diff --git a/src/AppFrame.cpp b/src/AppFrame.cpp
index 03f02a5..5efd96d 100644
--- a/src/AppFrame.cpp
+++ b/src/AppFrame.cpp
@@ -358,7 +358,6 @@ AppFrame::AppFrame() :
     SetAcceleratorTable(accel);
 
     // frame rate = 1000 / 30 = 33ms
-    frame_timer.Start(33);
 //    static const int attribs[] = { WX_GL_RGBA, WX_GL_DOUBLEBUFFER, 0 };
 //    wxLogStatus("Double-buffered display %s supported", wxGLCanvas::IsDisplaySupported(attribs) ? "is" : "not");
 //    ShowFullScreen(true);
@@ -381,6 +380,10 @@ void AppFrame::initDeviceParams(std::string deviceId) {
     if (devConfig->getIQSwap()) {
         iqSwapMenuItem->Check();
     }
+    
+    if (!frame_timer.IsRunning()) {
+        frame_timer.Start(33);
+    }
 }
 
 
@@ -719,7 +722,8 @@ void AppFrame::OnTimer(wxTimerEvent& event) {
     } else {
         fftDistrib.setFFTSize(DEFAULT_FFT_SIZE);
     }
-    fftDistrib.setLinesPerSecond(60);
+    fftDistrib.setLinesPerSecond(24);
+    wxGetApp().getWaterfallVisualQueue()->set_max_num_items(24);
     fftDistrib.run();
 
     wproc->setView(waterfallCanvas->getViewState());
diff --git a/src/CubicSDR.cpp b/src/CubicSDR.cpp
index 51deb24..c6bbbe4 100644
--- a/src/CubicSDR.cpp
+++ b/src/CubicSDR.cpp
@@ -58,10 +58,10 @@ bool CubicSDR::OnInit() {
     spectrumDistributor.setInput(pipeIQVisualData);
     
     pipeDemodIQVisualData = new DemodulatorThreadInputQueue();
-    pipeIQVisualData->set_max_num_items(1);
+    pipeDemodIQVisualData->set_max_num_items(1);
     
     pipeSpectrumIQVisualData = new DemodulatorThreadInputQueue();
-    pipeIQVisualData->set_max_num_items(1);
+    pipeSpectrumIQVisualData->set_max_num_items(1);
     
     pipeWaterfallIQVisualData = new DemodulatorThreadInputQueue();
     pipeWaterfallIQVisualData->set_max_num_items(512);
diff --git a/src/sdr/SDRPostThread.cpp b/src/sdr/SDRPostThread.cpp
index 9baa1c7..4efc143 100644
--- a/src/sdr/SDRPostThread.cpp
+++ b/src/sdr/SDRPostThread.cpp
@@ -117,6 +117,7 @@ void SDRPostThread::run() {
             
             if (iqVisualQueue != NULL && iqVisualQueue->empty()) {
                 DemodulatorThreadIQData *visualDataOut = visualDataBuffers.getBuffer();
+                visualDataOut->busy_rw.lock();
                 visualDataOut->setRefCount(1);
                 
                 if (visualDataOut->data.size() < num_vis_samples) {
@@ -130,6 +131,7 @@ void SDRPostThread::run() {
                 visualDataOut->sampleRate = data_in->sampleRate;
                 visualDataOut->data.assign(dataOut.begin(), dataOut.begin() + num_vis_samples);
                 
+                visualDataOut->busy_rw.unlock();
                 iqVisualQueue->push(visualDataOut);
             }