diff --git a/gqrx-panadapter.py b/gqrx-panadapter.py
index d058906..042ad38 100755
--- a/gqrx-panadapter.py
+++ b/gqrx-panadapter.py
@@ -101,7 +101,7 @@ def calc_lnb_lo(freq, ifreq, isusb=True):
         if DEBUG:
             print('USB IF: ' + str(ifreq + usb_if_offset))
         #return - freq - (ifreq - usb_if_offset)
-        return freq + usb_if_offset - ifreq
+        return -freq + usb_if_offset - ifreq
     else:
         if DEBUG:
             print('LSB IF: ' + str(ifreq + lsb_if_offset))