diff --git a/FM.cpp b/FM.cpp
index 2bed736..fa5fd53 100644
--- a/FM.cpp
+++ b/FM.cpp
@@ -36,7 +36,7 @@ m_kerchunkTimer(),
 m_ackMinTimer(),
 m_ackDelayTimer(),
 m_hangTimer(),
-m_filterStage1(  724,   1448,   724, 32768, -37895, 21352),
+m_filterStage1(  724,   1448,   724, 32768, -37895, 21352),//3rd order Cheby Filter 300 to 2700Hz, 0.2dB passband ripple
 m_filterStage2(32768,      0,-32768, 32768, -50339, 19052),
 m_filterStage3(32768, -65536, 32768, 32768, -64075, 31460),
 m_blanking(),