Can I do composite over coax? How? - AVS Forum
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post #1 of 6 Old 03-30-2008, 11:22 AM - Thread Starter
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Hi all. I have an existing video distribution system in my home using a SD Tivo to drive multiple TVs using the old-style RF Out connection feeding a powered splitter/amp over RG-6. I'm considering a new D* DVR system, and the new boxes do not have an RF Out connection. They do have composite, so I'm wondering if I can use an RCA-to-F connector adapter to go from the new box's composite output, over the existing RG-6 coax thru another F conn-to-RCA adapter to my TVs. Basically, using the coax to distribute composite video signal.

Anyone tried this? Seems like it ought to work, unless there are some impedance matching issues.

I'm also curious if my splitters/amplifiers will work as well.

There's always the "hook it up and check for smoke approach", but I thought someone might have tried this before. ( a smart man learns from his mistakes, but a wise man learns from the mistakes of others :-) )

Thanks!

I'm finding that I'm smarter than I thought, but dumber than I need to be.
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post #2 of 6 Old 03-31-2008, 02:15 AM
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You would only have video and no audio however with that method, unless you used an RF modulator.
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post #3 of 6 Old 03-31-2008, 03:52 AM - Thread Starter
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Quote:
Originally Posted by Joxer View Post

You would only have video and no audio however with that method, unless you used an RF modulator.

That would work just fine for me. I have a Russound whole house audio system that I use for audio. It also repeats IR commands from each zone (room) to the main Tivo box.

So, the coax splitters/amp would work as well?

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post #4 of 6 Old 04-01-2008, 02:00 AM
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No coax RF splitters/amplifiers wouldn't work with a baseband composite video signal.
Something specific for 75ohm composite video would be needed, video distribution amplifiers.
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post #5 of 6 Old 04-04-2008, 05:24 PM
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Quote:
Originally Posted by rtart View Post

Hi all. I have an existing video distribution system in my home using a SD Tivo to drive multiple TVs using the old-style RF Out connection feeding a powered splitter/amp over RG-6. I'm considering a new D* DVR system, and the new boxes do not have an RF Out connection.

I am guessing that everything you are doing is Standard Definition. Personally, I'd never use RF out.

Quote:


They do have composite, so I'm wondering if I can use an RCA-to-F connector adapter to go from the new box's composite output, over the existing RG-6 coax thru another F conn-to-RCA adapter to my TVs. Basically, using the coax to distribute composite video signal.

No. If you want to convert video & audio outputs into RF, you need a modulator. The output of the modulator (typically channel 3 or 4) could then feed into your existing system. This approach will result in about the lowest quality video you could get.

Quote:


Anyone tried this? Seems like it ought to work, unless there are some impedance matching issues. I'm also curious if my splitters/amplifiers will work as well.

RF splitters and amplifiers are typically designed to pass somewhere around 50 MHz (just below channel 2) to 900 MHz (well above channel 69). NTSC video is typically DC to 10 MHz or DC to 4.2 MHz from an off-the-air broadcast.

It sounds like you want to take video (and audio) from one place and "distribute" it to many places around your house. Last time I checked, Radio Shack sold a "distribution amplifier" for this purpose. Connect your DVR output into the amp, and it provides 4 or so sets of outputs. Run cables to each location. However, long cable runs can be problematic.

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post #6 of 6 Old 04-05-2008, 07:52 AM - Thread Starter
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Thanks CA Guy,

My system includes a Russound whole house audio system that allows me to use the Tivo audio as one source, and also use the Russound's IR repeating capability to control the Tivo box from any room. I actually started out years ago when I installed this system with a D* receiver used only for satellite music as one audio source, along with tuners and CD changers. To make it easier to select the correct audio channel on the D* receiver, I plugged a TV into the RF output of the D* box. Worked fine, so I plugged it into the existing cable TV coax system already in place throughout the house. Although the PQ is not great, it works fine for the five or six 27" CRT TVs in several rooms in the house. The four 50" and 58" plasmas and the CRT PJ in the theater all have their own HDTivos.

The logic behind using composite over coax comes from my plans to upgrade all receivers to the MPEG-4 DVRs soon. I plan to also replace the SD tivo that feeds my Russound system with a new D* DVR with the non-Tivo GUI, so all DVRs use the same interface. (WAF.) The new D* SD DVRs do not have a RF output, so I'll need to use composite video (or something else) instead. My idea was to use the existing coax throughout the house for composite distribution, instead of pulling new wiring.

It appears that I can use a video ditribution amplifier to accomplish this. I've found a few on eBay that apear to meet my needs. I tried to find a local source for the video dist amps, so I could return them easily if they don't work for me. I've tried CC, BB and Fry's, but no luck. Rat Shack is next on my list, then fleabay.

Thanks to all for your help. I'll return to this post with results so others may learn from my experiences.

I'm finding that I'm smarter than I thought, but dumber than I need to be.
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