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Spiritwalker, or anyone who might shed light

Discussion in 'Other Stuff' started by QUALTHWAR, Dec 7, 2005.

  1. QUALTHWAR

    QUALTHWAR Baitshop opening soon.

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    I know you’re involved with internet issues, but do you know anything about cabling? I’ve had cable TV (time warner / brighthouse) for years and at every place I’ve lived in, the picture quality gets bad (fuzzy) on higher channels. Channel 64 shows a little degradation, channel 71 shows more, and 75 shows even more.

    When the contractors were hooking up the cable before we moved in, they had some question that required a field supervisor to drop by our place. While he was here, I mentioned the bad reception on the higher channels and he said that it was from “bad cabling.” I mentioned to the installer that I put a 10db booster inline in another place we had and that helped. He said not to do that.

    If this was an isolated problem, I wouldn’t think anything of it, but I get the feeling that this is something out of their control and they BS the customer and try to tell them the picture is better after they come out when it really isn’t.

    Do you have any idea why the picture quality degradates on the higher channels?

    Now, I assume that it’s probably related to a db loss somewhere. The lower channels might use a frequency where the db signal loss is mitigated, but this is just a guess. I just don’t trust my cable company.

    When we recently moved, I spoke with a lady about transferring our service and she was really nice and said we wouldn’t be charged for the cable transfer, no charge for hooking up 4 TV cables, and that she’d give us an introductory price on our cable. Well, they were supposed to hook up 4 TV lines and one internet line. One TV line was supposed to run alongside the internet line, but what they did was just run the internet line without the TV line. I had to temporarily add in the fourth TV line.

    They were supposed to come out the next day and bury the cable next to the building and dug under the drive and run a new cable from the pole to the box on the building. That was in August and they never came back out.

    When I called today to have them bury the cable, dig under the drive, fix the reception, and run the fourth line like they were supposed to, the rep wanted to charge me to finish up the fourth line. He said the reason why they only ran 3 lines was because if they ran 4, they would charge for that fourth line. Man, insult my freakin’ intelligence, won’t you. I asked to speak with a supervisor and they quickly rectified that issue. I had the paperwork showing 4 lines plus one cable line.

    The guy coming out tomorrow is supposed to see why the reception is bad. He’s not an installer, so he’s not supposed to hook up a fourth line or dig under the drive to run a new line. I told them about the supervisor saying it was bad cabling and that I had to run a temporary fourth line myself. I said if it’s from bad cabling, maybe we should wait and see if the problem is corrected after the fourth line is professionally installed and they run the new line under the drive. Ha, no, they are going to do things ass-backwards.

    Is there a way for them to check the db levels on separate channels, or can they only check one, overall signal coming in? I want to make sure they fix all these problems and not try to BS me again.
     
  2. SpiritWalker

    SpiritWalker Tattooed Beat Messiah / Prime Mover

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    That’s a super hard thing to comment on, but I will try. Poor SNR (sound to Noise Ratio - How much signal the modem is getting compared to noise. The higher this number is, the better. As this number goes down, it means there is more and more noise in the line. ) is the normal common issue for poor Cable TV and slow poor cable modem connections. Usually this is caused by bad shielding, R59 cabling, or bad connectors/wall plates. It's not easy to determine the location of interference.

    Lower channels being fuzzy, would be an issue with the Upstream here, and Fuzzy higher channels would be on the downstream side.

    A 10db booster would not be what I would recommend in your home. If you put it on the same line as your cable modem, your internet connection will go to crap. And 10db is a HUGE difference.

    Best way to trouble shoot your issue would be to take a portable or small tv and connect it on the outside of your house to the groundblock (the cable bock on the side of your house) and see if you still have the issue. If you do, connect it directly to the tap at the street (easy to do if your cabling is underground)

    You can also check your own RF that is reaching your cable modem. Try going to http://192.168.100.1 (the internal page to most cable modems. If you are prompted for a user name and password, use admin/password or administrator/password. That will allow you to access your cable modem if your company doesn’t block access.
     
  3. QUALTHWAR

    QUALTHWAR Baitshop opening soon.

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    I found some information buried on this page: http://www.hometech.com/learn/video1.html

    This is the info that I thought was relevant:
    RF cables are designed to carry RF signals from one point to another, not from one point to many. In other words, you can't run RF signals to multiple locations by wiring all the destinations in parallel. The reason is that the residential RF distribution scheme is based on 75 ohm terminated transmissions. Meaning that the transmitting side expects to see one, and only one, 75 ohm load on the other end of the cable.

    Then they go on to say:
    A splitter is a small device that has one input (the 75 ohm load) and 2 or more outputs, each driving a separate 75 ohm load. Essentially they are transformers that split the power in the input signal to multiple outputs, while maintaining the 75 ohm impedance. However, there is no free lunch! Every time you split an RF signal with a splitter, you drastically decrease the signal's strength. An RF signal only has so much power. Logic dictates that splitting this signal in two with a "passive" device will result in two signals that each have--at most--half of the original signal's strength.

    Well, we have splitters all over the place. In addition, I have cable wire that I’ve cut and modified and I’m not sure how good the shielding is, or even how good the cable quality itself is. Some of this cable is thinner than the professional cable.

    Then they go on to talk about calculated signal loss. This info here I found very interesting: The optimum level at the wall-plate is between 8 and 15 dB.

    And they say people should have about a 15 db signal coming into their place.

    I have a tangle of splitters and I don’t feel like looking at their configuration at the moment, but it looks like I have, at the very least, a splitter going to another splitter. Using the signal lose rule of thumb they have on the page, they say this:

    2-way splitter = 4 db loss
    And: 100 ft RG6 cable = 4 db loss

    There’s probably at least 100 foot of cable in this place. If I add things up I get:
    100 ft cable = 4db, 2 splitter at 4 db each = 8 db. That’s a total of 12 db signal loss right there, and I’m staying on the conservative side. We actually have at least 3 splitters. If I have 15db coming in and lose 12db, I’m down to just 3db signal strength.

    When I added the 10db amp in another house we had and that greatly helped the picture, I might have boosted the signal back up to the 8-15db range. Still, this doesn’t explain why the lower channels have good reception and the higher numbers degrade. I’m going to check into the upstream/downstream stuff you mentioned and see if I can find anything that explains the reception difference. Maybe I'll just call one of my old instructors if I can. I think I threw away all my electronics books.

    I thought about doing the TV troubleshooting thing like you mentioned, but I’m just going to let the guy use his meter and tell me what signal strength he gets.

    One last thought: The guy says this on this page: Logic dictates that splitting this signal in two with a "passive" device will result in two signals that each have--at most--half of the original signal's strength.

    But then he has the table to calculate signal loss through a splitter and in that table he says you get about a 4db loss with a 2-way splitter. So, in one spot he says the signal will be half at best, and in another spot he says you lose 4 db. Well, half of 15db is 7.5db, and that doesn’t add up to 4 db, so I don’t know what to believe.
     
  4. GoAt

    GoAt Never wrong

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    how long till rukee posts here?
     
  5. ReD_Fist

    ReD_Fist New Member

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    all the "db" stuff is log10 I believe, and is all based off of 75 ohm, like in audio it's a 600 ohm.
    So the "signal" can be calculated separate from the actual "electricity" flowing through ,wire,cacle, connectors. ie ohms law need not apply,specialy for RF.
    The reason for all this audio "3db" stuff is because our ears hear a change in 3db steps, mabye it was log2.
     
  6. Bot_40

    Bot_40 Go in drains

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    db is calculated as 20log10(gain) or something like that iirc
     
  7. QUALTHWAR

    QUALTHWAR Baitshop opening soon.

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    Well, the guy came out and pretty much did what I thought should be done, i.e., install a signal booster. The guy who ran all the cabling in the first place told me not to use a booster. Well, if the signal strength is bad from cable length and splitters, it just makes sense to boost it back up with an amplifier.

    I told the guy who just came out that I had this problem before at a house and a cable guy sold me a 10db booster and that fixed the problem. He guy today immediately said, “That will fix the problem.” I told him the one guy said not to use the booster, but he said it needed it.

    He looked at the one I had and said it was old and gave me a new one. Problem solved.
     
  8. QUALTHWAR

    QUALTHWAR Baitshop opening soon.

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    I don’t know how they consider their signal strength. They look at their meter and it tells them some plus or minus number. The guy said the lower channels showed a +2 and the higher channels showed a -12. He said no wonder the higher channels looked bad.

    Now, I’m assuming we didn’t have a 2db signal and a -12db signal, or the channels wouldn’t work at all, or barely. So they must have a range of signal strength as a default and it goes plus of minus from there.

    Oh, SpiritWalker, I’m supposed to have a dedicated internet line, so I don’t know if the booster will affect that or not. I just did a modem download test by typing in the word “test” in my URL and downloaded a 50M file from my ISP; the speed seems the same as before.
     

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