diff --git a/amodem/detect.py b/amodem/detect.py
index 9fc81d3..66c9c19 100644
--- a/amodem/detect.py
+++ b/amodem/detect.py
@@ -85,12 +85,10 @@ class Detector(object):
         signal = np.concatenate([zeroes, carrier])
         signal = (2 ** 0.5) * signal / dsp.norm(signal)
 
-        coeffs = []
-        for i in range(len(buf) - len(signal)):
-            b = buf[i:i+len(signal)]
-            norm_b = dsp.norm(b)
-            c = (np.abs(np.dot(b, signal)) / norm_b) if norm_b else 0.0
-            coeffs.append(c)
+        corr = np.abs(np.correlate(buf, signal))
+        norm_b = np.sqrt(np.correlate(np.abs(buf)**2, np.ones(len(signal))))
+        coeffs = np.zeros_like(corr)
+        coeffs[norm_b > 0.0] = corr[norm_b > 0.0] / norm_b[norm_b > 0.0]
 
         index = np.argmax(coeffs)
         log.info('Carrier coherence: %.3f%%', coeffs[index] * 100)
diff --git a/amodem/equalizer.py b/amodem/equalizer.py
index 6f6e985..998801b 100644
--- a/amodem/equalizer.py
+++ b/amodem/equalizer.py
@@ -46,9 +46,9 @@ class Equalizer(object):
         return np.array(list(itertools.islice(symbols, size)))
 
 
-prefix = [1]*200 + [0]*50
 equalizer_length = 200
 silence_length = 50
+prefix = [1]*equalizer_length + [0]*silence_length
 
 
 def train(signal, expected, order, lookahead=0):
diff --git a/amodem/main.py b/amodem/main.py
index 8144903..fa7da27 100644
--- a/amodem/main.py
+++ b/amodem/main.py
@@ -59,7 +59,8 @@ def recv(config, src, dst, dump_audio=None, pylab=None):
         gain = 1.0 / amplitude
         log.debug('Gain correction: %.3f', gain)
 
-        sampler = sampling.Sampler(signal, sampling.Interpolator(), freq=freq)
+        sampler = sampling.Sampler(signal, sampling.defaultInterpolator,
+                                   freq=freq)
         receiver.run(sampler, gain=1.0/amplitude, output=dst)
         return True
     except BaseException:
diff --git a/amodem/recv.py b/amodem/recv.py
index 2544cdd..fb6404d 100644
--- a/amodem/recv.py
+++ b/amodem/recv.py
@@ -70,6 +70,7 @@ class Receiver(object):
         self.plt.plot(np.arange(order+lookahead), coeffs)
 
         equalization_filter = dsp.FIR(h=coeffs)
+        log.debug('Training completed')
         # Pre-load equalization filter with the signal (+lookahead)
         equalized = list(equalization_filter(signal))
         equalized = equalized[prefix+lookahead:-postfix+lookahead]
@@ -95,6 +96,7 @@ class Receiver(object):
             self._constellation(symbols[:, i], train_symbols[:, i],
                                 '$F_c = {0} Hz$'.format(freq), index=i)
         assert error_rate == 0, error_rate
+        log.debug('Training verified')
 
     def _bitstream(self, symbols, error_handler):
         streams = []
@@ -156,6 +158,7 @@ class Receiver(object):
         )
 
     def run(self, sampler, gain, output):
+        log.debug('Receiving')
         symbols = dsp.Demux(sampler, omegas=self.omegas, Nsym=self.Nsym)
         self._prefix(symbols, gain=gain)
 
diff --git a/amodem/sampling.py b/amodem/sampling.py
index b01ad4b..b369746 100644
--- a/amodem/sampling.py
+++ b/amodem/sampling.py
@@ -30,6 +30,9 @@ class Interpolator(object):
         assert len(self.filt) == resolution
 
 
+defaultInterpolator = Interpolator()
+
+
 class Sampler(object):
     def __init__(self, src, interp=None, freq=1.0):
         self.freq = freq