diff --git a/application/libraries/Frequency.php b/application/libraries/Frequency.php
index 0c21b3430..553ecd719 100644
--- a/application/libraries/Frequency.php
+++ b/application/libraries/Frequency.php
@@ -1,7 +1,7 @@
 <?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
 class Frequency {
 
-  const modes = array('SSB','FM','AM','CW','DSTAR','F4M','DMR','DIGITALVOICE',
+  const modes = array('SSB','FM','AM','CW','DSTAR','C4FM','DMR','DIGITALVOICE',
                       'PSK31','PSK63','RTTY','JT65','JT65B','JT6C','JT9-1', 
                       'JT9','FT4','FT8','JS8','FSK441','JTMS','ISCAT','MSK144','JTMSK', 
                       'QRA64','PKT','SSTV','HELL','HELL80','MFSK16', 'JT6M', 'ROS');