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Diplexing OTA with Long Cable Runs to the ViP622...

Discussion in 'ViP612/622/722/722K DVR Support Forum' started by kkrull, Apr 20, 2006.

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  1. kkrull

    kkrull New Member

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    Apr 20, 2006
    My RG6 cable runs from the roof 80 feet down and unions to another cable that runs to my main room 80 feet of cable away. Maybe it is even longer as I didn't wire the building myself.

    The 622 sees the dish antenna just fine over this setup, but when I try to diplex an outdoor HDTV OTA antenna in to the Dish Network stream and back out I get zero signal for OTA.

    Any suggestions? When testing from the roof I can get 90db signal strength, even with a couple of diplexers in and out of some short cable lengths. If I haul the antenna down next to the 622, I get strong signal, but the walls are so thick that the tall buildings create a very different directional signal path for each station. Not to mention that the antenna is too big for the room.

    I have tried a 10db amplifier by the tv (which I was glad didn't mess up the Dish Network) but it doesn't improve the OTA either. I thought about trying a 25db amp, or moving the amp to the junction halfway between the dish and the receiver or even on the roof.

    Is there an easier way to debug this? What are the possible causes of signal loss? This isn't a specific to the 622. None of my devices can see the diplexed OTA signal.
     
  2. madbrain

    madbrain Legend

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    Dec 10, 2004
    Is it possible that you need to change/repoint your OTA antenna ?
    Did you ever have your antenna connected directly to the TV, perhaps before you had Dish ?

    I have a very similar setup similar to yours. Signal comes from my OTA antenna 50ft down to the DPP44 in my crawl space. Then it is diplexed with the 1st output of the DPP44. Then there is about another 40ft of wiring to the power inserter and diplexer in the living room. I get great signal from both Dish and OTA - 33 OTA digital channels in the SF bay area.
     
  3. dougmcbride

    dougmcbride AllStar

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    Apr 17, 2005
    Not sure if this will help or not, but I had a similar experience a few weeks ago. Hooked up an OTA antenna to the satellite cable run via diplexers and got 0 signal. In hindsight I should have been suspicious at the number 0 since OTA is not that hard to get in the area where the antenna was installed. Chased a wide variety of ghosts and even hooked the antenna up directly via a borrowed long run of coax with almost 100 signal stength. Swapped diplexers, etc., etc.

    Finally gave up and was going to go back and install a separate coax run for the OTA antenna - a major PITA but what can you do? A day or so later it came to me in a flash that there was a dual coax grounding block in the loop that I had not checked and sure enough, the coax lines had gotten swapped and swaping them back did the trick (I was sending the OTA signal to another room in the house, not the one I thought it was going to :lol: ).

    In any case, it sounds like you should be seeing some level of signal but not 0 if you have good diplexers and the coax is the one you think it is. Food for thought...

    Good luck,

    Doug
     
  4. DoyleS

    DoyleS Icon

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    Oct 21, 2002
    El Dorado...
    First of all, any amplifier you use would need to be added up near the antenna. Otherwise you are only amplifying noise. By placing the amp near the TV you will destroy your signal to noise ratio. It sounds like you have a total of 160 feet of RG6 cable. With that length, you will have somewhere between 10 to 15 db of loss just in the cable. Any Diplexers or other connections will also add to the loss. Depending on which channels you are trying to receive, the loss could be higher. The higher the UHF channel number, the higher its frequency and greater will be the loss. It sounds like you will need all 10 db from that amp placed up at the antenna. Are you sure the amp is a UHF amplifier?

    ..Doyle
     
  5. oljim

    oljim Godfather

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    Aug 6, 2002
    Dump the diplexers, run a new cable from ant to 622
     
  6. Jim5506

    Jim5506 Hall Of Fame

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    Jun 7, 2004
    AMEN!!
     
  7. kkrull

    kkrull New Member

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    Apr 20, 2006
    Cable is in a full sealed conduit so no new cable runs.

    Good point. I don't have power on the roof, but I can move the amplifier to the first junction inside. Can I amplify the Dish signal too, or do I need to diplex the Dish signal around the amp? The amp is a basic $30 RCA coax amp but I would buy whatever I needed.

    Not sure how to check this. Wouldn't the grounding block prevent the Dish signal too? My Dish signal is ok.
     
  8. DoyleS

    DoyleS Icon

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    Oct 21, 2002
    El Dorado...
    If your sat signal is good now then diplex around the amp. There are a couple types of Amplifiers. Some amps are made to be distribution amps. They do not have great signal to noise characteristics. Other amps are made to be mounted on the antenna and they receive their power through the coax. This may or may not be easy for you to handle depending on your situation. Which model RCA amp do you have? We can look up the specs on it. You can check this page from Stark electronics.
    http://www.starkelectronic.com/allamps.htm
    They sell VHF/UHf antenna amps and typically they have 20db gain on the UHF frequencies. They refer to them as Preamps as they are really meant to be as close to the antenna as possible. A 10 DB amp sounds more like a distribution amp to me and often you will not see any difference in signal with a distribution amp. They are made more for taking a strong signal and boosting it even higher before you go through a bunch of splitters. Signal to noise is really the key spec not just gain.

    ..Doyle
     
  9. dougmcbride

    dougmcbride AllStar

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    Apr 17, 2005
    Sorry - my point was that I was trying to get the OTA signal off the other coax line that was going to a location other than where I thought it was, which was why I was getting "0" as opposed to a degraded signal if it was a long cable run or insertion loss from the diplexor. Didn't seem obvious at the time that the two coax lines could have been swapped but they were. One way to check is disconnect the coax at the source and see if you get no satellite signal at the unit where you have the diplexor.

    I agree a dedicated coax run is ideal, but not always practical.

    Doug
     
  10. kkrull

    kkrull New Member

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    Apr 20, 2006
    There is a lot of information on that page. What do you recommend?

    If I could really power a decent S/N preamp off the coax I think that would be the best bet if it didn't mess up the Dish Network signal. Otherwise I will have to add two more diplexers to the system (total of four) to get into and out of the amp in the distribution room because I only have one run from the roof and one run to the Dish receiver.

    I have one run of coax running dish pro plus signal from a dish 1000 three satellite setup on the roof. All I am trying to pickup on the OTA is HDTV.

    Another option is a large indoor antenna that is thin enough to fit under the couch or behind the AV cabinet, but I assume that since an expensive outdoor antenna in the room was having trouble with the thick walls and tall surrounding buildings, that most indoor antennas wouldn't cut it.
     
  11. DoyleS

    DoyleS Icon

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    Oct 21, 2002
    El Dorado...
    I don't think the indoor antenna is going to work based on the description of your location.

    I think your best bet is to call the guys at Stark antenna. They have a preamp that is designed to run off of the power that runs your SAT LNBs.

    "The Spartan 3 preamplifiers range has been enhanced with the addition of models OO65DSB and 0265DSB. These units are identical to the familar OO64DSB and 0264DSB except they have been designed for optimum performance with a supply voltage of 12-22 VDC as supplied by most satellite receivers "

    You can describe your specific situation to them and they can make sure that the preamp is compatible with the Dish 1000 signal/DPP equipment. If your OTA signal are only UHF then get the UHF only amp. You will need to know whether it is coax in or 300 ohm twinlead. You may have a small transformer on the antenna that converts from balanced 300 ohm to 75 ohm coax. That could be replaced with a preamp that takes 300 ohm twinlead in. That would eliminate another source of loss in your signal. You really want to make the lowest number of transformers and diplexers in your signal path. Keep us informed on how this goes, I am sure this thread will be useful to others as well.

    ..Doyle
     
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