diff --git a/app/src/main/java/de/apps4ics/mountainnavigation/MyPhoneStateListener.java b/app/src/main/java/de/apps4ics/mountainnavigation/MyPhoneStateListener.java
index 0f7d088..39ee3d8 100644
--- a/app/src/main/java/de/apps4ics/mountainnavigation/MyPhoneStateListener.java
+++ b/app/src/main/java/de/apps4ics/mountainnavigation/MyPhoneStateListener.java
@@ -14,7 +14,8 @@
         if(signalStrength.isGsm()){
             int asu = signalStrength.getGsmSignalStrength();
             if(asu == 99){
-                MainActivity.setNetworkStrength(asu);
+                //MainActivity.setNetworkStrength(asu);
+                MainActivity.setNetworkStrength(-1); //unknown network strength
             } else {
                 MainActivity.setNetworkStrength(Math.round(asu/0.31f));
             }