Electricity issue? TV blacking out when the heater is on.

I thought my tv was just dying but I've since figured out that it only blacks out if the space heater tower is on. Could it have something to do with the current being low? I have a multimeter and checked the AC volts and it's right on 120v It really does seem connected to that. The second the heater goes on sometimes, but usually soon after, the tv goes black but the the sound continues. I couldn't figure out why it didn't do it in the afternoon (but lately with the A/C on it has (!) but then would do it later at night. Then in a bit the picture will come on again. If it was the heat it would be going out during the day when it's warmer, right?

If that is the case what would be causing it? I'm on 50A at the post.