Before revision: The RF/antenna output, if present on a converter box, is usually just a passthrough ("LOOP OUT" which does not provide the box's output signal, but only provides the raw antenna input signal to watch analog channels via the TV tuner if analog broadcasts have not ended yet or to connect another DVB-T2 capable device to the same antenna feed) because even older TVs usually have at least composite input; this removes a need for an RF modulator in a converter box
After revision: A RF/antenna output, if present on a converter box, is usually just a passthrough ("LOOP OUT" which does not provide the box's output signal, but only provides the raw antenna input signal to watch analog channels via a TV set's tuner if analog broadcasts have not ended yet or to connect another DVB-T2 capable device to the same antenna feed) because even older TVs usually have at least composite input; this removes a need for an RF modulator in a converter box