Problems with small signals through BNC connectors?
While there are many possible sources of noise in your setup, you've found it's associated with &quot;twisting of the cable&quot; and have suggested it's related to the connector pin rotating.
That's possible, but you should also consider &quot;triboelectric noise&quot; as well. This is a well-known source of noise in medical instrumentation cables carrying low-level signals (EEG, EKG, etc). It's basically caused by static electricity being generated as the conductors rub against the dielectric insulation.
You need to do a differential diagnosis. If the noise is worst when you &quot;do the twist&quot; near the connector, your hypothesis is probably right. But if there's noise when you clamp the cable a few inches from the connector and &quot;do the twist&quot; on the free portion, then it's probably triboelectric. Look into higher quality low-noise cables designed for medical instrumentation. Good luck!