diff --git a/simulations/airshower_beacon_simulation/lib/tests/test_calculated_phase_measurement.py b/simulations/airshower_beacon_simulation/lib/tests/test_calculated_phase_measurement.py
index f36619e..83cbb38 100755
--- a/simulations/airshower_beacon_simulation/lib/tests/test_calculated_phase_measurement.py
+++ b/simulations/airshower_beacon_simulation/lib/tests/test_calculated_phase_measurement.py
@@ -18,6 +18,7 @@ dt = 1 # ns
 frequency = 45e-3 # GHz
 N = 5e2
 c_light = lib.c_light
+t_clock = 3/4 * 1/frequency
 
 t = np.arange(0, 10*int(1e3), dt, dtype=float)
 rng = np.random.default_rng(seed)
@@ -48,16 +49,21 @@ for i in range(int(N)):
         blank_low, blank_high = 2*int(1e3), 4*int(1e3)
         beacon[blank_low:blank_high] = 0
 
+    # Introduce clock errors
+    t += t_clock
     measured = lib.find_beacon_in_traces([beacon], t, frequency, frequency_fit=False)
+    t -= t_clock
 
     calculated_phase = lib.remove_antenna_geometry_phase(tx, rx, frequency, measured[1][0], c_light=c_light)
 
     phase_res[i] = lib.phase_mod(calculated_phase - phase)
 
+# Make the figure
 fig, ax = plt.subplots()
 ax.set_title("Measured phase at Antenna - geometrical phase")
 ax.set_xlabel("$\\varphi_{meas} - \\varphi_{true}$ [rad]")
 ax.set_ylabel("#")
-ax.hist(phase_res, bins='sqrt')
+ax.hist(phase_res, bins='sqrt', density=False)
+ax.axvline( -1*lib.phase_mod(t_clock*frequency*2*np.pi), color='red', lw=5, alpha=0.8, label='true t_clock')
+ax.legend()
 plt.show()
-