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SD Signal Loss From Long Cable Run

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

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  1. lbeck

    lbeck AllStar

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    Jun 27, 2006
    I have >100ft run of cable from my 622 to TV2. Of course, I know that I can't get HD on TV2, but I'm having problems getting full-quality SD. I also had a problem with just TV antenna losses in the system and years ago installed an amplified distribution system. I quickly found out that it doesn't work for the 622 modulator. In fact, I had to disconnect the amplifier and join cables with a barrel connector to get TV2 to accept the signal at all. Then, I did notice some degradation from the picture quality that I had from a temporary direct hookup of about 40 ft of cable going up the stairwell. The longer cable run is of course because of going through walls, ceilings, etc. to keep the cable hidden. I installed the distribution system myself in an existing structure and didn't have the luxury of choosing the shortest possible route. I plan to split the signal further for a couple of other "TV2"s.

    Are there signal amplifiers for the modulator signal used by the 622? What are my other options? I don't have a reasonable way to shorten the distance.
     
  2. Manke

    Manke Mentor

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    Dec 27, 2005

    I have well over 200 feet of cable with splitters feeding 5 sets from the 622 using my old cable channel amplifier from Radio Shack. The only issue I have had with the 622 is low audio level off the modulated signal. The cabeling is what was installed in the home when built in the eighties so nothing unique (RG59).
     
  3. lbeck

    lbeck AllStar

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    Jun 27, 2006
    Maybe that's the difference - Your amp is for cable and mine is for antenna.

    I was thinking that something different was needed for the modulated signal from the 622. If not, I'll just get a cable signal amplifier. I'm presuming that the amp does a reasonable job of improving PQ and doesnt introduce any artifacts other than the sound problem you mention. The picture quality even with the long cable run is only a tad grainy but I do notice a degradation from the shorter cable run and I'd like to get the best quality possible within my limitations.

    I've never had cable. I switched from antenna to satellite about 20 years ago and never looked back. We've kept the antenna on the roof just because it's free and never has storm outages. I'm now thinking that I'll switch the distribution system to the 622 modulator.
     
  4. lbeck

    lbeck AllStar

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    Jun 27, 2006
    Okay, I'm looking at the RS Catalog #: 15-2506.

    Frequency Range = 54-1000 MHz
    Gain = 8dB

    For about $50. I'm assuming that this is adequate, or is something other recommended.
     
  5. LtMunst

    LtMunst Hall Of Fame

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  6. Mark Lamutt

    Mark Lamutt Your Neighborhood Liasion

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    lbeck - you may want to try a different channel for tv2 as well. On my setup, I see vast signal quality differences depending on what channel I select to modulate my TV2 output on. Some channels look great, others look terrible.
     
  7. lbeck

    lbeck AllStar

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    Jun 27, 2006
    Thanks to each of you for your responses. I'll probably go for the $50/4 output/8db model rather than the $30/1 output/10db model. The situation that i'm facing is a 27 inch TV2 in the LR that is watched even more than the 55" PTV (TV1) in den downstairs. But there also is a 19" in the BR that is almost never used and a 13" in the kitchen that my wife watches a lot. But she doesn't care about PQ. The thing that would change my consideration for you techies is whether db is a linear or logrithmic scale. I'm assuming that 10 is only 20% greater than 8, and having the extra hookup capacity may be more important than the extra 20% signal. Decisions decisions.

    The thing that really confuses me is that the RS amp looks disturbingly similar to the antenna distribution amp I already have and which seemed to block the modulator signal. Also, the RS info for the amp I'm going to buy says that it can be used to amplify cable OR antenna signals.

    The reason for my temporary hookup (the shorter cable run down the open stairwell) was that I couldn't get any of the TV2s to process the 622 signal. I ran the shorter cable just to confirm that my LR TV would work as a TV2 with my 622. When I confirmed that it would, I suspected the amp and replaced it with a barrel connector and the distribution system worked, but the longer length of cable showed some dorpoff in PQ.

    My assumption, now in question, was that antenna amps won't work for the 622 signal. Apparently many users are using cable TV amps that do work, so I'm thinking that maybe my antenna amp is specific to a narrow operating frequency (it is about 30 years old) or that it had some sort of short or other problem that did not show up when I was using it solely for antenna.

    I'll also try different channels. I hadn't heard that was a consideration in PQ and I don't believe that it is covered in the 622 manual.
     
  8. CABill

    CABill Hall Of Fame

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    The reason for changing the modulated channels is to avoid existing signals. You can use www.Antennaweb.org to find channels you need to avoid - the digital OTA channels may not appear on your TV2s, but have signal that would interfere with the 622 output. When you disconnected from the amp and used barrel connectors, any chance that you also eliminated the Antenna source from the coax? If you have boosted the Ant signal, the 622 could be fighting more channels than appear in the Antennaweb.org list.
     
  9. LtMunst

    LtMunst Hall Of Fame

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    Actually, it is logarithmic with +3db equaling twice the power.
     
  10. Mark Lamutt

    Mark Lamutt Your Neighborhood Liasion

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    lbeck - try different channels. An amp is an amp. The only reason it could "block" the signal is if its defective. Now, if you choose to modulate on a channel that already has something broadcast on it, that would effectively block the modulated output from the 622. That's why its so important to choose a channel that is clear.
     
  11. Manke

    Manke Mentor

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    Dec 27, 2005
    The one I am using is the 15-2505:

    http://www.radioshack.com/product/i...ifier&kw=cable+tv+amplifier&parentPage=search

    Also when I used a high number channel off the 622 I recieved a poor picture so choose the lowest clear channel you can find. For best results make sure that both adjacent channels to the one you are using are clear too and if you are sending both Tv1 and Tv2 signals out keep them a couple of channels off each other.
     
  12. LEADTECH DNSC

    LEADTECH DNSC Cool Member

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    Jul 25, 2006
    it can go well over 200feet an still have clear picture, the problems i have seen in cust homes with this is:
    Bad cable or rg59
    Bad barrel somewhere
    A Splitter somewhere on the line in the wall or in clear view uselly seems to be the problem though witch a amp will fix
     
  13. Larry Kenney

    Larry Kenney Legend

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    Aug 19, 2005
    Just a quick note on channel selection. Use the LOWEST channel you can. You get less loss at the lower frequencies.

    When I installed my 622 TV line of about 75 feet, I found that channel 23 was crystal clear but channel 60 was a bit snowy. I'm using 23 and 35 successfully.

    Another bit of info that might help some of you... if you have trouble with your remote working reliably due to distance from the receiver or RF interference in the area, and you have no amps in line, use a splitter at each end of your TV2 coax. At the receiver end connect one output of the splitter to the RF output of the receiver and the other to the remote antenna connector. At the TV end, connect one output to your TV and connect your remote antenna whip to the other. Your coax will carry the remotes signal via the coax back to your receiver. It solved my problem! (I think my problem is due to all the RF floating around here. I'm only 3/4 of a mile from Sutro Tower which has 10 analog and 11 digital TV transmitters, four FM stations, and lots of other stuff sending out signals.)

    Larry
    SF
     
  14. lbeck

    lbeck AllStar

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    Jun 27, 2006
    How close can you be to an adjacent channel or to zero? I receive channels 4-5-11-17-22-28-40-50. I believe that 2 is the lowest VHF channel. Also, there is a station broadcasting on 2 and it is about 100 miles away, but I do get a very snowy picture if I tune there manually (it isn't "saved"). Is it okay to use 2?
     
  15. CABill

    CABill Hall Of Fame

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    You can't use VHF channels. The UHF choices only go down to 21. You may get better results if there isn't another channel ajacent to the one you pick, but try 21 eventhough you said you had a 22. I can't tell where in NC you are, but that sounds like the ANALOG channels in Raleigh-Durham. There are other channels you'd want to avoid. Channel 27 is what is used for digital channel 28.1. Enter your zipcode at http://www.antennaweb.org/aw/Address.aspx and note the channels used in the Frequency Assignment column for the digital stations wherever you are. You don't want to pick something that is used. The PBS from Chappel Hill on 4.1 actualy uses channel 59, and can interfere with the default channel 60.
     
  16. lbeck

    lbeck AllStar

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    Jun 27, 2006
    Thanks, I'm currently using 64 but will switch to 21. How will I know if I made a bad choice? Ghosting? Bleed through of the other channel? Snow (noisy picture)? Or just a bad picture like a weak signal from the long cable length.

    BTW, you're right about my location. My locals are the Raleigh/Durham channels.

    Thanks
     
  17. SaltiDawg

    SaltiDawg Active Member

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    Aug 30, 2004
    The 622 is selectable to output either OTA Ch21- 69 or Cable 73 - 125.

    Is yout 622 selected for OTA on the TV2 A?V out?
     
  18. LEADTECH DNSC

    LEADTECH DNSC Cool Member

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    Jul 25, 2006
    Best Bet For The Best Picture Is Press Menu-then 6-1-5, Thats Brings You Into The Modulador Screen. Then Change It To Cable An It Will Automatic Go To Channel 73, Then Change Your Tv Settings From Antenna To Cable An Put It On 73, Going To The Lowest Channel Does Not Help Cause It Is An Antenna Channel. Witch Picks Up Alot Of Junk Freq,
     
  19. James Long

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

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    I hope you realize that "Cable Channel 73" and "OTA Channel 21" are basically the same frequency. It's just a case of changing the name.

    AIR - 21 - 513.25 - UHF
    CATV KKK - 73 - 517.25
    http://www.arrl.org/tis/info/catv-ch.html
     
  20. CABill

    CABill Hall Of Fame

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    It is a bad choice if YOU aren't happy with it. I had assumed that you used a splitter/combiner to also carry the Off Air signals from an antenna to the distant rooms. If not, there is quite a bit less interaction with the Home Dist channel and existing OTA (but a length of coax does act like an antenna - just not a great one).

    You could see all the issues you mention, depending on lots of factors. Using RG59 instead of RG6 wouldn't be one of those factors, but each barrel/splitter/... will take a toll on signal quality. It isn't necessary to try every channel to see which is "best" (unless you want to). You should try 2 or 3 and quit if you get satisfactory results. As Larry said several posts ago, the lower the channel (frequency), the less loss you see from coax length, number of connections, ... That needs to be balanced against signals already present. You might have better luck with 24/25 than 21 since it SEEMS like nothing is used on 23 thru 26. Cable 73 would interact more with OTA 22 you have present than using OTA 21 for distribution.
     
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