diff --git a/simulations/airshower_beacon_simulation/ca_period_from_shower.py b/simulations/airshower_beacon_simulation/ca_period_from_shower.py
index 458ad9b..ee03958 100755
--- a/simulations/airshower_beacon_simulation/ca_period_from_shower.py
+++ b/simulations/airshower_beacon_simulation/ca_period_from_shower.py
@@ -206,7 +206,7 @@ if __name__ == "__main__":
         clock_phase_time = clock_phase/(2*np.pi*f_beacon)
 
         ev.antennas[i].orig_t = ev.antennas[i].t
-        ev.antennas[i].t -= clock_phase_time
+        ev.antennas[i].t += clock_phase_time
 
         if False: # remove beacon from trace
             meas_phase = ant.beacon_info[freq_name]['phase']