Ferrites might work, but it's best to run whatever displays the interference on an EMI filter. The common mode chokes in most sets ain't enough. Ferrites don't work on TV coax well, if at all. A coaxial line isolator (See a good CATV supplier, or check eBay..) might work - but only with
RF interference - they were used with Satellite systems back in the 90s/2000s
Best options:
1) Get yourself an AC line conditioner ($$$$) I use a Sola, but mostly for line regulation (132V at my outlets.....yes, too high, right off the tranny outside.) It filters out
everything but >400msec surges. Pricey items - got mine surplus for pennies.
2) Build your own EMI filter ($) Use an IEC EMI input filter, and a wall outlet output. I made one back in 2002ish for a Navy need. Be sure to carry the ground to a common point.
IEC filter:
https://www.google.com/search?q=emi+...w=1280&bih=834
3) Buy a TDK or Murata (may be sold under KEC as well) EMI Filter - used ($), new ($$). We used the TDKs on computers - the dot matrix machines we had (22" platen) would generate all sorts of noise on one phase of the line. The TDKs are only rated for 6 or 8 amps, plenty for a TV. The Muratas are larger and harder to find anymore. Schaffner may make some standalones like the TDKs.
The X10 Home control system also offered one - it used to be available at RadioShack, good for 5A, and $20 or so. Check eBay.
Other tips - use quality coax from Belden/Alpha or Channel Master. Most of the discount store stuff is cheapo 40% coverage - you want >90% coverage, which is braid AND shield foil.
Try plugging the TV into an outlet that is off a different leg than the other items. Tough to figure out if you don't have the means to trace the circuit from the panel to the outlet.