HD, OTA, Amp'd cable, and cable w/modem - voltage?

[SouthernSky]

Customer has a new Sony Wega Plasma. Wants to have Cox Cable for locals as well as cable internet, A Terk55 HDTV amplified OTA for local HD, and a Sony HD-300 Receiver for DirecTV.

I know when I use a 3-LNB dish, I also have to run the four wires to a Quad Diplexer when I need to connect amplified Cox Cable to the OTA port (DC blocked) during diplexing. Otherwise, the Cox cable modem backfeeds 15v and messes with the HD. Then I diplex at the TV like always. This I've done a number of times.

So now, how/where would you tie in a separately amplified Terk 55 HDTV OTA which is supposed to remain unobstructed to the OTA port of the Quad diplexer? Because of the separate amplified voltages to each device (the Terk and Cox), a splitter joining the two before they hit the OTA port of the Quad diplexer would seem to send the voltage into collision with each other inside the splitter. (And I think one is 15 AC and the other 17 DC).

Would some sort of splitter with both In ports having a voltage block seem logical? Or is there another way? Thanks in advance.

[oljim]

Why not do it the right way, get a real ant. not a trek and forget the diplexers

[SouthernSky]

Why not do it the right way, get a real ant. not a trek and forget the diplexers

The customer already bought everything online. I just have to install it.

[Mike500]

I've been working with telephones for over 40 years, including antique telephones. Telephones allow for both talking voltage and ringing voltage on the same two wire line. Talking voltage is -48 volts dc, while ringing voltage is 90 VAC. In the early days of telephony, the key was to find a means of delivering AC ringing voltage to the ringer, without having AC interfere with the DC talking circuit. The key was a .47uf 250 volt capacitor in the line. It allows AC to pass, but blocks DC.

This is why Thomas Edison, who founded General Electric, lost the "Battle of the Currents" with George Westinghouse and Nikolai Tesla. Transformers and capacitors do not work with DC.

In some way, you need to place a capacitor in the line going to the item requiring a DC supply.

If that doesn't work, place a diode in the line to the Terk 55. I don't know how well it would work with half wave DC or one phase AC.