[2] 811 dishnet receiver

Question

HAVE THESE TWO RECEIVERS 1 DOWNSTAIRS AND 1 UPSTAIRS WHEN YOU GO TO CHANGE CHANNELS ,IT CHANGES BOTH SETS. I TOOK ANTENNA OFF 1 SET ,BUT DOES;T WORK ON THAT SET WITHOUT ANTENNA HOW CAN I STOP IT FROM WORKING BOTH SETS AT THE SAME TIME THANK YOU D.S.