I am assuming you have a new HD duo receiver (222k, 622, 722, 722k) or 612 solo receiver that doesn't have a coax connector for TV 1. You need to do 1 of 2 things to enable you to connect the old TV to your receiver. If your TV has an RCA port (yellow, white, and red cable) on the back, you can use that cable instead of the coax from the TV to the receiver.
If your TV doesn't have the RCA ports, you need to get an RF modulator to convert the signal from the receiver from RCA to coax.