diff --git a/sdrgui/gui/glspectrum.cpp b/sdrgui/gui/glspectrum.cpp
index e72863d4f..8192ef5b9 100644
--- a/sdrgui/gui/glspectrum.cpp
+++ b/sdrgui/gui/glspectrum.cpp
@@ -1178,6 +1178,7 @@ void GLSpectrum::drawMarkers()
 			{
 				ypoint.ry() =
 					(m_powerScale.getRangeMax() - m_currentSpectrum[m_histogramMarkers.at(i).m_fftBin]) / m_powerScale.getRange();
+				ypoint.ry() = ypoint.ry() > 1 ? 1 : ypoint.ry();
 				powerStr = displayScaledF(
 					m_currentSpectrum[m_histogramMarkers.at(i).m_fftBin],
 					m_linear ? 'e' : 'f',
@@ -1227,11 +1228,14 @@ void GLSpectrum::drawMarkers()
 				float poweri = m_histogramMarkers.at(i).m_markerType == SpectrumHistogramMarkerTypePower ?
 					m_currentSpectrum[m_histogramMarkers.at(i).m_fftBin] :
 					m_linear ? m_histogramMarkers.at(i).m_power : CalcDb::dbPower(m_histogramMarkers.at(i).m_power);
-				QString deltaPowerStr = displayScaledF(
-                            poweri - power0,
-                            m_linear ? 'e' : 'f',
-                            m_linear ? 3 : 1,
-                            false);
+				QString deltaPowerStr;
+
+				if (m_linear) {
+					deltaPowerStr = displayScaledF(poweri - power0, 'e', 3, false);
+				} else {
+					deltaPowerStr = QString::number(poweri - power0, 'f', 1);
+				}
+
                 drawTextOverlay(
                     m_histogramMarkers.at(i).m_deltaFrequencyStr,
                     QColor(255, 255, 255, 192),
diff --git a/sdrgui/gui/spectrummarkersdialog.cpp b/sdrgui/gui/spectrummarkersdialog.cpp
index 52f896c1a..8d7c2fbca 100644
--- a/sdrgui/gui/spectrummarkersdialog.cpp
+++ b/sdrgui/gui/spectrummarkersdialog.cpp
@@ -50,10 +50,11 @@ void SpectrumMarkersDialog::displayHistogramMarker()
 {
     if (m_histogramMarkers.size() == 0)
     {
-        ui->markerText->setText("-");
         ui->marker->setEnabled(false);
         ui->markerFrequency->setEnabled(false);
+        ui->powerMode->setEnabled(false);
         ui->fixedPower->setEnabled(false);
+        ui->markerText->setText("-");
         ui->fixedPower->setValue(0);
         ui->fixedPowerText->setText(tr("0.0"));
     }
@@ -61,10 +62,12 @@ void SpectrumMarkersDialog::displayHistogramMarker()
     {
         ui->marker->setEnabled(true);
         ui->markerFrequency->setEnabled(true);
+        ui->powerMode->setEnabled(true);
+        ui->fixedPower->setEnabled(true);
         ui->markerText->setText(tr("%1").arg(m_histogramMarkerIndex));
         ui->markerFrequency->setValue(m_histogramMarkers[m_histogramMarkerIndex].m_frequency);
+        ui->powerMode->setCurrentIndex((int) m_histogramMarkers[m_histogramMarkerIndex].m_markerType);
         float powerDB = CalcDb::dbPower(m_histogramMarkers[m_histogramMarkerIndex].m_power);
-        ui->fixedPower->setEnabled(true);
         ui->fixedPower->setValue(powerDB*10);
         ui->fixedPowerText->setText(QString::number(powerDB, 'f', 1));
     }
@@ -114,6 +117,21 @@ void SpectrumMarkersDialog::on_marker_valueChanged(int value)
     displayHistogramMarker();
 }
 
+void SpectrumMarkersDialog::on_setReference_clicked(bool checked)
+{
+    (void) checked;
+
+    if ((m_histogramMarkerIndex == 0) || (m_histogramMarkers.size() < 2)) {
+        return;
+    }
+
+    SpectrumHistogramMarker marker0 = m_histogramMarkers.at(0);
+    m_histogramMarkers[0] = m_histogramMarkers[m_histogramMarkerIndex];
+    m_histogramMarkers[m_histogramMarkerIndex] = marker0;
+    displayHistogramMarker();
+    m_histogramMarkersChanged = true;
+}
+
 void SpectrumMarkersDialog::on_markerAdd_clicked(bool checked)
 {
     (void) checked;
@@ -146,3 +164,13 @@ void SpectrumMarkersDialog::on_markerDel_clicked(bool checked)
     displayHistogramMarker();
     m_histogramMarkersChanged = true;
 }
+
+void SpectrumMarkersDialog::on_powerMode_currentIndexChanged(int index)
+{
+    if (m_histogramMarkers.size() == 0) {
+        return;
+    }
+
+    m_histogramMarkers[m_histogramMarkerIndex].m_markerType = (SpectrumHistogramMarkerType) index;
+    m_histogramMarkersChanged = true;
+}
diff --git a/sdrgui/gui/spectrummarkersdialog.h b/sdrgui/gui/spectrummarkersdialog.h
index 8a0e5150f..365e609aa 100644
--- a/sdrgui/gui/spectrummarkersdialog.h
+++ b/sdrgui/gui/spectrummarkersdialog.h
@@ -60,8 +60,10 @@ private slots:
     void on_markerFrequency_changed(qint64 value);
     void on_fixedPower_valueChanged(int value);
     void on_marker_valueChanged(int value);
+    void on_setReference_clicked(bool checked);
     void on_markerAdd_clicked(bool checked);
     void on_markerDel_clicked(bool checked);
+    void on_powerMode_currentIndexChanged(int index);
     void accept();
     void reject();
 };
diff --git a/sdrgui/gui/spectrummarkersdialog.ui b/sdrgui/gui/spectrummarkersdialog.ui
index f19440aed..1791c11c8 100644
--- a/sdrgui/gui/spectrummarkersdialog.ui
+++ b/sdrgui/gui/spectrummarkersdialog.ui
@@ -155,6 +155,22 @@
          </property>
         </widget>
        </item>
+       <item>
+        <widget class="QPushButton" name="setReference">
+         <property name="maximumSize">
+          <size>
+           <width>24</width>
+           <height>24</height>
+          </size>
+         </property>
+         <property name="toolTip">
+          <string>Set marker as reference (index 0)</string>
+         </property>
+         <property name="text">
+          <string>R</string>
+         </property>
+        </widget>
+       </item>
        <item>
         <layout class="QVBoxLayout" name="markerAddRemoveLayout">
          <property name="spacing">