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Thread: Cable modem problems.

  1. #1
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    Cable modem problems.

    I live in Lugoff, SC and have cable modem service (internet only) with Truvista. When it was first installed, it worked great, no problems at all, I got nearly 30 Mbps, and all was good. I had a problem probably 6 months ago with the connection starting out fast, and then dropping to nothing then slowly picking back up. I called a tech out, and he did something, and it started to work good again, nearly 30 Mbps. About 3 months ago, it started doing something similar, except the connection seems to completely drop out some times for 30 seconds to a minute and then come back. I've called tech support a total of 4 times now I think, I've emailed them at least 4 times, and I've even driven to the office and told them I wasn't leaving until I got a 10 db attenuator (more on that in a second) to no avail, as they didn't know what I was talking about. So previous to that visit I started researching specs, and all that fun stuff, and started watching my signal levels and screenshoting them so I could take them with me to try to confront a tech, considering the only answer I can get is "you don't need a tech, your signals are fine." My upstream goes from 24.75 dBmV to ~32 to 33 dBmV during the day generally. My downstream levels were varying from 6 dBmV to around 9 and 10 dBmV. It seems my upstream levels are slowly dropping over time at night, because at one point I thought a 10 db attenuator might fix my problem, I now think there is a larger problem at play, but they refuse to send a tech out, because during the day its within spec, and I've yet to actually see a technician. I'm at a loss here as to what to do. Any help on what to do would be great.

    Another interesting fact is that I only pay for 15 Mbps service, and on speed tests I was getting nearly 30, then 20s, now 14s if I'm lucky. Randomly I'll get anywhere from 4 Mbps to 7 Mbps with ping times in the 100s. Its pretty annoying.

  2. #2
    Administrator Philip's Avatar
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    Your upstream level seems too low to me. I am not a cable tech, but from what I know it may indicate a tap/node problem, not at your end.

    The upstream power should be between 37-55dbmV. When it is too high, it means there is a lot of noise on the line, and your modem has to speak very 'loud' to be heard on the other end. When it is very low, it means the line is very clean (no noise), so your modem is 'whispering'. When it is whispering, the slightest interference/noise can introduce packet loss and connectivity issues, that's why they recommend to keep it over 37dbmV in general.

    I would just add a splitter in front of the modem (reduces both the downstream power, and somewhat the upstream, by 3.5db for 2-way, 7db for a 4-way), and keep complaining to your cable company. That upstream level is too low, they need to install a "return path attenuator", that would increase your cable modem upstream power. The issue is you want it far from your modem, i.e. if you buy one and install it yourself, put it outside the house, not by the modem. The best thing you can do on your own is install a splitter, or an attenuator, but I would put an attenuator far from your modem upstream. If you want to only increase the upstream power, use a "return path attenuator", it only attenuates the low frequencies used for upstream traffic.
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