There could be a number of causes, but basically the vent and charger are generating radio frequency interference that is getting into the TV.
You didn't say if you were using a dish, antenna or DVD/bluray. Try playing a DVD or Bluray and see if the interference goes away. If it does, you need to look at the antenna/dish/satellite box and all cables very closely.
Easiest things first... can you move your antenna or satellite dish farther away?
Didn't help? Check all wiring to the vent, charger and TV/box/dish/antenna, every inch of it. Repair or replace any wiring that is less than perfect, including any signal cables between the TV/box/dish/antenna. Unscrew them and look closely at the ends, any that the center pin is dull or dark should be replaced, that center pin should be a bright, shiny copper color. Pay particular attention to any outdoor parts (dish, antenna, cables, connectors). Replace anything that looks like a corroded connection, pinched cable or any other kind of damage. Remember that the connector on the dish, and the connector on the side of your trailer have to be good too. Check the wiring to the vent and charger too, I've seen many loose crimp connectors causing all kinds of problems.
Get an outlet tester and verify that your 120 volt shore power is properly grounded and not reverse polarity, check it at the outlet the TV is plugged into. A battery that is very low on charge or at the end of it's useful life can cause some strange issues too, especially since you say running the charger is one of the problems. If the TV is a 12 volt RV TV, not 120 volts I would definitely start looking at the battery and it's connections.
If you are happy that all the wiring and connections are perfect, see if you can start substituting parts. Borrow from home or another RVer. Try a different TV, even if you hook it up temporarily, try a different satellite box or dish or antenna. Try different cables, even if they looked good.
Still not good? Make notes of everything you tried and what results you got and head for somebody who does trailer wiring. There's a good chance you are looking for a bad ground connection.
And if all else fails, radio amateurs (hams) usually have experience and knowledge at removing interference (what we call RFI). Look up the ham club in your area, (https://www.facebook.com/W5DRZ
) chances are they will be happy to give you a hand. You may need some filters or toroidal chokes installed (that's probably the worst case scenario) but they aren't too expensive.
I know it's a lot, but check things one step at a time and make notes on what you find. Hope this helps!