diff --git a/lisainstrument/instrument.py b/lisainstrument/instrument.py
index 736bfc3dec9a27c7dea403e25457bfb0bb6b273c..07c267cdecdb37258de7266e7a04ba3e34b335e5 100644
--- a/lisainstrument/instrument.py
+++ b/lisainstrument/instrument.py
@@ -662,14 +662,14 @@ class Instrument:
         logger.debug("Propagating carrier fluctuations to distant MOSAs")
         carrier_fluctuations = \
             self.local_carrier_fluctuations \
-            + (self.central_freq + self.local_carrier_offsets) * self.distant_ttls / c
+            - (self.central_freq + self.local_carrier_offsets) * self.distant_ttls / c
         propagated_carrier_fluctuations = \
             (1 - self.d_pprs) * carrier_fluctuations.distant() \
             .transformed(lambda mosa, x: self.interpolate(x, -self.pprs[mosa]))
         self.distant_carrier_fluctuations = \
             propagated_carrier_fluctuations \
             - (self.central_freq + self.local_carrier_offsets) * self.gws \
-            + (self.central_freq + self.local_carrier_offsets) * self.local_ttls / c
+            - (self.central_freq + self.local_carrier_offsets) * self.local_ttls / c
 
         logger.debug("Propagating upper sideband offsets to distant MOSAs")
         self.distant_usb_offsets = \
@@ -680,14 +680,14 @@ class Instrument:
         logger.debug("Propagating upper sideband fluctuations to distant MOSAs")
         usb_fluctuations = \
             self.local_usb_fluctuations \
-            + (self.central_freq + self.local_usb_offsets) * self.distant_ttls / c
+            - (self.central_freq + self.local_usb_offsets) * self.distant_ttls / c
         propagated_usb_fluctuations = \
             (1 - self.d_pprs) * usb_fluctuations.distant() \
             .transformed(lambda mosa, x: self.interpolate(x, -self.pprs[mosa]))
         self.distant_usb_fluctuations = \
             propagated_usb_fluctuations \
             - (self.central_freq + self.local_usb_offsets) * self.gws \
-            + (self.central_freq + self.local_usb_offsets) * self.local_ttls / c
+            - (self.central_freq + self.local_usb_offsets) * self.local_ttls / c
 
         logger.debug("Propagating timer deviations to distant MOSAs")
         self.distant_timer_deviations = \