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622 and cable on TV2

Discussion in 'ViP612/622/722/722K DVR Support Forum' started by MSG, Mar 9, 2006.

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  1. Mar 9, 2006 #1 of 13
    MSG

    MSG Cool Member

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    Dec 15, 2004
    How to combine 622 and cable on TV2? Did anybody do it?
     
  2. Mar 9, 2006 #2 of 13
    lifterguy

    lifterguy Legend

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    I've never done with the 622, but I have combined an off air antenna with a Dish Network receiver output to send it to a second tv, using a simple multiplexer. The multiplexer combines the channel 3 output from the dish reciever with the OTA antenna output. I think this might work in a similar way with cable and the 622, but I'm not entirely sure. Here are the questions I can't answer right now:
    -First - Can you set the 622 TV2 output to Channel 3? (I think it defaults to a UHF channel, and I can't remember in what I've read if it will allow you to use Channel 3.)
    -Second - Assuming you can use channel three, my proposed solution would only allow you to see the modulated output for either TV2 or TV1 (the 622 modulates both outputs, but on two different channels - a basic multiplexer can only combine one channel with your OTA or Cable output)
    -Third - Since most cable systems have something on channel 3, I'm not sure if this would work, since the channel on cable 3 might interfere with the multiplexed channel 3.
    If you want to give it a try, you can buy a multiplexer for about $20. This is one source:
    http://www.dishstore.net/index.php?cPath=50
    There may be more sophisticated multiplexers out there, but I'm not aware of where to get one.
     
  3. Mar 9, 2006 #3 of 13
    MSG

    MSG Cool Member

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    Unfortunately channel 3 is not going to work. 622 is only aloud to use 23-69 as an AIR channels or 73-125 as a CABLE channels. I tired to use regular cable splitter, and cable channels looks fine, but modular TV2 signal from 622 works very snowy.
     
  4. Mar 9, 2006 #4 of 13
    DoyleS

    DoyleS Icon

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    You will likely have to do a little analysis to figure out just where the problem is. First thing is to ensure you have a good signal coming from the 622 modulator. Hook a TV directly to the modulator output with no other cabling connected and make sure the signal looks good on the TV when tuned to the Cable channel that you have your 622 set for. If that is good then connect your modulated output to your internal cable system and disconnect your incoming Cable TV signal. You should just have the modulated signal on you house distribution cable. Check with a remote TV and see if the picture is ok. If the picture is now snowy then you likely have a signal loss problem due to a poor splitter or bad cable in your system. If the picture is good then you can connect the Cable TV signal back to the internal distribution cable and check the signal. Note that you need to be spaced 2 channels away from any other channel to prevent interference. If you cable TV channels go up to 80 or so, I like to set my modulator up around 120 and then delete the in between channels so that the tv skips directly from say channel 79 to channel 120.

    Snowy picture normally means that you have signal loss someplace due to using a low quality splitter, too many splitters in series or possibly a poor or faulty cable run.

    ..Doyle
     
  5. Mar 9, 2006 #5 of 13
    MSG

    MSG Cool Member

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    Thanks, Doyle. I tried to hook a TV directly to the modulator output with no other cabling connected and the signal looks good on the TV2. So, it’s not a splitter or cable. Then I tried to do a combination and used different channels up to 79 without success. I will try channel 120 or so tonight.
     
  6. Mar 9, 2006 #6 of 13
    DoyleS

    DoyleS Icon

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    With your splitter, be sure it is good to 1000 MHz. It should be stamped or written on the splitter. With your cable system, what range are the cable channels?
    Are you saying you were able to send the signal from the modulator onto the coax in your home to a remote TV and receive that with no snow? I should probably distinguish between house Coax and Cable where Cable refers to the signal coming in from the Cable TV system whereas Coax refers to the internal coax cable that runs around your house and goes through 1 or two splitters. I am unsure whether you have been able to successfully send a modulator signal around that house coax with the Cable TV signal disconnected.

    ..Doyle
     
  7. Mar 9, 2006 #7 of 13
    MSG

    MSG Cool Member

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    Yes I have been able to successfully send a modulator signal around that house coax with the Cable TV signal disconnected.
     
  8. Mar 9, 2006 #8 of 13
    DoyleS

    DoyleS Icon

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    OK, so it really sounds like it might be a channel interference problem. Basically you will need to look for a free channel that also has no signal on the channel directly above and below it. Bottom line is that a lot of these modulators are not of the highest quality and so any signal overlap can cause problems with the channel you are trying to receive.

    ..Doyle
     
  9. MSG

    MSG Cool Member

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    Dec 15, 2004
    Right. It is a channel interference problem. I am looking for the sort of filter to clear some bandwidth for 622 modulator. Looks like Comcast sending noise on the channels they don’t use or something.
     
  10. James Long

    James Long Ready for Uplink! Staff Member Super Moderator DBSTalk Club

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    Noise: Probably high speed internet or digital TV channels.
     
  11. mitch672

    mitch672 AllStar

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    Feb 28, 2006
    What you need is either a notch filer, or bandpass filter to elliminate the noise/interference comming from the cable system.

    Channel Plus makes several different models, and even Leviton made a nice one that filtered channels 75 through 80 (so you could insert modulated channels 75, 77, 79 for example), Home Depot had these for $30 originally, last time I checked they where closing them out at $4.00

    Here is the link to one of the ones from Channel Plus:

    http://www.channelplus.com/product_detail.php?productId=66

    This one rejects cable channels 64-70, for example...
    http://www.channelplus.com/product_detail.php?productId=76

    Also, using a high quality splitter/combiner helps:
    http://www.channelplus.com/product_detail.php?productId=27

    Mitch
     
  12. DoyleS

    DoyleS Icon

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    Looks like we are zeroing in on the problem. You will likely need a low pass filter. Basically it is a filter that passes all of the cable channels below a specific channel. Depending on the highest channels you use and whether or not you are using a Cable Modem for Broadband access, You will likely need a filter that passes everything below channel 116. (that is why I tend to use channels like 120-125). Here is a link to Smarthomes website. They have a number of these filters for various needs along with explanation on how to use them. They also have notch filters that clear a section of the band such as channels 64-70. This may or may not cause problems for you.
    http://www.smarthome.com/prodindex.asp?catID=695&p=2&s=6
    Smarthome typically is not the lowest price place but once you know what you need, you can shop it online. The filter is inserted right where your cable TV signal enters the house so that all of the coax in the house only has the channels on it that you want. You do your combine on a filtered Cable line.


    ..Doyle

    Oops....looks like Mitch and I were typing answers at the same time. All good info.
     
  13. MSG

    MSG Cool Member

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    Dec 15, 2004
    Thanks. I will experiment over the weekend now and will post the results.
     
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