diff --git a/simulations/airshower_beacon_simulation/bb_measure_true_phase.py b/simulations/airshower_beacon_simulation/bb_measure_true_phase.py
index f95d172..3fae81a 100755
--- a/simulations/airshower_beacon_simulation/bb_measure_true_phase.py
+++ b/simulations/airshower_beacon_simulation/bb_measure_true_phase.py
@@ -9,30 +9,6 @@ import numpy as np
 import aa_generate_beacon as beacon
 import lib
 
-def antenna_true_phases(tx, antennas, freq_name, c_light=3e8):
-    """
-    Determine true phases from the antenna phases.
-
-    This removes the geometrical phase from the antenna phase.
-    """
-    if not hasattr(antennas, '__len__'):
-        single_ant = True
-        antennas = [antennas]
-
-    true_phases = np.empty( (len(antennas)) )
-    for i, ant in enumerate(antennas):
-        beacon_info = ant.beacon_info[freq_name]
-        measured_phase = ant.beacon_info[freq_name]['phase']
-        f_beacon = ant.beacon_info[freq_name]['freq']
-
-        geom_time = lib.geometry_time(tx, ant, c_light=c_light)
-        geom_phase = geom_time * 2*np.pi*f_beacon
-
-        true_phases[i] =  lib.phase_mod(lib.phase_mod(measured_phase) - lib.phase_mod(geom_phase) )
-
-    return true_phases
-
-
 if __name__ == "__main__":
     from os import path
     import sys
@@ -71,18 +47,18 @@ if __name__ == "__main__":
     N_beacon_freqs = len(antennas[0].beacon_info)
 
     for freq_name in antennas[0].beacon_info.keys():
-        true_phases = antenna_true_phases(tx, antennas, freq_name, c_light=c_light)
+        true_phases = lib.antenna_true_phase_diff(tx, antennas, freq_name, c_light=c_light)
 
         # Remove the phase from one antenna
         # this is a free parameter
         # (only required for absolute timing)
         if remove_absolute_phase_offset_first_antenna or remove_absolute_phase_offset_minimum:
             if remove_absolute_phase_offset_first_antenna: # just take the first phase
-                minimum_phase = -1*true_phases[0]
+                minimum_phase = true_phases[0]
             else: # take the minimum
-                minimum_phase = -1*np.min(true_phases, axis=-1)
+                minimum_phase = np.min(true_phases, axis=-1)
 
-            true_phases += minimum_phase
+            true_phases -= minimum_phase
             true_phases = lib.phase_mod(true_phases)
 
         # Save to antennas in file
@@ -99,7 +75,7 @@ if __name__ == "__main__":
         if show_plots or fig_dir:
             fig, ax = plt.subplots()
             spatial_unit=None
-            fig.suptitle('True phases\nf_beacon= {:2.0f}MHz'.format(f_beacon*1e3))
+            fig.suptitle('Clock phases\nf_beacon= {:2.0f}MHz'.format(f_beacon*1e3))
 
             antenna_locs = list(zip(*[(ant.x, ant.y) for ant in antennas]))
             ax.set_xlabel('x' if spatial_unit is None else 'x [{}]'.format(spatial_unit))
@@ -108,7 +84,7 @@ if __name__ == "__main__":
             scatter_kwargs['cmap'] = 'inferno'
             scatter_kwargs['vmin'] = -np.pi
             scatter_kwargs['vmax'] = +np.pi
-            color_label='$\\varphi$'
+            color_label='$\\varphi(\\sigma_t)$ [rad]'
 
             sc = ax.scatter(*antenna_locs, c=true_phases, **scatter_kwargs)
             fig.colorbar(sc, ax=ax, label=color_label)
diff --git a/simulations/airshower_beacon_simulation/lib/lib.py b/simulations/airshower_beacon_simulation/lib/lib.py
index 70a67ce..e6ed9d4 100644
--- a/simulations/airshower_beacon_simulation/lib/lib.py
+++ b/simulations/airshower_beacon_simulation/lib/lib.py
@@ -53,6 +53,32 @@ def beacon_from(tx, rx, f, t=0, t0=0, c_light=3e8, radiate_rsq=True, amplitude=1
 
     return sine_beacon(f, t, t0=t0, amplitude=amplitude,**kwargs)
 
+def antenna_true_phase_diff(tx, antennas, freq_name, c_light=3e8):
+    """
+    Determine true phases from the antenna phases.
+
+    This removes the geometrical phase from the antenna phase.
+    """
+    if not hasattr(antennas, '__len__'):
+        single_ant = True
+        antennas = [antennas]
+
+    true_phases = np.empty( (len(antennas)) )
+    for i, ant in enumerate(antennas):
+        beacon_info = ant.beacon_info[freq_name]
+        measured_phase = beacon_info['phase']
+        f_beacon = beacon_info['freq']
+
+        geom_time = geometry_time(tx, ant, c_light=c_light)
+        geom_phase = geom_time * 2*np.pi*f_beacon
+
+        print(ant.name, measured_phase, geom_phase, phase_mod(geom_phase))
+
+        true_phases[i] = phase_mod(phase_mod(measured_phase) - phase_mod(geom_phase) )
+
+    return true_phases
+
+
 """ Fourier """
 def ft_corr_vectors(freqs, time):
     """