diff --git a/src/preambles.py b/src/preambles.py
index fb15ff0..d8b5f9c 100644
--- a/src/preambles.py
+++ b/src/preambles.py
@@ -19,14 +19,12 @@ def generate_preamble_symbols(n_symbols_to_send):
     else:
         raise ValueError('This preamble type does not exist yet... Hehehe')
 
-    if params.MAPPING == "qam" and not params.NORMALIZE_MAPPING and params.PREAMBLE_TYPE == "barker":
-        # TODO: improve that
-        if params.M == 16:
-            read_write.write_preamble_symbols(preamble_symbols * 3)
-        elif params.M == 4:
-            read_write.write_preamble_symbols(preamble_symbols)
-    else:
-        raise ValueError('TODO: automate the scaling of the barker sequence')
+    if params.MAPPING == "qam" and not params.NORMALIZE_MAPPING:
+        number_of_points_on_side = np.sqrt(params.M)/2.0
+        test_value = np.log2(params.M)/2.0
+        if test_value != int(test_value):
+            raise ValueError('Not a valid Qam value')
+        read_write.write_preamble_symbols(preamble_symbols * (2.0*number_of_points_on_side - 1))
 
     return None