Most multiswitched pass voltage to the OTA antenna port for powering an amplified antenna, including providing a source of power to the antenna amplifier. Both Winegard and Channel Master (now a subsity of Andrew) provide amplifiers, without power supplies, to use on dbs multiswitches. A lot of companies that sell multiswitches include DC voltage blocks.
I'd power up the switch and measure the voltage at the OTA port.