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Thread: Regal tap used on modem-only connection?

  1. #1
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    Regal tap used on modem-only connection?

    Hello all. First post.

    Some friends asked me to come over and change the default password on their new cable internet installation, with an Arris wireless modem. Prior to this, no cable was present at their place.

    After I did, I noticed a Regal ZDRDCT10-6 on the line, with the modem on the TAP leg, and nothing on the OUT leg... not even a 75-ohm terminator. I asked them why it was there, and they said the install tech said it was to boost the signal to the modem, because it was too weak. I said that was an impossibility, and removed it.

    I checked down & up speeds prior to and after removing the tap, and there were no differences. They have since said it seems there are some issues downloading things. Now I'm left wondering if it's just coincidence, or if the tech explained it backwards, and if the signal was too strong.

    I can check the modem the next time I'm over there, but I don't know what parameter(s) to look for as far as optimum signal levels go; but, if in fact the tech used this to reduce too strong a signal, shouldn't he have used a 75-ohm terminator cap on the OUT leg?

    Thanks in advance for any advice.

    -Eddie
    Last edited by EddieS; 01-12-17 at 05:17 PM.

  2. #2
    Administrator Philip's Avatar
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    Hello EddieS, welcome to SG.

    You are correct that a tap simply reduces the signal level, ~1db on the TAP leg, and the other ~6db on the OUT leg. Not all techs would carry or install terminators, so I wouldn't be surprised too much about that. You can add one if you'd like, it is probably better. It is also possible that they used it as a coupler, if they didn't have one handy or there is the possibility of splitting for TVs at that location at some other point in time (as it would introduce similar small signal loss on the TAP leg as a coupler).

    As to the signal levels, you can login to the modem's stats page and look at them, here is a quick guideline of what they should be: http://www.speedguide.net/faq/what-c...idered-good-78
    Basically, your downstream power should be close to zero, anything higher than +7db will be better of with some type of splitter/tap on the line before the modem.

  3. #3
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    Thanks for the info, Phillip. I checked their status, and it was +5.2 to +5.8 down, mid-upper 40s up. I added the tap, and the down went to -1.8 to -0.8, but up didn't really change. So I left it on. It seems their signals were within the acceptable range without the tap, so I don't think it had anything to do with what they perceived as troubles downloading, but, nonetheless, the signal levels are better now.

    I tested my connection, and my own downs are +5.4 to +6.8, and 37.3 to 37.8 up. Mine are worse than theirs were (without the tap), but I've never noticed a problem; however, I'll allow that there might be recent changes to the cable infrastructure, and they may be increasing power as they have expanded, resulting in my current status. I'll add a splitter or two (I don't have any in-line attenuators or taps), and see if I can get the down closer to 0, and hope that my up gets to an acceptable range; then, after finding the right amount of padding, I'll order an inline attenuator to my system.

    Thanks so much for the help!
    Last edited by EddieS; 01-14-17 at 12:59 PM.

  4. #4
    Administrator Philip's Avatar
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    Keep in mind that it may fluctuate somewhat, as long as it is within the acceptable range I wouldn't mess with it much, you most likely won't notice a difference. Once you are outside the +-8db range, some more sensitive modems may not like it.

  5. #5
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    Phillip-

    Well, I couldn't leave well enough alone. I have to experiment. It's how I'm built. I got in the stuff I ordered:

    3dB Holland in-line attenuator;
    6dB Holland in-line attenuator;
    6dB Holland DC/tap (6dB on TAP leg/2.3dB on OUT leg)

    Using each of these, alone and in various combinations, I was able to attenuate the signal from 2.3dB on up. I settled in on the 6dB in-line attenuator, as it gave -1.2 to +0.2 during heavy use hours, and -0.7 to +0.8 during light use hours. Up was 43.5 to 43.8 consistently. This was from +5.4 to +6.8 down and 37.3 to 37.8 without any attenuation. The 3dB attenuator + OUT leg on the DC/TAP (5.3dB total attenuation, + a fraction for the jumper) gave better results during heavy use hours, but I like the cleanliness of just the single attenuator. But that, too, is subject to change...

    Thanks for the help.

    -Eddie

  6. #6
    Administrator Philip's Avatar
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    Strong downstream signal can also simply be brought down with a splitter ... but ok.

    In your case, adding that 6dB attenuator quiets the downstream power to a more "perfect" state, however at the "expense" of also increasing the necessary upstream power. That is good in your case (a very low upstream power/quiet signal can suffer in the presence of any temporary noise spike, ideally upstream power should be 41-45dBmv imho).

    Looks good to me...

    If your upstream power ever gets higher than 45dB, I would swap down to the 3dB attenuator.

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