diff --git a/libraries/dsp/si/src/python/si.py b/libraries/dsp/si/src/python/si.py
index 27f77be077eb429d6107e7ec39941ea92b6a2725..3ba02f4000a5220082e1a5d551ff44c1b777a00b 100755
--- a/libraries/dsp/si/src/python/si.py
+++ b/libraries/dsp/si/src/python/si.py
@@ -36,6 +36,8 @@
 #     1st Nyquist zone: f =   0 - 100 MHz
 #     2nd Nyquist zone: f = 100 - 200 MHz
 #     3rd Nyquist zone: f = 200 - 300 MHz
+#   Spectral inversion flips the frequency bands (Nyquist zones), it does not
+#   shift frequencies.
 
 import argparse
 import textwrap