diff --git a/FDTD/operator.cpp b/FDTD/operator.cpp
index 7f7006e..f7b5588 100644
--- a/FDTD/operator.cpp
+++ b/FDTD/operator.cpp
@@ -731,18 +731,18 @@ bool Operator::CalcEFieldExcitation()
 	vector<unsigned int> vDelay;
 	vector<unsigned int> vDir;
 	unsigned int ipos;
-	int pos[3];
+	unsigned int pos[3];
 	double coord[3];
 	double delta[3];
 	double amp=0;
 
-	for (pos[2]=0;pos[2]<(int)numLines[2];++pos[2])
+	for (pos[2]=0;pos[2]<numLines[2];++pos[2])
 	{
 		delta[2]=fabs(MainOp->GetIndexDelta(2,pos[2]));
-		for (pos[1]=0;pos[1]<(int)numLines[1];++pos[1])
+		for (pos[1]=0;pos[1]<numLines[1];++pos[1])
 		{
 			delta[1]=fabs(MainOp->GetIndexDelta(1,pos[1]));
-			for (pos[0]=0;pos[0]<(int)numLines[0];++pos[0])
+			for (pos[0]=0;pos[0]<numLines[0];++pos[0])
 			{
 				delta[0]=fabs(MainOp->GetIndexDelta(0,pos[0]));
 				coord[0] = discLines[0][pos[0]];
@@ -759,7 +759,7 @@ bool Operator::CalcEFieldExcitation()
 						CSPropElectrode* elec = prop->ToElectrode();
 						if (elec!=NULL)
 						{
-							if ((elec->GetActiveDir(n)) && (pos[n]<(int)numLines[n]-1))
+							if ((elec->GetActiveDir(n)) && (pos[n]<numLines[n]-1))
 							{
 								amp = elec->GetWeightedExcitation(n,coord)*delta[n]*gridDelta;
 								if (amp!=0)
@@ -824,7 +824,7 @@ bool Operator::CalcEFieldExcitation()
 //						cerr << n << " " << coord[0] << " " << coord[1] << " " << coord[2] << endl;
 						if (elec!=NULL)
 						{
-							if ((elec->GetActiveDir(n)) && (pos[n]<(int)numLines[n]-1))
+							if ((elec->GetActiveDir(n)) && (pos[n]<numLines[n]-1))
 							{
 								amp = elec->GetWeightedExcitation(n,coord)*deltaN*gridDelta;
 								if (amp!=0)
diff --git a/FDTD/processfields.cpp b/FDTD/processfields.cpp
index 4c46261..ff70810 100644
--- a/FDTD/processfields.cpp
+++ b/FDTD/processfields.cpp
@@ -185,12 +185,13 @@ bool ProcessFields::DumpVectorArray2VTK(ofstream &file, string name, FDTD_FLOAT*
 {
 	WriteVTKHeader(file, discLines, numLines);
 	WriteVTKVectorArray(file, name, array, numLines);
+	return true;
 }
 
 bool ProcessFields::DumpMultiVectorArray2VTK(ofstream &file, string names[], FDTD_FLOAT**** array[], unsigned int numFields, double** discLines, unsigned int* numLines)
 {
 	WriteVTKHeader(file, discLines, numLines);
-	for (int n=0;n<numFields;++n)
+	for (unsigned int n=0;n<numFields;++n)
 	{
 		WriteVTKVectorArray(file, names[n], array[n], numLines);
 		file << endl;
diff --git a/openems.cpp b/openems.cpp
index a9eb635..dcad72b 100644
--- a/openems.cpp
+++ b/openems.cpp
@@ -131,7 +131,12 @@ int openEMS::SetupFDTD(const char* file)
 		cerr << "Can't read openEMS FDTD Settings... " << endl;
 		exit(-1);
 	}
-	FDTD_Opts->QueryIntAttribute("NumberOfTimesteps",&NrTS);
+	int help=0;
+	FDTD_Opts->QueryIntAttribute("NumberOfTimesteps",&help);
+	if (help<0)
+		NrTS=0;
+	else
+		NrTS = help;
 	FDTD_Opts->QueryDoubleAttribute("endCriteria",&endCrit);
 	if (endCrit==0)
 		endCrit=1e-6;
@@ -325,14 +330,14 @@ void openEMS::RunFDTD()
 	double t_diff;
 	//*************** simulate ************//
 	int step=PA->Process();
-	if ((step<0) || (step>NrTS)) step=NrTS;
+	if ((step<0) || (step>(int)NrTS)) step=NrTS;
 	while ((FDTD_Eng->GetNumberOfTimesteps()<NrTS) && (change>endCrit))
 	{
 		FDTD_Eng->IterateTS(step);
 		step=PA->Process();
 //		cout << " do " << step << " steps; current: " << eng.GetNumberOfTimesteps() << endl;
 		currTS = FDTD_Eng->GetNumberOfTimesteps();
-		if ((step<0) || (step>NrTS - currTS)) step=NrTS - currTS;
+		if ((step<0) || (step>(int)(NrTS - currTS))) step=NrTS - currTS;
 
 		gettimeofday(&currTime,NULL);
 
diff --git a/openems.h b/openems.h
index 73bc943..ca3378b 100644
--- a/openems.h
+++ b/openems.h
@@ -44,7 +44,7 @@ public:
 
 protected:
 	//! Number of Timesteps
-	int NrTS;
+	unsigned int NrTS;
 	bool Enable_Dumps;
 	bool DebugMat;
 	bool DebugOp;