diff --git a/amodem-cli b/amodem-cli
index 4fbe8ea..9751712 100755
--- a/amodem-cli
+++ b/amodem-cli
@@ -19,11 +19,8 @@ import logging
 
 log = logging.getLogger('__name__')
 
+from amodem import recv, send, audio, calib
 from amodem.config import bitrates
-from amodem import recv
-from amodem import send
-from amodem import audio
-from amodem import calib
 
 null = open('/dev/null', 'wb')
 
@@ -76,12 +73,6 @@ def main():
         '-c', '--calibrate', default=False, action='store_true')
     sender.add_argument(
         '-w', '--wave', default=False, action='store_true')
-    sender.add_argument(
-        '--silence-start', type=float, default=1.0,
-        help='seconds of silence before transmission starts')
-    sender.add_argument(
-        '--silence-stop', type=float, default=1.0,
-        help='seconds of silence after transmission stops')
 
     sender.set_defaults(
         main=run_send,
@@ -101,9 +92,6 @@ def main():
         '-c', '--calibrate', default=False, action='store_true')
     receiver.add_argument(
         '-w', '--wave', default=False, action='store_true')
-    receiver.add_argument(
-        '--skip', type=int, default=320,
-        help='skip initial N samples, due to spurious spikes')
     receiver.add_argument(
         '--plot', action='store_true', default=False,
         help='plot results using pylab module')
@@ -152,10 +140,10 @@ def join_process(process):
     sys.exit(exitcode)
 
 
-def run_modem(args, func):
-    args.input = args.input_type(args.input)
-    args.output = args.output_type(args.output)
-    func(args)
+def run_modem(args, main_func, **kwargs):
+    src = args.input_type(args.input)
+    dst = args.output_type(args.output)
+    main_func(args.config, src, dst, **kwargs)
 
 
 def run_send(args):
@@ -173,7 +161,7 @@ def run_recv(args):
     elif args.wave:
         join_process(audio.record(Fs=config.Fs).launch(fname=args.output))
     else:
-        run_modem(args, recv.main)
+        run_modem(args, recv.main, plt=args.plot)
 
 
 if __name__ == '__main__':
diff --git a/amodem/config.py b/amodem/config.py
index 8213269..03f246e 100644
--- a/amodem/config.py
+++ b/amodem/config.py
@@ -8,6 +8,13 @@ class Configuration(object):
     Npoints = 64
     F0 = 1e3
 
+    # sender config
+    silence_start = 1.0
+    silence_stop = 1.0
+
+    # receiver config
+    skip_start = 0.1
+
     def __init__(self, **kwargs):
         self.__dict__.update(**kwargs)
 
diff --git a/amodem/recv.py b/amodem/recv.py
index ccb2181..857824a 100644
--- a/amodem/recv.py
+++ b/amodem/recv.py
@@ -209,24 +209,24 @@ class Receiver(object):
         self.plt.title(title)
 
 
-def main(args):
-    config = args.config
-    reader = stream.Reader(args.input, data_type=common.loads)
+def main(config, src, dst, plt=None):
+    reader = stream.Reader(src, data_type=common.loads)
     signal = itertools.chain.from_iterable(reader)
 
-    skipped = common.take(signal, args.skip)
-    log.debug('Skipping %.3f seconds', len(skipped) / float(config.baud))
+    to_skip = int(config.skip_start * config.Fs)
+    log.debug('Skipping %.3f seconds', config.skip_start)
+    common.take(signal, to_skip)
 
     reader.check = common.check_saturation
 
     detector = detect.Detector(config=config)
-    receiver = Receiver(config=config, plt=args.plot)
+    receiver = Receiver(config=config, plt=plt)
     success = False
     try:
         log.info('Waiting for carrier tone: %.1f kHz', config.Fc / 1e3)
         signal, amplitude = detector.run(signal)
         receiver.start(signal, gain=1.0/amplitude)
-        receiver.run(args.output)
+        receiver.run(dst)
         success = True
     except Exception:
         log.exception('Decoding failed')
diff --git a/amodem/send.py b/amodem/send.py
index 865236d..9b935db 100644
--- a/amodem/send.py
+++ b/amodem/send.py
@@ -52,19 +52,19 @@ class Sender(object):
                 log.debug('Sent %8.1f kB', total_bits / 8e3)
 
 
-def main(args):
-    sender = Sender(args.output, config=args.config)
-    Fs = args.config.Fs
+def main(config, src, dst):
+    sender = Sender(dst, config=config)
+    Fs = config.Fs
 
     # pre-padding audio with silence
-    sender.write(np.zeros(int(Fs * args.silence_start)))
+    sender.write(np.zeros(int(Fs * config.silence_start)))
 
     sender.start()
 
     training_duration = sender.offset
     log.info('Sending %.3f seconds of training audio', training_duration / Fs)
 
-    reader = stream.Reader(args.input, bufsize=(64 << 10), eof=True)
+    reader = stream.Reader(src, bufsize=(64 << 10), eof=True)
     data = itertools.chain.from_iterable(reader)
     bits = framing.encode(data)
     log.info('Starting modulation')
@@ -75,4 +75,4 @@ def main(args):
              reader.total / 1e3, data_duration / Fs)
 
     # post-padding audio with silence
-    sender.write(np.zeros(int(Fs * args.silence_stop)))
+    sender.write(np.zeros(int(Fs * config.silence_stop)))
diff --git a/tests/test_transfer.py b/tests/test_transfer.py
index 15eee9e..8d16f63 100644
--- a/tests/test_transfer.py
+++ b/tests/test_transfer.py
@@ -29,8 +29,7 @@ class Args(object):
 def run(size, chan=None, df=0, success=True):
     tx_data = os.urandom(size)
     tx_audio = BytesIO()
-    send.main(Args(config=config, silence_start=1, silence_stop=1,
-              input=BytesIO(tx_data), output=tx_audio))
+    send.main(config=config, src=BytesIO(tx_data), dst=tx_audio)
 
     data = tx_audio.getvalue()
     data = common.loads(data)
@@ -45,8 +44,7 @@ def run(size, chan=None, df=0, success=True):
     rx_audio = BytesIO(data)
 
     rx_data = BytesIO()
-    result = recv.main(Args(config=config,
-                            skip=0, input=rx_audio, output=rx_data))
+    result = recv.main(config=config, src=rx_audio, dst=rx_data)
     rx_data = rx_data.getvalue()
 
     assert result == success