diff --git a/sdrbase/dsp/glspectruminterface.h b/sdrbase/dsp/glspectruminterface.h
index c8cd56307..35f844bd5 100644
--- a/sdrbase/dsp/glspectruminterface.h
+++ b/sdrbase/dsp/glspectruminterface.h
@@ -26,7 +26,7 @@ class GLSpectrumInterface
 public:
     GLSpectrumInterface() {}
     virtual ~GLSpectrumInterface() {}
-    virtual void newSpectrum(const std::vector<Real>& spectrum, int fftSize)
+    virtual void newSpectrum(const Real* spectrum, int fftSize)
     {
         (void) spectrum;
         (void) fftSize;
diff --git a/sdrbase/dsp/spectrumvis.cpp b/sdrbase/dsp/spectrumvis.cpp
index 78762d7de..bbf818f87 100644
--- a/sdrbase/dsp/spectrumvis.cpp
+++ b/sdrbase/dsp/spectrumvis.cpp
@@ -44,6 +44,7 @@ MESSAGE_CLASS_DEFINITION(SpectrumVis::MsgConfigureScalingFactor, Message)
 MESSAGE_CLASS_DEFINITION(SpectrumVis::MsgConfigureWSpectrumOpenClose, Message)
 MESSAGE_CLASS_DEFINITION(SpectrumVis::MsgConfigureWSpectrum, Message)
 MESSAGE_CLASS_DEFINITION(SpectrumVis::MsgStartStop, Message)
+MESSAGE_CLASS_DEFINITION(SpectrumVis::MsgFrequencyZooming, Message)
 
 const Real SpectrumVis::m_mult = (10.0f / log2(10.0f));
 
@@ -57,6 +58,8 @@ SpectrumVis::SpectrumVis(Real scalef) :
     m_psd(MAX_FFT_SIZE),
 	m_fftBufferFill(0),
 	m_needMoreSamples(false),
+    m_frequencyZoomFactor(1.0f),
+    m_frequencyZoomPos(0.5f),
 	m_scalef(scalef),
 	m_glSpectrum(nullptr),
     m_specMax(0.0f),
@@ -121,6 +124,10 @@ void SpectrumVis::feed(const Complex *begin, unsigned int length)
 
     Complex c;
     Real v;
+    int fftMin = (m_frequencyZoomFactor == 1.0f) ?
+        0 : (m_frequencyZoomPos - (0.5f / m_frequencyZoomFactor)) * m_settings.m_fftSize;
+    int fftMax = (m_frequencyZoomFactor == 1.0f) ?
+        m_settings.m_fftSize : (m_frequencyZoomPos - (0.5f / m_frequencyZoomFactor)) * m_settings.m_fftSize;
 
     if (m_settings.m_averagingMode == GLSpectrumSettings::AvgModeNone)
     {
@@ -140,7 +147,7 @@ void SpectrumVis::feed(const Complex *begin, unsigned int length)
 
         // send new data to visualisation
         if (m_glSpectrum) {
-            m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+            m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
         }
 
         // web socket spectrum connections
@@ -176,7 +183,7 @@ void SpectrumVis::feed(const Complex *begin, unsigned int length)
 
         // send new data to visualisation
         if (m_glSpectrum) {
-            m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+            m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
         }
 
         // web socket spectrum connections
@@ -223,7 +230,7 @@ void SpectrumVis::feed(const Complex *begin, unsigned int length)
         {
             // send new data to visualisation
             if (m_glSpectrum) {
-                m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+                m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
             }
 
             // web socket spectrum connections
@@ -269,7 +276,7 @@ void SpectrumVis::feed(const Complex *begin, unsigned int length)
         {
             // send new data to visualisation
             if (m_glSpectrum) {
-                m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+                m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
             }
 
             // web socket spectrum connections
@@ -374,7 +381,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 
                 // send new data to visualisation
                 if (m_glSpectrum) {
-                    m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+                    m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
                 }
 
                 // web socket spectrum connections
@@ -433,7 +440,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 
 	            // send new data to visualisation
                 if (m_glSpectrum) {
-    	            m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+    	            m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
                 }
 
                 // web socket spectrum connections
@@ -512,7 +519,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 
                     // send new data to visualisation
                     if (m_glSpectrum) {
-                        m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+                        m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
                     }
 
                     // web socket spectrum connections
@@ -590,7 +597,7 @@ void SpectrumVis::feed(const SampleVector::const_iterator& cbegin, const SampleV
 
                     // send new data to visualisation
                     if (m_glSpectrum) {
-                        m_glSpectrum->newSpectrum(m_powerSpectrum, m_settings.m_fftSize);
+                        m_glSpectrum->newSpectrum(m_powerSpectrum.data(), m_settings.m_fftSize);
                     }
 
                     // web socket spectrum connections
@@ -694,7 +701,13 @@ bool SpectrumVis::handleMessage(const Message& message)
     {
         MsgStartStop& cmd = (MsgStartStop&) message;
         setRunning(cmd.getStartStop());
-
+        return true;
+    }
+    else if (MsgFrequencyZooming::match(message))
+    {
+        MsgFrequencyZooming& cmd = (MsgFrequencyZooming&) message;
+        m_frequencyZoomFactor = cmd.getFrequencyZoomFactor();
+        m_frequencyZoomPos = cmd.getFrequencyZoomPos();
         return true;
     }
 	else
diff --git a/sdrbase/dsp/spectrumvis.h b/sdrbase/dsp/spectrumvis.h
index 10cd73c0f..9b0ed80f1 100644
--- a/sdrbase/dsp/spectrumvis.h
+++ b/sdrbase/dsp/spectrumvis.h
@@ -107,6 +107,28 @@ public:
         {}
     };
 
+    class MsgFrequencyZooming : public Message {
+        MESSAGE_CLASS_DECLARATION
+
+    public:
+        float getFrequencyZoomFactor() const { return m_frequencyZoomFactor; }
+        float getFrequencyZoomPos() const { return m_frequencyZoomPos; }
+
+        static MsgFrequencyZooming* create(float frequencyZoomFactor, float frequencyZoomPos) {
+            return new MsgFrequencyZooming(frequencyZoomFactor, frequencyZoomPos);
+        }
+
+    private:
+        float m_frequencyZoomFactor;
+        float m_frequencyZoomPos;
+
+        MsgFrequencyZooming(float frequencyZoomFactor, float frequencyZoomPos) :
+            Message(),
+            m_frequencyZoomFactor(frequencyZoomFactor),
+            m_frequencyZoomPos(frequencyZoomPos)
+        { }
+    };
+
     enum AvgMode
     {
         AvgModeNone,
@@ -198,6 +220,9 @@ private:
 	int m_fftBufferFill;
 	bool m_needMoreSamples;
 
+    float m_frequencyZoomFactor;
+    float m_frequencyZoomPos;
+
 	Real m_scalef;
 	GLSpectrumInterface* m_glSpectrum;
     WSSpectrum m_wsSpectrum;
diff --git a/sdrgui/gui/glspectrum.cpp b/sdrgui/gui/glspectrum.cpp
index ebf7b8d73..66e599732 100644
--- a/sdrgui/gui/glspectrum.cpp
+++ b/sdrgui/gui/glspectrum.cpp
@@ -25,6 +25,7 @@
 #include <QOpenGLFunctions>
 #include <QPainter>
 #include <QFontDatabase>
+#include "dsp/spectrumvis.h"
 #include "gui/glspectrum.h"
 #include "util/messagequeue.h"
 
@@ -33,10 +34,13 @@
 MESSAGE_CLASS_DEFINITION(GLSpectrum::MsgReportSampleRate, Message)
 MESSAGE_CLASS_DEFINITION(GLSpectrum::MsgReportWaterfallShare, Message)
 
+const float GLSpectrum::m_maxFrequencyZoom = 4.0f;
+
 GLSpectrum::GLSpectrum(QWidget* parent) :
 	QGLWidget(parent),
 	m_cursorState(CSNormal),
     m_cursorChannel(0),
+	m_spectrumVis(nullptr),
 	m_fpsPeriodMs(50),
 	m_mouseInside(false),
 	m_changesPending(true),
@@ -159,6 +163,7 @@ GLSpectrum::GLSpectrum(QWidget* parent) :
     m_textOverlayFont = font(); // QFontDatabase::systemFont(QFontDatabase::FixedFont);
     m_textOverlayFont.setBold(true);
     // m_textOverlayFont.setPointSize(font().pointSize() - 1);
+	resetFrequencyZoom();
 
 	m_timer.setTimerType(Qt::PreciseTimer);
 	connect(&m_timer, SIGNAL(timeout()), this, SLOT(tick()));
@@ -408,7 +413,7 @@ void GLSpectrum::removeChannelMarker(ChannelMarker* channelMarker)
 	m_mutex.unlock();
 }
 
-void GLSpectrum::newSpectrum(const std::vector<Real>& spectrum, int fftSize)
+void GLSpectrum::newSpectrum(const Real *spectrum, int fftSize)
 {
 	QMutexLocker mutexLocker(&m_mutex);
 
@@ -435,7 +440,7 @@ void GLSpectrum::newSpectrum(const std::vector<Real>& spectrum, int fftSize)
 	}
 }
 
-void GLSpectrum::updateWaterfall(const std::vector<Real>& spectrum)
+void GLSpectrum::updateWaterfall(const Real *spectrum)
 {
 	if (m_waterfallBufferPos < m_waterfallBuffer->height())
     {
@@ -458,7 +463,7 @@ void GLSpectrum::updateWaterfall(const std::vector<Real>& spectrum)
 	}
 }
 
-void GLSpectrum::updateHistogram(const std::vector<Real>& spectrum)
+void GLSpectrum::updateHistogram(const Real *spectrum)
 {
 	quint8* b = m_histogram;
 	int fftMulSize = 100 * m_fftSize;
@@ -484,7 +489,7 @@ void GLSpectrum::updateHistogram(const std::vector<Real>& spectrum)
 		}
 	}
 
-	m_currentSpectrum = &spectrum; // Store spectrum for current spectrum line display
+	m_currentSpectrum = spectrum; // Store spectrum for current spectrum line display
 
 #if 0 //def USE_SSE2
     if(m_decay >= 0) { // normal
@@ -963,7 +968,7 @@ void GLSpectrum::paintGL()
 
 			for (int i = 0; i < m_fftSize; i++)
 			{
-				Real v = (*m_currentSpectrum)[i] - m_referenceLevel;
+				Real v = m_currentSpectrum[i] - m_referenceLevel;
 
 				if (v > 0) {
 				    v = 0;
@@ -2193,16 +2198,73 @@ void GLSpectrum::mouseReleaseEvent(QMouseEvent*)
 
 void GLSpectrum::wheelEvent(QWheelEvent *event)
 {
-    int mul;
-
     if (event->modifiers() & Qt::ShiftModifier) {
-        mul = 100;
+		channelMarkerMove(event, 100);
     } else if (event->modifiers() & Qt::ControlModifier) {
-        mul = 10;
+		channelMarkerMove(event, 10);
+    } else if (event->modifiers() & Qt::AltModifier) {
+		frequencyZoom(event);
     } else {
-        mul = 1;
+        channelMarkerMove(event, 1);
     }
+}
 
+void GLSpectrum::frequencyZoom(QWheelEvent *event)
+{
+	const QPointF& p = event->position();
+
+	if (event->delta() > 0) // zoom in
+	{
+		if (m_frequencyZoomFactor < m_maxFrequencyZoom) {
+			m_frequencyZoomFactor += 0.5f;
+		}
+	}
+	else
+	{
+		if (m_frequencyZoomFactor > 1.0f) {
+			m_frequencyZoomFactor -= 0.5f;
+		}
+	}
+
+	float pw = (p.x() - m_leftMargin) / (width() - m_leftMargin - m_rightMargin); // position in window
+	pw = pw < 0.0f ? 0.0f : pw > 1.0f ? 1.0 : pw;
+	m_frequencyZoomPos += (pw - 0.5f) * (1.0f / m_frequencyZoomFactor);
+	float lim = 0.5f / m_frequencyZoomFactor;
+	m_frequencyZoomPos = m_frequencyZoomPos < lim ? lim : m_frequencyZoomPos > 1 - lim ? 1 - lim : m_frequencyZoomPos;
+
+	updateFFTLimits();
+	qDebug("GLSpectrum::spectrumZoom: pw: %f p: %f z: %f", pw, m_frequencyZoomPos, m_frequencyZoomFactor);
+}
+
+void GLSpectrum::resetFrequencyZoom()
+{
+	m_frequencyZoomFactor = 1.0f;
+	m_frequencyZoomPos = 0.5f;
+
+	updateFFTLimits();
+}
+
+void GLSpectrum::updateFFTLimits()
+{
+	if (!m_spectrumVis) {
+		return;
+	}
+
+	SpectrumVis::MsgFrequencyZooming *msg = SpectrumVis::MsgFrequencyZooming::create(
+		m_frequencyZoomFactor, m_frequencyZoomPos
+	);
+
+	m_spectrumVis->getInputMessageQueue()->push(msg);
+}
+
+// void GLSpectrum::updateFFTLimits()
+// {
+// 	m_fftMin = m_frequencyZoomFactor == 1 ? 0 : (m_frequencyZoomPos - (0.5f / m_frequencyZoomFactor)) * m_fftSize;
+// 	m_fftMax = m_frequencyZoomFactor == 1 ? m_fftSize : (m_frequencyZoomPos - (0.5f / m_frequencyZoomFactor)) * m_fftSize;
+// }
+
+void GLSpectrum::channelMarkerMove(QWheelEvent *event, int mul)
+{
     for (int i = 0; i < m_channelMarkerStates.size(); ++i)
     {
         if ((m_channelMarkerStates[i]->m_channelMarker->getSourceOrSinkStream() != m_displaySourceOrSink)
diff --git a/sdrgui/gui/glspectrum.h b/sdrgui/gui/glspectrum.h
index 35782210b..a61292cbd 100644
--- a/sdrgui/gui/glspectrum.h
+++ b/sdrgui/gui/glspectrum.h
@@ -39,6 +39,7 @@
 
 class QOpenGLShaderProgram;
 class MessageQueue;
+class SpectrumVis;
 
 class SDRGUI_API GLSpectrum : public QGLWidget, public GLSpectrumInterface {
 	Q_OBJECT
@@ -103,7 +104,7 @@ public:
 	void removeChannelMarker(ChannelMarker* channelMarker);
 	void setMessageQueueToGUI(MessageQueue* messageQueue) { m_messageQueueToGUI = messageQueue; }
 
-	virtual void newSpectrum(const std::vector<Real>& spectrum, int fftSize);
+	virtual void newSpectrum(const Real* spectrum, int fftSize);
 	void clearSpectrumHistogram();
 
 	Real getWaterfallShare() const { return m_waterfallShare; }
@@ -115,6 +116,7 @@ public:
         m_displaySourceOrSink = sourceOrSink;
         m_displayStreamIndex = streamIndex;
     }
+    void setSpectrumVis(SpectrumVis *spectrumVis) { m_spectrumVis = spectrumVis; }
 
 private:
 	struct ChannelMarkerState {
@@ -235,6 +237,7 @@ private:
 	CursorState m_cursorState;
 	int m_cursorChannel;
 
+    SpectrumVis* m_spectrumVis;
 	QTimer m_timer;
     int m_fpsPeriodMs;
 	QMutex m_mutex;
@@ -259,7 +262,7 @@ private:
 
 	std::vector<Real> m_maxHold;
 	bool m_displayMaxHold;
-	const std::vector<Real> *m_currentSpectrum;
+	const Real *m_currentSpectrum;
 	bool m_displayCurrent;
 
 	Real m_waterfallShare;
@@ -305,6 +308,9 @@ private:
 	bool m_displayChanged;
     bool m_displaySourceOrSink;
     int m_displayStreamIndex;
+    float m_frequencyZoomFactor;
+    float m_frequencyZoomPos;
+    static const float m_maxFrequencyZoom;
 
 	GLShaderSimple m_glShaderSimple;
 	GLShaderTextured m_glShaderLeftScale;
@@ -321,10 +327,8 @@ private:
 
 	MessageQueue *m_messageQueueToGUI;
 
-	static const int m_waterfallBufferHeight = 256;
-
-	void updateWaterfall(const std::vector<Real>& spectrum);
-	void updateHistogram(const std::vector<Real>& spectrum);
+	void updateWaterfall(const Real *spectrum);
+	void updateHistogram(const Real *spectrum);
 
 	void initializeGL();
 	void resizeGL(int width, int height);
@@ -338,6 +342,10 @@ private:
 	void mousePressEvent(QMouseEvent* event);
 	void mouseReleaseEvent(QMouseEvent* event);
     void wheelEvent(QWheelEvent*);
+    void channelMarkerMove(QWheelEvent*, int mul);
+    void frequencyZoom(QWheelEvent*);
+    void resetFrequencyZoom();
+    void updateFFTLimits();
 
 	void enterEvent(QEvent* event);
 	void leaveEvent(QEvent* event);
diff --git a/sdrgui/gui/glspectrumgui.cpp b/sdrgui/gui/glspectrumgui.cpp
index b8c6bba0c..fdd5c3d71 100644
--- a/sdrgui/gui/glspectrumgui.cpp
+++ b/sdrgui/gui/glspectrumgui.cpp
@@ -77,6 +77,7 @@ void GLSpectrumGUI::setBuddies(SpectrumVis* spectrumVis, GLSpectrum* glSpectrum)
 {
 	m_spectrumVis = spectrumVis;
 	m_glSpectrum = glSpectrum;
+    m_glSpectrum->setSpectrumVis(spectrumVis);
 	m_glSpectrum->setMessageQueueToGUI(&m_messageQueue);
     m_spectrumVis->setMessageQueueToGUI(&m_messageQueue);
 }