The DB4e / CPA-19 preamp and HD7084P / CPA-19 preamp , are 2 separate systems and Will Not be connected together on to one coax. The 2 separate systems will have separate coax all the way to the location of the tv , where the 2 separate systems will be connected to a remote control A/B antenna switch and the output of the A/B antenna switch is connected to the tv. The remote control antenna switch is a Radio Shack # 15-1968.
http://www.radioshack.com