diff --git a/vna_qt/mainwindow.C b/vna_qt/mainwindow.C
index 4c11b53..825682f 100644
--- a/vna_qt/mainwindow.C
+++ b/vna_qt/mainwindow.C
@@ -403,22 +403,23 @@ void MainWindow::updatePortExtension() {
 
 static string calFileVer = "calFileVersion 1";
 string MainWindow::serializeCalibration(const CalibrationInfo &cal) {
+    scopedCLocale _locale; // use standard number formatting
     string tmp;
     tmp.append(calFileVer);
     tmp += '\n';
     tmp.append(cal.calName + "\n");
-    tmp.append(to_string(cal.nPoints)+" "+to_string(cal.startFreqHz)+" "+to_string(cal.stepFreqHz));
-    tmp.append(" "+to_string(cal.attenuation1)+" "+to_string(cal.attenuation2));
+    saprintf(tmp, "%d %f %f ", cal.nPoints, cal.startFreqHz, cal.stepFreqHz);
+    saprintf(tmp, "%d %d", cal.attenuation1, cal.attenuation2);
     tmp += '\n';
     for(auto& calstd:cal.measurements) {
+        if(calstd.first.length() == 0)
+            continue;
         tmp.append(calstd.first);
         tmp += '\n';
         for(const VNARawValue& val:calstd.second) {
             int sz=val.rows()*val.cols();
             for(int i=0;i<sz;i++) {
-                tmp.append(to_string(val(i).real()) + " ");
-                tmp.append(to_string(val(i).imag()));
-                tmp += ' ';
+                saprintf(tmp, "%f %f ", val(i).real(), val(i).imag());
             }
             tmp += '\n';
         }
@@ -427,6 +428,7 @@ string MainWindow::serializeCalibration(const CalibrationInfo &cal) {
 }
 
 CalibrationInfo MainWindow::deserializeCalibration(QTextStream &inp) {
+    scopedCLocale _locale; // use standard number formatting
     CalibrationInfo ret;
     string versionStr = inp.readLine().toStdString();
     if(versionStr != calFileVer) {
@@ -453,6 +455,9 @@ CalibrationInfo MainWindow::deserializeCalibration(QTextStream &inp) {
             }
             values.push_back(value);
         }
+        // discard the rest of the line
+        inp.readLine();
+
         ret.measurements[calstd.toStdString()] = values;
         fprintf(stderr, "found cal standard %s\n", calstd.toUtf8().data());
         fflush(stderr);
diff --git a/vna_qt/touchstone.C b/vna_qt/touchstone.C
index ae57492..02a3804 100644
--- a/vna_qt/touchstone.C
+++ b/vna_qt/touchstone.C
@@ -9,34 +9,10 @@
 
 using namespace std;
 
-#if __cplusplus < 201103L
-  #error This library needs at least a C++11 compliant compiler
-#endif
-
-// append to dst
-int saprintf(string& dst, const char* fmt, ...) {
-    int bytesToAllocate=32;
-    int originalLen=dst.length();
-    while(true) {
-        dst.resize(originalLen+bytesToAllocate);
-        va_list args;
-        va_start(args, fmt);
-        // ONLY WORKS WITH C++11!!!!!!!!
-        // .data() does not guarantee enough space for the null byte before c++11
-        int len = vsnprintf((char*)dst.data()+originalLen, bytesToAllocate+1, fmt, args);
-        va_end(args);
-        if(len>=0 && len <= bytesToAllocate) {
-            dst.resize(originalLen+len);
-            return len;
-        }
-        if(len<=0) bytesToAllocate*=2;
-        else bytesToAllocate = len;
-    }
-}
-
 
 
 string serializeTouchstone(vector<complex<double> > data, double startFreqHz, double stepFreqHz) {
+    scopedCLocale _locale; // use standard number formatting
     string res;
     res += "# MHz S MA R 50\n";
     saprintf(res,"!   freq        S11       \n");
@@ -52,6 +28,7 @@ string serializeTouchstone(vector<complex<double> > data, double startFreqHz, do
 }
 
 string serializeTouchstone(vector<Matrix2cd> data, double startFreqHz, double stepFreqHz) {
+    scopedCLocale _locale; // use standard number formatting
     string res;
     res += "# MHz S MA R 50\n";
     saprintf(res,"!   freq        S11              S21              S12              S22       \n");
@@ -72,6 +49,7 @@ string serializeTouchstone(vector<Matrix2cd> data, double startFreqHz, double st
 
 
 void parseTouchstone(string data, int& nPorts, map<double, MatrixXcd> &results) {
+    scopedCLocale _locale; // use standard number formatting
     istringstream iss(data);
     string line;
 
diff --git a/vna_qt/utility.H b/vna_qt/utility.H
index 174d320..77a1272 100644
--- a/vna_qt/utility.H
+++ b/vna_qt/utility.H
@@ -9,9 +9,31 @@
 #include <sstream>
 #include <QString>
 #include <time.h>
+#include <locale.h>
+
+
+#if __cplusplus < 201103L
+  #error This library needs at least a C++11 compliant compiler
+#endif
 
 using namespace std;
 
+// when this class is instantiated, the program locale is set to C
+class scopedCLocale {
+public:
+    bool _shouldRevert = true;
+    scopedCLocale() {
+        if(strcmp("C", setlocale(LC_ALL, NULL)) == 0)
+            _shouldRevert = false;
+        setlocale(LC_ALL, "C");
+    }
+    ~scopedCLocale() {
+        if(_shouldRevert)
+            setlocale(LC_ALL, "");
+    }
+};
+
+
 inline QString qs(const string& s) {
     return QString::fromStdString(s);
 }
@@ -74,6 +96,28 @@ inline string ssprintf(int maxLen, const char* fmt, ...) {
     tmp.resize(len);
     return tmp;
 }
+
+// append to dst
+inline int saprintf(string& dst, const char* fmt, ...) {
+    int bytesToAllocate=32;
+    int originalLen=dst.length();
+    while(true) {
+        dst.resize(originalLen+bytesToAllocate);
+        va_list args;
+        va_start(args, fmt);
+        // ONLY WORKS WITH C++11!!!!!!!!
+        // .data() does not guarantee enough space for the null byte before c++11
+        int len = vsnprintf((char*)dst.data()+originalLen, bytesToAllocate+1, fmt, args);
+        va_end(args);
+        if(len>=0 && len <= bytesToAllocate) {
+            dst.resize(originalLen+len);
+            return len;
+        }
+        if(len<=0) bytesToAllocate*=2;
+        else bytesToAllocate = len;
+    }
+}
+
 inline string sstrftime(const char *format, const struct tm &tm) {
     char buf[256] = {0};
     strftime(buf, 256, format, &tm);