diff --git a/sdrbase/dsp/cwkeyer.cpp b/sdrbase/dsp/cwkeyer.cpp
index 8ea6f95e2..76b2cce0f 100644
--- a/sdrbase/dsp/cwkeyer.cpp
+++ b/sdrbase/dsp/cwkeyer.cpp
@@ -484,8 +484,11 @@ void CWSmoother::setNbFadeSamples(unsigned int nbFadeSamples)
 
         for (int i = 0; i < m_nbFadeSamples; i++)
         {
-            m_fadeInSamples[i] = sin((i/ (float) m_nbFadeSamples) * M_PI_2);
-            m_fadeOutSamples[i] = cos((i/ (float) m_nbFadeSamples) * M_PI_2);
+            float x = i/ (float) m_nbFadeSamples;
+            float y = 1.0f -x;
+
+            m_fadeInSamples[i] = smootherstep(x);
+            m_fadeOutSamples[i] = smootherstep(y);
         }
 
         m_fadeInCounter = 0;
@@ -530,3 +533,12 @@ bool CWSmoother::getFadeSample(bool on, float& sample)
         }
     }
 }
+
+float CWSmoother::smootherstep(float x)
+{
+    double x3 = x * x * x;
+    double x4 = x * x3;
+    double x5 = x * x4;
+
+    return (float) (6.0*x5 - 15.0*x4 + 10.0*x3);
+}
diff --git a/sdrbase/dsp/cwkeyer.h b/sdrbase/dsp/cwkeyer.h
index 7fcca31b0..a35dbf042 100644
--- a/sdrbase/dsp/cwkeyer.h
+++ b/sdrbase/dsp/cwkeyer.h
@@ -118,6 +118,8 @@ private:
     unsigned int m_nbFadeSamples;
     float *m_fadeInSamples;
     float *m_fadeOutSamples;
+
+    float smootherstep(float x);
 };
 
 #endif /* SDRBASE_DSP_CWKEYER_H_ */