diff --git a/map65.py b/map65.py
index 51302d7b5..8322f1673 100644
--- a/map65.py
+++ b/map65.py
@@ -1089,6 +1089,9 @@ def update():
     tx4.configure(bg='white')
     tx5.configure(bg='white')
     tx6.configure(bg='white')
+    if tx6.get()[:3] != 'CQ ' and len(tx6.get())>13:
+        tx6.configure(bg='pink')
+
     if tx6.get()[:1]=='#':
         try:
             txsnrdb=float(tx6.get()[1:])