diff --git a/drift.py b/drift.py
index 77f267b..64eb602 100644
--- a/drift.py
+++ b/drift.py
@@ -3,11 +3,12 @@ import numpy as np
 import recv
 import common
 import sigproc
+import sampling
 import loop
 
 class FreqLoop(object):
     def __init__(self, x, freq):
-        self.sampler = sigproc.Sampler(x, sigproc.Interpolator())
+        self.sampler = sampling.Sampler(x, sampling.Interpolator())
         self.symbols = recv.extract_symbols(self.sampler, freq)
         Kp, Ki = 0.2, 0.01
         b = np.array([1, -1])*Kp + np.array([0.5, 0.5])*Ki
@@ -26,8 +27,6 @@ class FreqLoop(object):
 import pylab
 
 def main():
-    import sigproc
-
     f0 = 10e3
     _, x = common.load('recv_10kHz.pcm')
     x = x[100:]
diff --git a/sampling.py b/sampling.py
new file mode 100644
index 0000000..2b9d75c
--- /dev/null
+++ b/sampling.py
@@ -0,0 +1,58 @@
+import numpy as np
+
+class Interpolator(object):
+    def __init__(self, resolution=10000, width=128):
+        self.width = width
+        self.resolution = resolution
+        self.N = resolution * width
+        u = np.arange(-self.N, self.N, dtype=float)
+        window = (1 + np.cos(0.5 * np.pi * u / self.N)) / 2.0
+        h = np.sinc(u / resolution) * window
+        self.filt = []
+        for index in range(resolution):  # split into multiphase filters
+            filt = h[index::resolution]
+            filt = filt[::-1]
+            self.filt.append(filt)
+        lengths = map(len, self.filt)
+        assert set(lengths) == set([2*width])
+        assert len(self.filt) == resolution
+
+    def get(self, offset):
+        # offset = k + (j / self.resolution)
+        k = int(offset)
+        j = int((offset - k) * self.resolution)
+        coeffs = self.filt[j]
+        return coeffs, k - self.width
+
+class Sampler(object):
+    def __init__(self, src, interp):
+        self.src = iter(src)
+        self.freq = 1.0
+        self.interp = interp
+        coeffs, begin = self.interp.get(0)
+        self.offset = -begin  # should fill samples buffer
+        self.buff = np.zeros(len(coeffs))
+        self.index = 0
+
+    def __iter__(self):
+        return self
+
+    def correct(self, offset=0):
+        assert self.freq + offset > 0
+        self.offset += offset
+
+    def next(self):
+        res = self._sample()
+        self.offset += self.freq
+        return res
+
+    def _sample(self):
+        coeffs, begin = self.interp.get(self.offset)
+        end = begin + len(coeffs)
+        while True:
+            if self.index == end:
+                return np.dot(coeffs, self.buff)
+
+            self.buff[:-1] = self.buff[1:]
+            self.buff[-1] = self.src.next()  # throws StopIteration
+            self.index += 1
diff --git a/sigproc.py b/sigproc.py
index 5d1e6ed..606d804 100644
--- a/sigproc.py
+++ b/sigproc.py
@@ -52,62 +52,5 @@ class QAM(object):
 
 modulator = QAM(bits_per_symbol=2, radii=[1.0])
 
-class Interpolator(object):
-    def __init__(self, resolution=10000, width=128):
-        self.width = width
-        self.resolution = resolution
-        self.N = resolution * width
-        u = np.arange(-self.N, self.N, dtype=float)
-        window = (1 + np.cos(0.5 * np.pi * u / self.N)) / 2.0
-        h = np.sinc(u / resolution) * window
-        self.filt = []
-        for index in range(resolution):  # split into multiphase filters
-            filt = h[index::resolution]
-            filt = filt[::-1]
-            self.filt.append(filt)
-        lengths = map(len, self.filt)
-        assert set(lengths) == set([2*width])
-        assert len(self.filt) == resolution
-
-    def get(self, offset):
-        # offset = k + (j / self.resolution)
-        k = int(offset)
-        j = int((offset - k) * self.resolution)
-        coeffs = self.filt[j]
-        return coeffs, k - self.width
-
-class Sampler(object):
-    def __init__(self, src, interp):
-        self.src = iter(src)
-        self.freq = 1.0
-        self.interp = interp
-        coeffs, begin = self.interp.get(0)
-        self.offset = -begin  # should fill samples buffer
-        self.buff = np.zeros(len(coeffs))
-        self.index = 0
-
-    def __iter__(self):
-        return self
-
-    def correct(self, offset=0):
-        assert self.freq + offset > 0
-        self.offset += offset
-
-    def next(self):
-        res = self._sample()
-        self.offset += self.freq
-        return res
-
-    def _sample(self):
-        coeffs, begin = self.interp.get(self.offset)
-        end = begin + len(coeffs)
-        while True:
-            if self.index == end:
-                return np.dot(coeffs, self.buff)
-
-            self.buff[:-1] = self.buff[1:]
-            self.buff[-1] = self.src.next()  # throws StopIteration
-            self.index += 1
-
 def clip(x, lims):
     return min(max(x, lims[0]), lims[1])