diff --git a/calibratesdr/dabplus/dab.py b/calibratesdr/dabplus/dab.py
index 16965ef..f1479bf 100644
--- a/calibratesdr/dabplus/dab.py
+++ b/calibratesdr/dabplus/dab.py
@@ -5,7 +5,7 @@
 def get_ppm(data, samplerate = 2048000, show_graph = False, verbose=False):
     adc_offset = -127
 
-    data_slice = (adc_offset + data[0:: 2]) + 1j * (adc_offset + data[1:: 2])
+    data_slice = (data[0::2].astype(np.int16) + adc_offset) + 1j * (data[1::2].astype(np.int16) + adc_offset)
 
     signal = np.abs(data_slice)
 
diff --git a/calibratesdr/utils.py b/calibratesdr/utils.py
index bec6d79..4249e16 100644
--- a/calibratesdr/utils.py
+++ b/calibratesdr/utils.py
@@ -66,8 +66,8 @@ def get_fft(data, samplerate = 2048000):
     window = samplerate
 
     for slice in range(0, int(len(data) // (window * 2)) * window * 2, window * 2):
-        data_slice = (adc_offset + data[slice: slice + window * 2: 2]) +\
-                      1j * (adc_offset + data[slice + 1: slice + window * 2: 2])
+        data_slice = (adc_offset + data[slice: slice + window * 2: 2].astype(np.int16)) +\
+                      1j * (adc_offset + data[slice + 1: slice + window * 2: 2].astype(np.int16))
 
 
         norm_fft = (1.0 / window) * fftshift(fft(data_slice))