Let the GUI support GSM 1800 and 1900 frequency bands.
diff --git a/apps/airprobe_rtlsdr.grc b/apps/airprobe_rtlsdr.grc
index 64e20a5..bbec4c0 100644
--- a/apps/airprobe_rtlsdr.grc
+++ b/apps/airprobe_rtlsdr.grc
@@ -513,7 +513,7 @@
     </param>
     <param>
       <key>stop</key>
-      <value>960e6</value>
+      <value>1990e6</value>
     </param>
     <param>
       <key>step</key>