Beware of those large units for elimination of hum. Our station had a few for remote work. THEY READ DC CONTINUITY INPUT TO OUTPUT. They are actually a choke. Inside is a large toroid core wound with coax in to out. (I took one apart to see how it worked.)
Here is one on ebay for only $5.00. Probably see many of these for sale dirt cheap since analog video is not used in TV broadcasting anymore.
https://www.ebay.com/itm/14528665298...Bk9SR6ywl9byYg