Sign error

Author: fronzbot

tests/test_spectrum.py

@@ -88,7 +88,7 @@ def test_sndr_sfdr_outputs(self):
                 "power": 9,
                 "rms": 3,
                 "dBHz": round(-11.5297 - full_scale, 1),
-                "NSD": round(-11.5297 - full_scale - 48.1648, 1),
+                "NSD": round(-11.5297 - full_scale + 48.1648, 1),
             },
             "sndr": {
                 "dBc": 10.0,