diff --git a/mainwindow.cpp b/mainwindow.cpp
index f2defed..b2e5692 100644
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -33,6 +33,8 @@ MainWindow::MainWindow()
 
     plots = new PlotView();
     setCentralWidget(plots);
+
+    connect(dock, SIGNAL(fftSizeChanged(int)), plots, SLOT(setFFTSize(int)));
 }
 
 void MainWindow::openFile(QString fileName)
diff --git a/plotview.cpp b/plotview.cpp
index 6fd9d4d..fdb75a7 100644
--- a/plotview.cpp
+++ b/plotview.cpp
@@ -29,7 +29,6 @@
 #include "grsamplebuffer.h"
 #include "memory_sink.h"
 #include "memory_source.h"
-#include "spectrogramplot.h"
 #include "traceplot.h"
 
 PlotView::PlotView()
@@ -41,16 +40,16 @@ void PlotView::refreshSources()
 {
     plots.clear();
 
-    auto sp = new SpectrogramPlot(mainSampleSource);
-    plots.emplace_back(sp);
+    spectrogramPlot = new SpectrogramPlot(mainSampleSource);
+    plots.emplace_back(spectrogramPlot);
 
     gr::top_block_sptr iq_tb = gr::make_top_block("multiply");
     auto iq_mem_source = gr::blocks::memory_source::make(8);
     auto iq_mem_sink = gr::blocks::memory_sink::make(8);
     auto multiply = gr::blocks::multiply_const_cc::make(20);
-    if (selection) {
-        float centre = (selectionFreq.first + selectionFreq.second) / 2;
-        float cutoff = std::abs(selectionFreq.first - centre);
+    if (selection || true) {
+        float centre = -0.05; //(selectionFreq.first + selectionFreq.second) / 2;
+        float cutoff = 0.02; //std::abs(selectionFreq.first - centre);
         auto lp_taps = gr::filter::firdes::low_pass(1.0, 1.0, cutoff, cutoff / 2);
         auto filter = gr::filter::freq_xlating_fir_filter_ccf::make(1, lp_taps, centre, 1.0);
 
@@ -109,12 +108,19 @@ void PlotView::selectionCleared()
     refreshSources();
 }
 
+void PlotView::setFFTSize(int size)
+{
+    fftSize = size;
+    spectrogramPlot->setFFTSize(size);
+    viewport()->update();
+}
+
 void PlotView::paintEvent(QPaintEvent *event)
 {
     if (mainSampleSource == nullptr) return;
     off_t firstSample = horizontalScrollBar()->value();
     // TODO: don't hardcode width
-    off_t lastSample = firstSample + 10240;
+    off_t lastSample = firstSample + fftSize * width();
 
     QRect rect = QRect(0, 0, width(), height());
     QPainter painter(viewport());
diff --git a/plotview.h b/plotview.h
index 72ead19..ffa5ed2 100644
--- a/plotview.h
+++ b/plotview.h
@@ -23,6 +23,7 @@
 #include <QPaintEvent>
 #include "inputsource.h"
 #include "plot.h"
+#include "spectrogramplot.h"
 
 class PlotView : public QAbstractScrollArea
 {
@@ -35,16 +36,20 @@ public slots:
     void inputSourceChanged(AbstractSampleSource *input);
     void selectionChanged(std::pair<off_t, off_t> selectionTime, std::pair<float, float> selectionFreq);
     void selectionCleared();
+    void setFFTSize(int size);
 
 protected:
     void paintEvent(QPaintEvent *event);
 
 private:
     SampleSource<std::complex<float>> *mainSampleSource = nullptr;
+    SpectrogramPlot *spectrogramPlot;
     std::vector<std::unique_ptr<Plot>> plots;
     bool selection = false;
     std::pair<off_t, off_t> selectionTime;
     std::pair<float, float> selectionFreq;
 
+    int fftSize;
+
     void refreshSources();
 };
\ No newline at end of file