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Increasing Cable TV signal strength

Discussion in 'Electronic Repair' started by amdx, Feb 8, 2012.

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  1. amdx

    amdx Guest

    Hi All,
    I'm on a boat, about 170ft from the utility post.
    Recently our cable company switched to the wonderful world of
    Digital TV. I got the new digital converter and had no picture.
    I took the box back and got a second box, still no picture. So now I
    suspect a weak signal and confirm that it is the cable length. The cable
    company came out and gave me a better cable than I had installed. At
    this point I have a picture but it is intermittent. The signal at the
    utility post has 3 outputs and had a four way splitter, I suggested the
    cable guy put in two 2 way splitters and give me the stronger (first) tap.
    That got my signal to work almost all the time. I'd like to get the
    signal to work 100% of the time.
    I don't has access to electricity at the utility post, so an amp is
    out. Although I could try an amp at the cable box end. Is that reasonable?
    I would run two cables if there was a way to make it increase signal
    strength.
    Getting anymore from the cable company is not an option.
    Any ideas to get a better signal?
    Mikek


    PS.

    When the signal fails it seems channel 41 is ok and above 42 it breaks up.
    Curious to know if there is an unusual frequency jump between those two
    digital channels.
     
  2. Ian Jackson

    Ian Jackson Guest

    Despite your long 170ft drop cable, were you getting good analogue
    signals before the change to digital? If so, it could be that something
    is not right. Normally, even if you have had only fairly mediocre
    analogues, the digitals are good.

    Otherwise....
    It sounds like your signals are just too weak. As things are, and if you
    can, the obvious fix would be to overcome the substantial loss of the
    170ft drop cable by fitting an amplifier at or near the utility post
    (not at your end), and power it with low voltage via the coax from your
    end (ie similar to a line-powered masthead antenna amplifier). However,
    you would need to consult with the cable company to see if they were OK
    with letting you do this. It could be that they might be able advise you
    on the most suitable amplifier to use. It's not rocket science, but you
    have to be a little careful not to break any of their rules and
    generally do anything they don't approve of.
     
  3. mike

    mike Guest

    Are you sure it's a signal strength problem?
    The cable guy should have been able to measure the signal at your cable box.
    Are the people using the other taps having problems?
    If you're on a boat, you might be at the end of the cable run.
    In that case, you might be able to get them to crank up the gain in their
    distribution amp.
    Power at the pole is not a problem. You can get amps that are powered
    through the signal cable to your cable box. Getting them to let you
    install it
    is another matter.
    You can get MUCH better wire, for a price.

    Signal strength is not the only problem with digital TV.
    Reflections in the system can confuse the decoder. Are there
    any unterminated cables on the other taps?

    I have OTA antenna digital TV. Plenty of signal, but reflections
    cause significant drop outs on some channels. More signal won't fix
    that. In fact, I have a variable attenuator to REDUCE signal strength.
    I tweak the signal level for fewest dropouts.


    Might be electrical noise coupled in thru the ground system.

    Bottom line is that you pay the cable company for TV reception.
    It's their responsibility to provide you with a watchable signal.
    You shouldn't have to tell them what to do. They should just FIX it!!
     
  4. amdx

    amdx Guest

    But, analog can be snowy but very watchable, digital an be pixalated
    and stuttering without no sound or often no picture at all.
    I had not thought about a coax powered amp, Thanks.
    Mikek
     
  5. amdx

    amdx Guest

    But that 3bd did get me a more consistent picture.
     
  6. Ian Jackson

    Ian Jackson Guest

    You are quite correct. However, digital is generally capable of working
    to lower signal levels than analogue. It's amazing how rubbishy digital
    signals can be, yet still give perfect pictures - but don't expect
    miracles!
    I see that several others have also suggested a coax-powered amplifier.
    [If the cable company can't give you more signal level, it's the only
    solution.] As suggested, they should be able to provide a suitable
    amplifier and power unit - or at least advise you what to use.
     
  7. amdx

    amdx Guest

    Hey thanks for the part numbers, I'll look into these.
    Mikek
     
  8. amdx

    amdx Guest

    That's helpful. however, I do receive channels up to 484!
    Dang, just noticed "Lesbo Euro Trash: Big Boobs" is on 502, but, it's
    pay per view. :)
    I thought there might be a bigger jump between 41 and 42
    because when 42 was pixelating 41 was always perfect.

    I think I'll try the amp, before spending for better cable.

    I think I just found a work around, The station I wanted, 42
    is repeated on 428 in HD and it doesn't pixelate when 42 does.
    The pixelating problem is rare, only a spall percentage of the time,
    but very annoying. Ah, the wonderful world if Digital TV.
    Mikek
     
  9. amdx

    amdx Guest

    Yes, it is the loss in the cable.
    No other problems, I'm just way down the dock from them.
    Next time they are around I'll ask.
    Yes that is possible, There are transients in and out so sometimes the
    taps are used and sometimes not. I suppose I could make a bunch of 75
    ohm terminations, and put on a new one every time it's needed.
    However I never noticed a correlation between boats in and boats out.

    Ya, but no. It's in a marina and the marina has a deal with the cable
    company.
    At this point there is talk about putting up an antenna.
    The marina has ten cable boxes for transients that need to be plugged in
    and connected (I guess keep them updated). So it has become a hassle for
    the marina handle the boxes. I just want to lay low and not rock the boat.
     
  10. Sal

    Sal Guest

    I take respectful exception to that last sentence. My digital cable box is
    about 130 cable-feet from the pole. My signal is tapped enroute for digital
    telephone, tapped enroute for Internet and then split (by me) so I can feed
    analog signals via a disttribution amp serving bedrooms, kitchen and shack.
    I get enough from the pole tap to do the job.

    Somebody is treating you badly -- maybe the cable company, maybe the marina.
    Yes, the approach for you to buy and install an inline, remote-power amp at
    the pole is entirely valid, technically. However, that's not in keeping
    with reasonable expectations. You needn't roll over so easily. It's
    supposed to work.

    What -- Are you worried you might offend somebody? That "somebody" seems
    quite okay with kicking you in the ankle. Or elsewhere.

    "Sal"
     
  11. Joerg

    Joerg Guest


    Looks like the cable guys screwed up.

    a. They should be putting enough signal on that cable to overcome the loss.

    b. They should be able to measure the amplitude of pilot signals at your
    end of the cable and tell you how much above minimums they are.


    If all else fails you may need an amp. What Fred means with drop amp is
    usually called a "mast preamplifier", like this:

    http://www.amazon.com/Uhf-Vhf-Anten...EQ/ref=sr_1_20?ie=UTF8&qid=1328748729&sr=8-20

    I don't know this particular one but essentially it should be
    weather-proof. It gets its DC voltage via the coax, from a wall wart
    that would plug in at your boat. So no need to run a power supply cable
    up there.

    Don't go for too much gain. This dreaded DTV falls apart rather easily
    on the slightest distortion or cross-modulation. Not sure if the above
    amp can handle that. You might need a more expensive one. Michael
    Terrell might know which ones are good. What matters is dynamic range.

    Also, make sure you have a perfect 75ohms match at your end. The cable
    box from the cable company should provide that. if you have Internet
    and/or phone through them as well check that connection so it doesn't
    cause reflections. On a boat at sea stuff can corrode quickly.

    Oh, and don't dare to watch that boobs channel while your wife's on the
    boat :)
     
  12. amdx

    amdx Guest

    Now remember the problem is quite intermittent, but seems to be
    happening almost daily for short periods.
    There should be no water in the cable, it's only a couple of months
    old and both ends have crimp on connectors and are located in a box or boat.
    It does have diagnostics, I'm not sure if it is each channel though.
    But I can get some info out of the box. I'll be there Friday and I'll
    get that info and the model of the cable set top box.
    I'm using Comcast at the boat. We are lucky here (I think) in that
    we have a choice of two cable companies.
    Drivel is good.
     
  13. amdx

    amdx Guest

    Any idea where channel 428 would be in that frequency range?
    That's a duplicate of 4,2 but in HD, and it works when 42 doesn't.
    Just a point. I may not have made it clear. I had the tech put in two
    2way splitters and connect me to the first one. Hoping to gain 3db.
    (or 4) and it did make a difference.
     
  14. amdx

    amdx Guest

    Been trying to think of something funny to say about that...
    Best I got is, she would say, "mine look better than those!
     
  15. Joerg

    Joerg Guest


    I believe that's entirely up to the cable company, you'd have to ask an
    engineer there.

    http://en.wikipedia.org/wiki/Digital_cable

    Quote "For example, a cable company might call channel 5-1 "channel 732"
    and channel 5-2 "channel 733"".
    Where does the other leg of that splitter go to? And is that end
    properly terminated?

    [...]
     
  16. I respectfully agree! 8^)

    I don't know exactly how it's done now, but when I worked in the Cable
    industry many moons ago, we had a lot of adjustment we could make. Even
    more, we had variable by frequency attenuators so we could ensure that a
    flat signal showed up. There was a lot of signal at the amplifiers, and
    if we really needed more oomph, we could put in a distribution amp.
    Another amp was really rare.
    Yeah, there is something wrong there. For as much as people hate
    Comcast, when I had cable internet put in, they replaced all the cable
    from the pole to the house, and a lot inside the house. I did talk them
    out of replacing the new cable I had put in, but insisted on putting new
    connectors on them. The measured all the levels and set them high enough
    that I'd be able to add more televisions if I liked.


    Time to call the cable company and tell them you want your MTV.


    - 73 de Mike N3LI -
     
  17. Sal

    Sal Guest


    No way to know from here, but they may not be able to add another amp.

    While I was looking for something else, I lurched into this page:

    <http://www.cisco.com/en/US/products/hw/cable/ps2217/products_white_paper0900aecd800fc94c.shtml>

    While its intended audience is Internet modem designers, the noise
    discussions are informative with regard to other signals, too.

    My point: When you try stringing too many amps in line, the signal-to-noise
    ratio (SNR) eventually becomes unacceptable. (Remember the acceptable SNRs
    cited for 256 QAM and 64 QAM.)

    "Sal"
     
  18. Sal

    Sal Guest

    Sorry. I should have said carrier to noise ratio (CNR), not SNR. SNR
    applies to post-detection signals. i joined the digital world late in life.

    "Sal"
     
  19. Ian Jackson

    Ian Jackson Guest

    Careful! Don't get your dBm mixed up with your dBmV. There's around 48dB
    difference! 0dBm is a massive 48dBmV. That would certainly make most
    set-top boxes wake up and pay attention!
     
  20. amdx

    amdx Guest

    They go to two other outlets, that are used for transient boaters.
    sometimes they are used and sometimes they sit unterminated.
    I have not seen my problem better or worse when boats are in or out.
    But I have several 75 ohm F connector terminations. It's worth a try.
    Mikek
     
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