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Discussion Starter · #1 ·
Is it a good idea to modulate TV signals onto 1 common coax from different locations? There is no off-air on this coax (or in the neighborhood).


The 4DTV and DISH receivers are being distributed thru the house on channels 15 and 25. I'd like to add a 2nd DISH receiver in the bedroom and modulate its signal with another Channelplus, and use yet another Channelplus modulator in the office to modulate the VGA output for a scrolling program guide.


And - anybody know of any good FM stereo modulators for cable distribution? Kind of like a car cassette adapter, but with a wall-wart and coax out?
 

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You can do this, but it's not recommended. The whole reason you want to send all the video to a central headend is to ensure power levels are the same to each jack in the house. If you modulate in the bedroom, and you output at 15 db, your TV there gets that signal at 15 db, but the TV at the opposite end of the house might see a signal 10 db down because of the coax and splitter losses. If you have a small house and not too much in the way of losses, you might be able to get away with it, but it's a pain to deal with.


On the FM side, if there is no other signals coming in, why not run your in house video modulators at 200 Mhz or above, and then use a couple of low pass filters between the FM antenna and your distribution system. No reason not to put the whole FM spectrum on the plant. If you do this though, YOU MUST MAKE SURE NO SIGNAL FROM THE HOUSE GETS TO THE ANTENNA! Else you will earn the ire of many. I would use multiple low pass filters to make sure you get about 50 to 60 db of isolation between your modulators and the antenna, so it doesn't raidate those signals outside. You also may need an amp to boost the signal properly so it'll be OK in all the rooms. The amp would also block all the signals from the house from getting there. Depends on what you are trying to pick up.


Thanks,

Mike
 

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Discussion Starter · #3 ·
I guess I should "homerun" the VandA from the bedroom to the living room, where the all the existing modulators are, and then modulate it and add it to the coax there.


As regards the FM, I must have garbled what I am doing.


I live in a canyon - no off-air FM available. Thus, no antenna.


I am seeking a way to modulate stereo audio for distribution on cable to several FM radios down the coax.


I would rather not run audio cables across the house ... but I have never found an FM modulator that would do this.


I've goofed around with those cheap FM modulators for car use but they are battery-powered, weak, and prone to hiss. Plus they have no way to connect to the house cable.


Thanks for your expertise. Any suggestions???
 

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Ok, sorry about that. I know what you are talking about now. What you are looking for is a commercial style FM modulator that is designed to feed signls into a CATV plant. I only know of one off hand that does this, and it's expensive. Check out:

http://www.21best.com/21_best/electr...l#anchor196875


You might find some other products that will do this by searching the web.


Do you have a lot of FM radios wired to the CATV system? It seems a lot easier to distribute the audio by using a conventional stereo CATV modulator, but without a video signal, or the output of a simple screen generator. TV's could then be used instead of radios, or using TV band capable radios would work too.


If you have CAT5 wiring around, you could also use some audio baluns and use it to push the audio signal around instead of seperate audio cables.


But I understand what you are trying to do - seems reasonable, but sometimes it's hard to find the box you need.


Thanks,

Mike
 
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