diff --git a/Software/PC_Application/Calibration/calibration.cpp b/Software/PC_Application/Calibration/calibration.cpp
index 655f7ad..312be66 100644
--- a/Software/PC_Application/Calibration/calibration.cpp
+++ b/Software/PC_Application/Calibration/calibration.cpp
@@ -709,7 +709,7 @@ bool Calibration::openFromFile(QString filename)
         qWarning() << "Calibration file parsing failed: " << e.what();
         return false;
     }
-    this->currentCalFile = filename;    // if all ok, remember this and show on widget
+    this->currentCalFile = filename;    // if all ok, remember this
 
     return true;
 }
@@ -717,7 +717,7 @@ bool Calibration::openFromFile(QString filename)
 bool Calibration::saveToFile(QString filename)
 {
     if(filename.isEmpty()) {
-        // suggest descriptive name
+        // Suggest descriptive name ie. "SOLT 40M-700M 1000pt"
         QString fn = Calibration::TypeToString(this->getType())
                 + " "
                 + hzToString(minFreq) + "-" + hzToString(maxFreq)
@@ -742,7 +742,7 @@ bool Calibration::saveToFile(QString filename)
     auto calkit_file = filename + ".calkit";
     qDebug() << "Saving associated calibration kit to file" << calkit_file;
     kit.toFile(calkit_file);
-    this->currentCalFile = calibration_file;        // if all ok, remember this and show on widget
+    this->currentCalFile = calibration_file;    // if all ok, remember this
 
     return true;
 }
@@ -750,7 +750,7 @@ bool Calibration::saveToFile(QString filename)
 /**
  * @brief Calibration::hzToString
  * @param freqHz - input frequency in Hz
- * @return frequency in human-readable form such as 145k 2M, 2.1M, 3.45G
+ * @return frequency in human-friendly form such as 145k 2M, 2.1M, 3.45G
  */
 QString Calibration::hzToString(double freqHz){
     int dgt = 3;        // how many significant digits
diff --git a/Software/PC_Application/VNA/vna.cpp b/Software/PC_Application/VNA/vna.cpp
index c4cb26a..8d41d61 100644
--- a/Software/PC_Application/VNA/vna.cpp
+++ b/Software/PC_Application/VNA/vna.cpp
@@ -287,7 +287,7 @@ VNA::VNA(AppWindow *window)
 
     // Calibration toolbar (and populate calibration menu)
     auto tb_cal = new QToolBar("Calibration");
-    QLabel *cbEnableCal_label = new QLabel("Calibration:");
+    QLabel *cbEnableCal_label = new QLabel("Calibration:");     // correct object type
     tb_cal->addWidget(cbEnableCal_label);
     auto cbEnableCal = new QCheckBox;
     tb_cal->addWidget(cbEnableCal);
@@ -327,8 +327,8 @@ VNA::VNA(AppWindow *window)
         cbEnableCal->blockSignals(true);
         calDisable->setChecked(true);
         cbEnableCal->setCheckState(Qt::CheckState::Unchecked);
-        cbEnableCal_label->setStyleSheet("background-color: yellow");
-        cbEnableCal_label->setToolTip("none");
+        cbEnableCal_label->setStyleSheet("background-color: yellow");       // visually indicate loss of calibration
+        cbEnableCal_label->setToolTip("none");                              // cal. file unknown at this moment
         cbType->blockSignals(false);
         cbEnableCal->blockSignals(false);
         calImportTerms->setEnabled(false);
@@ -346,8 +346,8 @@ VNA::VNA(AppWindow *window)
             }
         }
         cbEnableCal->setCheckState(Qt::CheckState::Checked);
-        cbEnableCal_label->setStyleSheet("");
-        cbEnableCal_label->setToolTip(cal.getCurrentCalibrationFile());
+        cbEnableCal_label->setStyleSheet("");                               // restore default look of widget
+        cbEnableCal_label->setToolTip(cal.getCurrentCalibrationFile());     // on hover, show name of active cal. file
         cbType->blockSignals(false);
         cbEnableCal->blockSignals(false);
         calImportTerms->setEnabled(true);
diff --git a/Software/PC_Application/preferences.cpp b/Software/PC_Application/preferences.cpp
index 6ca99dd..d1bc3b0 100644
--- a/Software/PC_Application/preferences.cpp
+++ b/Software/PC_Application/preferences.cpp
@@ -163,6 +163,11 @@ void PreferencesDialog::setInitialGUIState()
     ui->GeneralGraphBackground->setColor(p->General.graphColors.background);
     ui->GeneralGraphAxis->setColor(p->General.graphColors.axis);
     ui->GeneralGraphDivisions->setColor(p->General.graphColors.divisions);
+
+    QTreeWidgetItem *item = ui->treeWidget->topLevelItem(0);
+    if (item != nullptr) {
+        ui->treeWidget->setCurrentItem(item);     // visually select first item
+    }
 }
 
 void Preferences::load()