diff --git a/supersdr.py b/supersdr.py
index f779d69..6426444 100755
--- a/supersdr.py
+++ b/supersdr.py
@@ -702,7 +702,8 @@ def draw_lines(surface, wf_height, radio_mode, mouse):
             cat_radio.get_mode()
             radio_mode = cat_radio.radio_mode
         else:
-            del cat_radio
+            radio_mode = "USB"
+            cat_radio = None
     except:
         cat_radio = None
         radio_mode = "USB"