[Tom Nugler]

Have to agree that the noise is likely caused by a digital device close to the radio or antenna.
The diagnostic scan tools we use in the shop to check the vehicles computers will blank out the normal radio signals in most cars. Newer radios and antenna systems are designed to help mitigate RFI, but I doubt CB technology has advanced much since the "80s.
Try moving the antenna to another location if possible. I assume the radio is near the dash and all the "Telemetrics". To check if the interference is coming from that area, try moving it away (out the door for example) to see if the noise changes. If not it's being picked up by the antenna. If it is, it's picking it up from near the area where it's mounted.
Hope this helps, but I haven't had to troubleshoot this type of problem in years.
Good luck, Tom.