Using diplexers the other direction

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Original poster
Mar 5, 2004
When the installer was here to put in our 3-LNB Terk dish, I asked him about watching the output from one receiver on a TV in another room. He said I could use diplexers to send the output of the receiver (after being split to the TV and a diplexer) back through the cable, then another diplexer sends the RF signal to the coax that goes to the remote TV. This doesn't seem to work. I bought Terk diplexers and they came with DC filters, althoughh they didn't explain why they're needed. I put them on the cable/antenna/whatever jack of both diplexers.

Any thoughts or ideas on why it doesn't work, if it should work, or how to get it to work?
I really do not understand what you are trying to accomplish, much less, why.

Are you trying to run a satellite feed in one direction and the RF in the opposite direction? I was under the assumption that the diplexers were directional, in that there were two sources on one end and two destination on the other, which shared the single media for a while.
Yes, send the sat signal to a receiver, then split the output and send it back through the same cable, and diplex it out to another TV.

So they're unidirectional, huh? Crap. My DirecTV installation guy said he's done this before. I wonder if I need special diplexers?
Yes, you can use diplexers to back feed your video signal through your satellite cable. The reason you can do so, is that your satellite signal is on a different frequency band than your RF (video) signal. You will insert a diplexer into the line, with your wire coming from LNBF connected to the SAT connection on the diplexer. You will send the ANT connection to your second television. At the receiver itself, you will insert another diplexer into the line, and connect the SAT cable to your receivers satellite antenna input. Assuming you are using RF connection (channel 3 or 4) for your primary tv, you need to use a 2 way splitter to split the cable coming out of the receiver, with one cable to your tv, and the other to the ANT leg of your diplexer. You should now be able to get a picture on both tv's.

Best of luck.

That sounds like the way I have it wired. But since explaining wiring diagrams in text can be misinterpretted, here's an image of the way I have it. Does that look right to you?
One other thing: Each diplexer came with an inline DC blocker and the instructions said to put them on the ANT jack on each diplexer, so that's what I did. What purpose do these serve? I don't know anything about RF signals in wires, but I assume they're AC?
Yes, that diagram is correct. If you are positive you have it wired that way and it doesn't work, your diplexers may be bad.

The DC blockers direct the 13-18v signals to the LNBF. There is no reason for the voltage to go to the antenna. Especially if your antenna is amplified, in which you have a seperate power supply that would go to the antenna.

The diplexers we use have the dc blocker built into the diplexer.

Have you verified the functionality of the RF splitter you are using? I.E. it is providing good output from both ports? What's the frequency range of the splitter?

Whats the approximate physical distance of the cable between the output of your receiver and the tv in the second room. It's possible the signal strength has dropped enough that your television is unable to lock on the channel you are broadcasting through the diplexer. That splitter cuts the power in half, so you could try it once just sending the signal directly through the diplexer rather than splitting it first. See if that helps. If it does, then you know it's a signal power problem. A signal amplifier before the signal is split can improve that.

To eliminate the diplexer as the problem you could take the diplexers out of the loop, disconnecing the receiver and the dish and run the coax directly off the back of the receiver to the remote TV. If it works then, one or both diplexers may be an issue.
Groovy, I got it working. It ended up being a bad short patch cable I had between the splitter and diplexer. Thanks for mentioning the debugging process. That should've been the first thing I tried, being a software engineer, amateur electrical geek, and former car stereo installer. :)

Thanks again for the all the help, y'all. Now if I could just figure out why this Sony universal remote we got only sends signals for the volume buttons when it's set up to control the RCA DirecTV box. Stupid thing!
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