While running CAT control on the Yaesu FT-891 I noticed that a persistent clicking noise was not very loud but generally super annoying. Without making any changes to the USB cable, I found that I could control the severity of the noise by altering the baud rate in OmniRig. It stops whenever I close OmniRig and stop using CAT.
The FT-891 features three baud rates in menu 05-06 CAT Rate I chose to put that at the maximum number. On my rig it’s 38,400bps. This has to match the baud rate in OmniRig. Once the settings matched both on the radio and on the computer, the noise was much shorter but, unfortunately, it was still present. So what I was hearing is the query command from the computer to the radio and possibly the radio’s response as well. At least by choosing a higher baud rate the noise became shorter and slightly less annoying.
I’ve already tried clamping a ferrite bead on the USB cable with no effect. I suspect perhaps my cable is unshielded and the signal is getting picked up on the coax shielding, so I have ordered a proper shielded USB cable and I will update the article with the result. As is stands now, the noise is more bearable, but still present in my headphones.