Without using an old analog receiver, can the polarity be switched as needed? It is the 5volt, three wire black for ground, red for 5 volts, white for pulse Chaparral feed horn with a Drake 2766 lnb.
There are "Automatic Polarity Controllers" available. About $40. I've seen them on Ebay but not at the moment. They can be self powered or run off a power supply.