operator::CalcSinusExcitation(double f0, int nTS)
 		ExciteSignal[n] = sin(2.0*PI*f0*n*dT);
 //		cerr << ExciteSignal[n] << endl;
 	}
-	return GetNyquistNum(f0);
+	return CalcNyquistNum(f0);
 }
 
 void Operator::DumpOperator2File(string filename)
diff --git a/FDTD/operator.h b/FDTD/operator.h
index 074fcc3..9ec8916 100644
--- a/FDTD/operator.h
+++ b/FDTD/operator.h
@@ -48,9 +48,12 @@ public:
 	virtual void ApplyMagneticBC(bool* dirs);
 
 	double GetTimestep() const {return dT;};
-	unsigned int GetNyquistNum(double fmax);
 	double GetNumberCells() const;
 
+	void SetNyquistNum(unsigned int nyquist) {m_nyquistTS=nyquist;}
+	unsigned int GetNyquistNum() const {return m_nyquistTS;};
+	unsigned int CalcNyquistNum(double fmax);
+
 	void ShowStat() const;
 
 	void DumpOperator2File(string filename);
diff --git a/openems.cpp b/openems.cpp
index 2beb857..6ec27dc 100644
--- a/openems.cpp
+++ b/openems.cpp
@@ -247,6 +247,8 @@ int openEMS::SetupFDTD(const char* file)
 		exit(-1);
 	}
 
+	FDTD_Op->SetNyquistNum(Nyquist);
+
 	if (DebugMat)
 	{
 		FDTD_Op->DumpMaterial2File("material_dump.vtk");