CATV Tiling - Some Channels, One TV Only - AVS Forum
Cable, Digital Cable - Non-HDTV > CATV Tiling - Some Channels, One TV Only
jasnn's Avatar jasnn 05:20 AM 11-23-2008
I'm having problems debugging the last of my Comcast CATV signal problems, and I was hoping someone might be able to give me some advice.

The 2 main TVs here are HD LCDs, with Tivo Series 3 PVRs connected to them, in two separate locations. Most of the HD channels we regularly watch, (local, and movie channels), we receive fine on both TV/Tivos. However, the main TV/Tivo is noticeably lower on signal levels, (using the crude signal meters in the Tivos as a point of reference), across the board. This lower signal level creates problems when watching a few HD channels, which include the local Fox affiliate, and channels like Animal Planet and AMCHD, ONLY on the main TV/Tivo. When watched, the reception results in some severe tiling, sprinkled with complete signal dropouts. Again, the secondary TV/Tivo, which has a stronger signal, shows no problems with all channels.

The main TV/Tivo, is a longer run of cable, about 100 feet, as opposed to 50 feet for the secondary location. All of these runs are brand new quad shielded RG6. The main run I've actually run twice, with no noticeable difference in the signal level. This main run does go under the house, as opposed to the secondary run which goes through the attic. The CATV distribution is in the attic and consists of the CATV input running about 30 feet to a Viewsonics 2 way splitter, which fed at first, 2 Viewsonics VSMA-608C-10R 8 way drop amps. I installed all 12 of my runs, and then terminated the 4 remaining ports. This did improve the main location signal levels, but the problem channels still showed some tiling and dropouts. I then swapped out one of the Viewsonics VSMA-608C-10R 8 way drop amps, for a VSMA-604C-10R 4 way drop amp, for just the long distance runs. Again the signal level improved slightly, but not enough to be watchable.

There are no splitters anywhere else. My cable modem signal values are Downstream SNR 33.403dB, Power 6.3dBmV, and Upstream 22.4 dBmV now, coming off of a port on the VSMA-604C-10R. As part of this CATV re-cabling/upgrade, I also installed a TII 212 Coaxial Lightning Surge Protector at the entry point to our home which I grounded. I also noticed that when I grounded the two Viewsonics drop amps, the picture on the problem location TV/Tivo seemed to improve a bit more, but again the dropouts make watching the channel impossible. So the system is grounded at the drop amps, and the main entry point, only.

I have run the main TV/Tivo cable twice, but I ran it along the same route under the house. It's also a dual run, and both cables exhibit the same behavior. At this point I'm thinking that I may have run the cable under or over something that is causing these slight signal variations. So I've ordered a 1000' roll of high quality quad shielded RG6, and I'm going to rerun the cable using a different path under the house. Otherwise I'm not sure what I should be looking at. My questions would be;

1) Is it better to amp the incoming signal higher, and send it to a splitter? Or is my setup of splitter first to 2 drop amps ok? (BTW, is it ok to go about 30 feet with the CATV system input before amping it?)

2) Does a CATV system need to be grounded at every device, amp, splitter, where there's a ground screw? Or only once?

3) Do you need to do something special for runs of about 100 feet, like install grounding blocks or Ground Loop Isolators? (I did try installing 2 grounding blocks on both main long runs and it didn't change the signal levels at all)

Thanks,

Jason

egnlsn's Avatar egnlsn 08:13 AM 11-23-2008
EXACTLY what is your wiring configuration and how are your HD outlets connected? EXACTLY how is your cable modem connected. You talk about main runs and secondary runs. Please explain.
jasnn's Avatar jasnn 09:04 AM 11-23-2008
Quote:
Originally Posted by jasnn View Post

The CATV distribution is in the attic and consists of the CATV input running about 30 feet to a Viewsonics 2 way splitter, which fed at first, 2 Viewsonics VSMA-608C-10R 8 way drop amps.

Quote:
Originally Posted by jasnn View Post

The main TV/Tivo, is a longer run of cable, about 100 feet, as opposed to 50 feet for the secondary location. All of these runs are brand new quad shielded RG6. This main run does go under the house, as opposed to the secondary run which goes through the attic.

Quote:
Originally Posted by jasnn View Post

I then swapped out one of the Viewsonics VSMA-608C-10R 8 way drop amps, for a VSMA-604C-10R 4 way drop amp, for just the long distance runs.

Quote:
Originally Posted by jasnn View Post

There are no splitters anywhere else. My cable modem signal values are Downstream SNR 33.403dB, Power 6.3dBmV, and Upstream 22.4 dBmV now, coming off of a port on the VSMA-604C-10R.

Thanks
egnlsn's Avatar egnlsn 09:34 AM 11-23-2008
What are the primary vs secondary runs? Is that just a second line run from the distribution point to the same outlet via a different pathway?

The 2 HD sets are 100 & 50 feet from your distribution point. How far are the other outlets?
BTT917's Avatar BTT917 10:11 AM 11-23-2008
1. It's always better to amplify the purest (highest) signal possible, but a 2-way splitter before the amps should be fine unless you are starting with a low signal into the house.

2. For safety purposes, grounding once at the entry point of the home is all that is needed. Keep in mind any place where there is a cut in the line for additional grounding blocks, couplers, amps, etc., is a place for interference to enter.

3. Again, the more cuts in the line, the worse. So there should be a straight, unbroken wire (s) run from the amp to the main room.

Also, are you using 12 cable jacks in the home? If not, count how many you are using: you may be able to elimate the 2 way splitter (adding 3.5dB to the signal in the process) and use just the one 8 way amp.

Check all terminations at all points, even behind the wallplates, as well.

Have you tried disconnecting all other lines except the problem lines temporarily, just the main feed into the 4 way amp out to the main room, to see if giving it the best posible signal will fix/help the problem?
jasnn's Avatar jasnn 10:16 AM 11-23-2008
Any reference to main runs means the dual runs of rg6 cable that I ran for the TV/Tivo in the main TV room, where we watch TV most of the time. The secondary runs referenced are the dual runs of rg6 that I ran for another TV/Tivo that is in another room, where we occasionally watch TV.
egnlsn's Avatar egnlsn 10:21 AM 11-23-2008
Quote:
Originally Posted by jasnn View Post

Any reference to main runs means the dual runs of rg6 cable that I ran for the TV/Tivo in the main TV room, where we watch TV most of the time. The secondary runs referenced are the dual runs of rg6 that I ran for another TV/Tivo that is in another room, where we occasionally watch TV.

Ok, got it. The main run (100') is HD 1 and the secondary run (50") is HD 2. What is the distance from the distribution point to the other outlets?
egnlsn's Avatar egnlsn 10:25 AM 11-23-2008
Quote:
Originally Posted by jasnn View Post

Any reference to main runs means the dual runs of rg6 cable that I ran for the TV/Tivo in the main TV room, where we watch TV most of the time. The secondary runs referenced are the dual runs of rg6 that I ran for another TV/Tivo that is in another room, where we occasionally watch TV.

By dual runs, do you mean that you are using one cable for the TV set and the other for the TiVo, with both cables connected to the same splitter in the attic? As BTT917 asked, how many locations do you need to feed?
jasnn's Avatar jasnn 10:38 AM 11-23-2008
Quote:
Originally Posted by BTT917 View Post

Have you tried disconnecting all other lines except the problem lines temporarily, just the main feed into the 4 way amp out to the main room, to see if giving it the best posible signal will fix/help the problem?

Thank you very much. All of your suggestions and information are helpful to me. I do in fact need all 12 runs, (I outgrew my original 8 way splitter when I needed to add outlets to 2 new rooms). While we don't watch TV in all rooms/outlets at the same time, this is my home wiring design/setup, so I will need to fix this problem. BTW, these cable runs go straight from my drop amps to the various wall outlets.

I will test this setup by removing all other runs, and the splitter, and try the main feed into the 4 way drop amp, terminate 2 of the outputs and see if that boosts my signal levels on the dual run to my main TV/Tivo. If that fixes it, then I assume I'll probably need to look at boosting the signals on my overall setup. It is strange that my signal levels are fine with the current setup on the secondary TV. It's just the one set of runs to the main TV that are a problem.

If I were to go to a single amp setup to a 12 way or 16 way splitter, does anyone have a recommendation for a good quality 20db or better amp with active return technology (so I can hook up my cable modem to it)? Does something like the the Tru Spec CA-30/870AR work out for my use? Specs are at;

http://www.mjsales.net/pdf/CA-30-870AR.pdf

Thanks
emcgrath's Avatar emcgrath 05:04 PM 11-23-2008
I would consider the electroline 8 way drop amp. I would follow that with as many 2 way splitters as you need (no cascading, though). This will give you the same signal at each tv as is coming in the house. The cable company will guarantee that this will work.
egnlsn's Avatar egnlsn 11:13 PM 11-23-2008
I would do this:
LL
emcgrath's Avatar emcgrath 07:20 PM 11-24-2008
egisn's plan will work fine (as long as you've got a solid signal of 9dBmv coming in the house).I just prefer mine because the signal strength to and from the cable modem is more robust-meaning that it'll still work if your cable signal is not up to snuff. I know too many cable guys to trust the signal implicitly. If the cable signal coming in is 0db then my plan will still work. Either way is likely to be just fine.
jasnn's Avatar jasnn 09:40 AM 11-28-2008
I should restate that the tiling problem I'm having is very slight. It only affects 1 location, only some HD channels at that location, and it only seems to exhibit itself through the Tivo, and not through the CATV direct input on the TV. It's for that reason that I'm not inclined to change my overall CATV wiring/amplification setup. As I've said before, a secondary TV/Tivo's reception here, which is in another room, is perfect. Also both Viewsonics VSMA-10R 4 way and 8 way drop amps, provide 0 db of return path insertion loss, just like the EDA-FT08100.

I tried isolating the cabling in the house to just the CATV input direct to my 4 way drop amp, thereby removing the single 2 way splitter and the 8 way drop amp from the system entirely. This 4 way drop amp feeds the 2 primary direct runs to my main TV/Tivo, my cable modem, and a single direct run to my office (not for the cable modem). The result was that it did not increase the signal levels to the main TV/Tivo, and it didn't noticeably decrease the tiling effect seen on the previously mentioned channels.

So I've now purchased some high quality quad shield RG6, (CommScope 5781), and I am going to replace these 2 long runs with it. I'm also going to run them along a different route under the house, to remove the possibility I am running the cable against something that's interfering with the signal. Hopefully that will resolve my last few system gremlins.

Thanks..
jasnn's Avatar jasnn 01:34 PM 12-07-2008
In case anyone else finds this thread and they have a similar problem..

I found my problem, and it had nothing to do with the catv amplification and wiring throughout the house. It had to do with the 3 foot coax cable connecting my wall plate to my Tivo. I replaced it, and my signal values on the problem channels went up, and my tiling problems on those same problem channels all cleared up. In hindsight, I should have tried swapping out that cable first..

..
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