diff --git a/tnc/modem.py b/tnc/modem.py
index ecf52e15..e6b00791 100644
--- a/tnc/modem.py
+++ b/tnc/modem.py
@@ -792,6 +792,8 @@ class RF:
                         # we need to disable this if in testmode as its causing problems with FIFO it seems
                         if not TESTMODE:
                             static.IS_CODEC2_TRAFFIC = True
+                            # set channel busy state to True
+                            static.CHANNEL_BUSY = True
 
                         self.log.debug(
                             "[MDM] [demod_audio] modem state", mode=mode_name, rx_status=rx_status,