A true UPS will do it, but most UPS uhits are actually IPS (inturruptable) and will drop out for a tiny fraction of a second.. Now DirecTV does not seem to be bothered but DISH receivers are.
A better option is an inverter to power the electronics... You install a good True Sine Inverter like my Prosine (no longer made so it's LIKE, not the same) and disable the charger side, Cut off the 30 amp breaker feeding the inverter and . It switches to inverter.. My Progressive Dynamics 9180 keeps the batteries upo for most uses. Microwave will take 'em down.
NOTE: if all you run it the TF and other Entainerment stuff, a much smaller inverter will suffice (and a smaller converter) Say a Samulex 300