1 files changed, 7 insertions, 2 deletions
diff --git a/calctenna.py b/calctenna.py
index c4670c1..79d6ce1 100755
--- a/calctenna.py
+++ b/calctenna.py
@@ -12,10 +12,11 @@ def run_argparse():
     argparser.add_argument(
         '-f',
         '--frequency',
+        required=True,
         metavar='frequency',
-        help='desired frequency in Hz',
+        help='desired frequency in Hz (e.g. 144800000 or 433e6, ...',
         nargs='?',
-        default='100e6'
+        #default='100e6'
     )
     argparser.add_argument(
         '-V',
@@ -32,6 +33,10 @@ def run_argparse():
     )
     args = argparser.parse_args()
 
+    if not args.frequency:
+        argparser.print_usage()
+        exit()
+
     return args
 
 def calc(args):