I fought this for years with another radio- and later after much testing and trying found it can be caused by some network cables getting RF on them
Use type 31 or 43 mix ferrites on the network cable both ends-
Also I found and this varies from station to station- sometimes using regular cat5e with unshielded connector (as in no metal clip on connector) helps and sometimes cat6 with the grounded metal shield-
Also connecting the radio to your computer using a flat wide ground strap can help-
Use good cabling for mic connectors StarQuad cabling is a very good choice- en.wikipedia.org/wiki/Star_quad_cable
Another source can be your PC as well use good cables for any wired cabling you have on your PC- ground your PC (loosen a case screw or one on the power supply and bond there) and a good RFI/EMI surge strip can help as well.
If your using a switch or router that is housed in a metal box, ground it - If plastic good luck- move it in another location as it could be picking up the RF as well
It can be a never ending battle it seems at times. good luck