Congratulations!
That was an easy one, and a good thing to try.
A dozen ferrite cores slipped over the coax, in lieu of the "RF Choke balun" you made out of coax, probably also would have worked and sometimes is easier, if you happen to have the ferrites laying around.
The advantage of the ferrite cores, as opposed to the coil of coax, is you can get ones that just clamp right over the existing coax, so no real "work" needs to be done -- and, you can slide them up and down the coax line, to see what location is most effective at eliminating the RFI.
Good job, though!