RFI can be hard to figure out, and throwing money
in the form of "maybe" new equipment
isn't something I'd usually suggest. However, not all coax cable is the same, and most if not all of the marine
coax on the market does not have a 100% shield in the "shield" layer. Combine that with the fact that as coax ages, the properties of it change, and if it hangs unsupported in the mast
(as almost all of it does) the section in the mast
pulls itself thinner, like taffy on a hot day, degrading itself a bit more every year.
So, if your cable is ten years old? It might make sense to replace it with a premium grade new cable, properly supported and with a 100% shield layer, and see if that also cures the RFI problem at the same time.
Or, borrow, buy, or build an inexpensive "emergency" antenna
, and see if the VHF
still picks up the RFI when using that. (Quicker & simpler than expanding the project
list with a new antenna