diff --git a/amodem/audio.py b/amodem/audio.py
index dabe275..3b70ff8 100644
--- a/amodem/audio.py
+++ b/amodem/audio.py
@@ -26,7 +26,7 @@ class Interface:
 
     def call(self, name, *args, **kwargs):
         assert self.lib is not None
-        func_name = 'Pa_{0}'.format(name)
+        func_name = f'Pa_{name}'
         if self.debug:
             log.debug('API: %s%s', name, args)
         func = getattr(self.lib, func_name)
@@ -81,7 +81,7 @@ class Stream:
         assert read != write  # don't support full duplex
 
         direction = 'Input' if read else 'Output'
-        api_name = 'GetDefault{0}Device'.format(direction)
+        api_name = f'GetDefault{direction}Device'
         index = interface.call(api_name, restype=ctypes.c_int)
         self.params = Stream.Parameters(
             device=index,               # choose default device
diff --git a/amodem/calib.py b/amodem/calib.py
index 4b9f50b..59f7f45 100644
--- a/amodem/calib.py
+++ b/amodem/calib.py
@@ -18,7 +18,7 @@ def volume_controller(cmd):
     def controller(level):
         assert 0 < level <= 1
         percent = 100 * level
-        args = '{0} {1:.0f}%'.format(cmd, percent)
+        args = f'{cmd} {percent:.0f}%'
         log.debug('Setting volume to %7.3f%% -> "%s"', percent, args)
         subprocess.check_call(args=args, shell=True)
     return controller if cmd else (lambda level: None)
@@ -73,7 +73,7 @@ def detector(config, src, frame_length=200):
         if success:
             msg = 'good signal'
         else:
-            msg = 'too {0} signal'.format(errors[flags.index(False)])
+            msg = f'too {errors[flags.index(False)]} signal'
 
         yield dict(
             freq=freq, rms=rms, peak=peak, coherency=coherency,
@@ -135,7 +135,7 @@ def recv(config, src, verbose=False, volume_cmd=None, dump_audio=None):
     log.info('verbose: %s', verbose)
     if verbose:
         fields = ['total', 'rms', 'coherency', 'peak']
-        fmt += ', '.join('{0}={{{0}:.4f}}'.format(f) for f in fields)
+        fmt += ', '.join(f'{f}={{{f}:.4f}}' for f in fields)
 
     for state in recv_iter(config, src, volume_cmd, dump_audio):
         log.info(fmt.format(**state))
diff --git a/amodem/detect.py b/amodem/detect.py
index 7677e90..be47285 100644
--- a/amodem/detect.py
+++ b/amodem/detect.py
@@ -113,5 +113,5 @@ class Detector:
 
         freq_err = a / (self.Tsym * self.freq)
         log.info('Frequency error: %.3f ppm', freq_err * 1e6)
-        self.plt.title('Frequency drift: {0:.3f} ppm'.format(freq_err * 1e6))
+        self.plt.title(f'Frequency drift: {freq_err * 1e6:.3f} ppm')
         return amplitude, freq_err
diff --git a/amodem/recv.py b/amodem/recv.py
index 84f21f0..c4f6c66 100644
--- a/amodem/recv.py
+++ b/amodem/recv.py
@@ -45,7 +45,7 @@ class Receiver:
         self.plt.plot(equalizer.prefix)
         errors = (bits != equalizer.prefix)
         if any(errors):
-            msg = 'Incorrect prefix: {0} errors'.format(sum(errors))
+            msg = f'Incorrect prefix: {sum(errors)} errors'
             raise ValueError(msg)
         log.debug('Prefix OK')
 
@@ -94,7 +94,7 @@ class Receiver:
         for (i, freq), snr in zip(enumerate(self.frequencies), SNRs):
             log.debug('%5.1f kHz: SNR = %5.2f dB', freq / 1e3, snr)
             self._constellation(symbols[:, i], train_symbols[:, i],
-                                '$F_c = {0} Hz$'.format(freq), index=i)
+                                f'$F_c = {freq} Hz$', index=i)
         assert error_rate == 0, error_rate
         log.debug('Training verified')
 
@@ -188,7 +188,7 @@ class Receiver:
             symbol_list = np.array(self.stats['symbol_list'])
             for i, freq in enumerate(self.frequencies):
                 self._constellation(symbol_list[i], self.modem.symbols,
-                                    '$F_c = {0} Hz$'.format(freq), index=i)
+                                    f'$F_c = {freq} Hz$', index=i)
         self.plt.show()
 
     def _constellation(self, y, symbols, title, index=None):